JP4362857B2 - Light source apparatus and exposure apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light source device and an exposure apparatus, and more particularly to a light source device that emits light of a desired wavelength while controlling polarization of a plurality of light beams, and an exposure apparatus including the light source device.
[0002]
[Prior art]
Conventionally, various exposure apparatuses have been used in lithography processes for manufacturing semiconductor elements (integrated circuits), liquid crystal display elements, and the like. In recent years, as this type of exposure apparatus, a fine circuit pattern formed on a photomask or reticle is reduced and projected on a substrate such as a wafer or a glass plate having a surface coated with a photoresist via a projection optical system. However, a reduction projection exposure apparatus such as a so-called stepper or a so-called scanning stepper, which performs transfer, has become the mainstream because it has a high throughput.
[0003]
However, an exposure apparatus such as a projection exposure apparatus requires high resolution (resolution) with high throughput. The resolving power R and the depth of focus DOF of the projection exposure apparatus are the wavelength λ of the illumination light for exposure, the numerical aperture N.I. A. Using,
R = K · λ / N. A. ...... (1)
DOF = λ / 2 (NA)²        (2)
Respectively represented by
[0004]
  As apparent from the above equation (1), in order to reduce the resolving power R, that is, the minimum pattern line width that can be resolved,(A)Decrease the proportionality constant K,(B)N. A. To increase the(C)Three methods for reducing the wavelength λ of the illumination light for exposure are conceivable. Here, the proportionality constant K is a constant determined by the projection optical system and the process, and normally takes a value of about 0.5 to 0.8. This method of reducing the constant K is called super-resolution in a broad sense. Up to now, improvement of the projection optical system, modified illumination, phase shift reticle, etc. have been proposed and studied. However, there are difficulties such as restrictions on the patterns that can be applied.
[0005]
On the other hand, the numerical aperture N.I. A. The larger the value from Eq. (1), the smaller the resolving power R, but this also means that the DOF becomes shallower as is clear from Eq. (2). For this reason, N.I. A. There is a limit to increasing the value, and about 0.5 is usually appropriate.
[0006]
Therefore, the simplest and most effective method for reducing the resolving power R is to reduce the wavelength λ of the illumination light for exposure.
[0007]
For this reason, g-line steppers and i-line steppers that use an ultra-high pressure mercury lamp that outputs an emission line in the ultraviolet region (g-line, i-line, etc.) as an exposure light source have been mainly used as steppers. Then, a KrF excimer laser stepper using a KrF excimer laser that outputs a KrF excimer laser beam having a shorter wavelength (wavelength 248 nm) as a light source is becoming mainstream. At present, the development of an exposure apparatus that uses an ArF excimer laser (wavelength: 193 nm) as a light source having a shorter wavelength is in progress. However, the above-described excimer laser is large, the energy per pulse is large, optical components are easily damaged, and the use of toxic fluorine gas makes the laser maintenance complicated and expensive. There are disadvantages as a light source of an exposure apparatus.
[0008]
Therefore, using the nonlinear optical effect of the nonlinear optical crystal, a method of converting long wavelength light (infrared light, visible light) into shorter wavelength ultraviolet light, and using the thus obtained ultraviolet light as exposure light. Is attracting attention. As an exposure light source employing such a method, for example, a nonlinear optical crystal in which light from a laser light generation unit equipped with a semiconductor laser is provided in a wavelength conversion unit as disclosed in JP-A-8-334803. An example of an array laser is disclosed in which a single laser element that converts the wavelength and generates ultraviolet light is bundled in a matrix (for example, 10 × 10) to form one ultraviolet light source.
[0009]
[Problems to be solved by the invention]
In the array laser as described above, by bundling a plurality of individually independent laser elements, it is possible to increase the light output of the entire apparatus while keeping the light output of each laser element low. However, since the individual laser elements are independent, in order to match the oscillation spectrum of each laser element, it is necessary to make a fine adjustment and to adopt a very complicated configuration.
[0010]
In view of this, it is conceivable to use a single laser oscillation source, branch the laser beam emitted from the laser oscillation source, amplify each branch beam, and then perform wavelength conversion using a common nonlinear optical crystal. When adopting this method, it is convenient to use an optical fiber for routing the laser light, and a configuration in which a plurality of light beams emitted from a plurality of bundled optical fibers is incident on the nonlinear optical crystal, It is optimal from the viewpoints of simplicity of structure, reduction in output beam diameter, and maintainability.
[0011]
In addition, in order to efficiently generate double harmonics and the like by nonlinear optical effects using a nonlinear optical crystal, linearly polarized light in a specific direction corresponding to the crystal direction of the nonlinear optical crystal is applied to the nonlinear optical crystal. It is necessary to make it incident. However, it is generally difficult to align the directions of linearly polarized light emitted from a plurality of optical fibers. This is because, even if a polarization-maintaining fiber is used and linearly polarized light is guided, the optical fiber has a substantially circular cross-sectional shape. This is because it cannot be specified.
[0012]
The present invention has been made under the above circumstances, and a first object of the invention is to provide a light source device capable of generating predetermined light while controlling the polarization state with a simple configuration. is there.
[0013]
A second object of the present invention is to provide an exposure apparatus that can efficiently transfer a predetermined pattern onto a substrate.
[0014]
[Means for Solving the Problems]
  The light source device of the present invention includes: a plurality of optical fibers; a polarization adjusting device (16D) that aligns the polarization states of a plurality of light beams having the same wavelength via the plurality of optical fibers; Polarization direction conversion device (162) for converting a light beam into a plurality of linearly polarized light beams having the same polarization directionA light amount control device that controls the amount of light emitted from the plurality of optical fibers by individually controlling on / off of the light output from the plurality of optical fibers, the light source device comprising: Each of the optical fibers is an optical fiber in which the amplification target light is guided, constituting an optical fiber amplifier that uses the plurality of light beams incident on the plurality of optical fibers as amplification target light.It is a light source device.
[0015]
  According to this, after the polarization adjusting device aligns the polarization states of the plurality of light beams emitted from the plurality of optical fibers, the polarization direction conversion device converts all the light beams through the plurality of optical fibers to the same polarization direction. Therefore, a plurality of linearly polarized light beams having the same polarization direction can be obtained with a simple configuration.Also, since the light incident on each optical fiber is amplified and emitted from each optical fiber, a plurality of straight lines each having high intensity and the same polarization direction are emitted as light emitted from the polarization direction converter. A polarized light beam can be obtained. As a result, the amount of emitted light as the light source device can be increased.
[0016]
In the light source device of the present invention, when the polarization adjusting device makes the polarization state of each of the plurality of light fluxes through the optical fibers substantially circularly polarized, the polarization direction changing device has a quarter-wave plate (162). ). In such a case, since each of the plurality of light beams through each optical fiber is substantially circularly polarized by the polarization adjusting device, all of the plurality of light beams are passed through the quarter wavelength plate of the polarization direction conversion device. Thus, it can be converted into a plurality of linearly polarized light beams having the same polarization direction. Therefore, it is possible to convert a plurality of light beams into a plurality of linearly polarized light beams having the same polarization direction while making the polarization direction converting device a very simple configuration of one quarter wavelength plate. The polarization direction of linearly polarized light is determined by the direction of the optical axis of the crystal material or the like that forms the quarter wavelength plate. Therefore, by adjusting the direction of the optical axis of the crystal material or the like forming the quarter wavelength plate, a plurality of light fluxes having arbitrary identical linear polarization directions can be obtained.
[0017]
Here, when the optical fiber has a substantially cylindrically symmetric structure, the polarization adjusting device can be configured so that the polarization state of each of the plurality of light beams incident on the optical fibers is substantially circularly polarized. . This is because when circularly polarized light is incident on an optical fiber having a cylindrically symmetric structure, circularly polarized light is emitted from the optical fiber. Since it is impossible to make the optical fiber completely cylindrically symmetric, it is preferable that the length of the optical fiber is short.
[0018]
Further, in the light source device of the present invention, when the polarization adjusting device has an arbitrary polarization state in which all of the plurality of light beams through the optical fibers are almost in the same polarization state, the polarization direction conversion device is The half-wave plate that rotates the plane of polarization and a quarter-wave plate optically connected in series with the half-wave plate can be used. Here, when the half-wave plate and the quarter-wave plate are connected in series, either may be arranged on the upstream side in the optical path. For example, when the half-wave plate is arranged on the upstream side, the polarization planes of a plurality of light fluxes through the respective optical fibers are similarly rotated through the common half-wave plate, and further, Through the common quarter-wave plate, all the light beams become linearly polarized light having the same polarization direction. Also, when the quarter wave plate is arranged on the upstream side, all the light beams can be made into linearly polarized light having the same polarization direction as in the case where the half wave plate is arranged on the upstream side. . Therefore, the polarization direction conversion device can have a simple configuration of one ½ wavelength plate and one ¼ wavelength plate. In this case, a plurality of light fluxes having arbitrary identical linear polarization directions can be obtained by adjusting the direction of the optical axis of the crystal material or the like forming the half-wave plate and the quarter-wave plate.
[0020]
In the light source device of the present invention, each of the plurality of light beams incident on the plurality of optical fibers can be a pulsed light train. In such a case, the light amount of the emitted light as the light source device can be accurately controlled by adjusting the repetition period and pulse height of the light pulse in each pulse light train.
[0021]
In the light source device of the present invention, the light beams that are incident on the plurality of optical fibers are amplified by one or more optical fiber amplifiers (167) before entering the plurality of optical fibers. It can be set as the structure which is. In such a case, it is possible to increase the amount of emitted light as the light source device by the one-stage or multi-stage optical amplification action by one or more stages of optical fiber amplifiers.
[0022]
In the light source device of the present invention, the polarization adjusting device adjusts the mechanical stress applied to each of the plurality of optical fibers arranged immediately before the polarization direction converting device, and enters the polarization direction converting device. Although it is possible to adjust the polarization state of a plurality of light beams, the polarization adjustment device performs polarization adjustment by controlling the optical characteristics of an optical component arranged upstream of the plurality of optical fibers. can do. In such a case, the plurality of optical fibers arranged immediately before the polarization direction changing device are optical fibers having an optical amplifying unit through which the light to be amplified is guided, and are not suitable for polarization adjustment by applying stress or the like. Even in this case, it is possible to align the polarization states of a plurality of light beams incident on the polarization direction changing device by controlling the optical characteristics of the optical component that is more easily adjusted in polarization and is more easily adjusted.
[0023]
In the light source device of the present invention, the plurality of optical fibers may be bundled substantially in parallel with each other. In such a case, the section occupied by the plurality of optical fibers can be reduced, and the light receiving area of the polarization direction conversion device can be reduced, so that the light source device can be reduced in size.
[0024]
The light source device of the present invention further includes a wavelength conversion device (163) that converts the wavelength of the light beam emitted from the polarization direction conversion device through at least one nonlinear optical crystal. Can do. In such a case, the polarization direction of the light beam emitted from the polarization direction conversion device should be set to the polarization direction of the incident light in which the wavelength conversion (double harmonic generation, sum frequency generation) is efficiently performed by the nonlinear optical crystal. Thus, it is possible to efficiently generate and emit light whose wavelength has been converted.
[0025]
Here, the light emitted from the plurality of optical fibers may have either an infrared wavelength range or a visible wavelength range, and the light emitted from the wavelength converter may have an ultraviolet wavelength range. . In such a case, ultraviolet light suitable for transferring a fine pattern can be efficiently generated.
[0026]
In this case, the light emitted from the plurality of optical fibers may have a wavelength near 1547 nm, and the light emitted from the wavelength converter may have a wavelength near 193.4 nm. In such a case, light having a wavelength obtained when an ArF excimer laser light source is used can be efficiently obtained.
[0027]
In the exposure apparatus of the present invention, in the exposure apparatus that transfers a predetermined pattern onto the substrate by irradiating the substrate with the exposure beam, the wavelength converter generates ultraviolet light as the exposure beam generator. An exposure apparatus comprising the light source device (16) of the present invention.
[0028]
According to this, since the light source device that efficiently generates ultraviolet light suitable for transferring a fine pattern is used as the exposure beam generation device, a predetermined pattern can be efficiently transferred to the substrate.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0030]
FIG. 1 shows a schematic configuration of an exposure apparatus 10 according to an embodiment including a light source device according to the present invention. The exposure apparatus 10 is a step-and-scan type scanning exposure apparatus.
[0031]
The exposure apparatus 10 holds an illumination system including a light source device 16 and an illumination optical system 12 and a reticle R as a mask illuminated by exposure illumination light (hereinafter referred to as “exposure light”) IL from the illumination system. Reticle stage RST, projection optical system PL for projecting exposure light IL emitted from reticle R onto wafer W as a substrate, XY stage 14 on which Z tilt stage 58 as a substrate stage holding wafer W is mounted, and These control systems are provided.
[0032]
The light source device 16 is, for example, an ultraviolet pulsed light having a wavelength of 193 nm (substantially the same wavelength as the ArF excimer laser light) or a wavelength of 157 nm (F₂This is a harmonic generator that outputs ultraviolet pulsed light having substantially the same wavelength as laser light. The light source device 16 has a temperature along with an exposure apparatus main body including the illumination optical system 12, the reticle stage RST, the projection optical system PL, the Z tilt stage 58, the XY stage 14, and a main body column (not shown) on which these parts are mounted. The chamber is housed in an environmental chamber (hereinafter referred to as “chamber”) 11 in which pressure, humidity and the like are adjusted with high accuracy.
[0033]
FIG. 2 is a block diagram showing the internal configuration of the light source device 16 together with a main control device 50 that controls the entire device. As shown in FIG. 2, the light source device 16 includes a light source unit 16A, a laser control device 16B, a light amount control device 16C, a polarization adjustment device 16D, and the like.
[0034]
The light source unit 16A includes a pulsed light generation unit 160 as a light generation unit, an optical amplification unit 161, a quarter wavelength plate 162 as a polarization direction change device, a wavelength conversion unit 163, a beam monitoring mechanism 164, an absorption cell 165, and the like. It is configured to include.
[0035]
The pulsed light generator 160 includes a laser light source 160A, optical couplers BS1 and BS2, an optical isolator 160B, an electro-optic modulator (hereinafter referred to as “EOM”) 160C as an optical modulator, and the like. Each element between the laser light source 160A and the wavelength conversion unit 163 is optically connected by an optical fiber.
[0036]
As the laser light source 160A, here, a single wavelength oscillation laser, for example, an InGaAsP, DFB semiconductor laser having an oscillation wavelength of 1.544 μm and a continuous wave output (hereinafter referred to as “CW output”) of 20 mW is used. Hereinafter, the laser light source 160A is also referred to as “DFB semiconductor laser 160A” as appropriate.
[0037]
Here, the DFB semiconductor laser is a one in which a diffraction grating is built in a semiconductor laser instead of a Fabry-Perot type resonator having low longitudinal mode selectivity. This is a so-called distributed feedback (DFB) laser. Since such a laser basically oscillates in a single longitudinal mode, its oscillation spectral line width is suppressed to 0.01 pm or less.
[0038]
Further, the DFB semiconductor laser is usually provided on a heat sink, and these are housed in a casing. In this embodiment, a temperature regulator (for example, a Peltier element) is provided on a heat sink attached to the DFB semiconductor laser 160A. As will be described later, the laser controller 16B controls the temperature to thereby oscillate the wavelength. Can be controlled (adjusted).
[0039]
That is, the oscillation wavelength of the DFB semiconductor laser has a temperature dependency of about 0.1 nm / ° C. Therefore, for example, if the temperature of the DFB semiconductor laser is changed by 1 ° C., the wavelength of the fundamental wave (1544 nm) changes by 0.1 nm, so that the wavelength of the eighth harmonic (193 nm) changes by 0.0125 nm and is 10 times higher. The wave (157 nm) changes its wavelength by 0.01 nm.
[0040]
In the exposure apparatus, it is sufficient if the wavelength of the illumination light for exposure (pulse light) can be changed by about ± 20 pm with respect to the center wavelength. Therefore, the temperature of the DFB semiconductor laser 11 may be changed by about ± 1.6 ° C. for the 8th wave and about ± 2 ° C. for the 10th wave.
[0041]
The laser light source 160A is not limited to a semiconductor laser such as a DFB semiconductor laser. For example, an yttrium (Yb) -doped fiber laser having an oscillation wavelength of around 990 nm may be used.
[0042]
As the optical couplers BS1 and BS2, those having a transmittance of about 97% are used. For this reason, the laser beam from the DFB semiconductor laser 160A is branched into two by the optical coupler BS1, about 97% of which proceeds toward the next-stage optical coupler BS2, and the remaining 3% enters the beam monitor mechanism 164. To do. The laser light incident on the optical coupler BS2 is branched by the optical coupler BS2. About 97% of the laser light travels toward the optical isolator 160B in the next stage, and the remaining 3% enters the absorption cell 165. .
[0043]
The beam monitor mechanism 164, the absorption cell 165, etc. will be described in detail later.
[0044]
The optical isolator 160B is a device for allowing only light in the direction from the optical coupler BS2 toward the EOM 160C to pass and blocking passage of light in the opposite direction. This optical isolator 160B prevents changes in the oscillation mode of the DFB semiconductor laser 160A due to reflected light (returned light), generation of noise, and the like.
[0045]
The EOM 160C is for converting laser light (CW light (continuous light)) that has passed through the optical isolator 160B into pulsed light. As the EOM 160C, an electro-optic modulator (for example, a two-electrode type modulator) having an electrode structure in which chirp correction is performed so that the wavelength broadening of the semiconductor laser output due to chirp with time change of the refractive index is reduced. Yes. The EOM 160C outputs pulsed light that is modulated in synchronization with the voltage pulse applied from the light quantity control device 16C. As an example, assuming that laser light oscillated by the DFB semiconductor laser 160A by the EOM 160C is modulated into pulse light having a pulse width of 1 ns and a repetition frequency of 100 kHz (pulse period of about 10 μs), the light modulation results in output from the EOM 160C. The peak output of the pulsed light is 20 mW, and the average output is 2 μW. Here, it is assumed that there is no loss due to the insertion of the EOM 160C. However, when there is an insertion loss, for example, the loss is −3 dB, the peak output of the pulsed light is 10 mW and the average output is 1 μW.
[0046]
In addition, when the repetition frequency is set to about 100 kHz or more, a decrease in amplification factor due to the influence of ASE (Amplified Spontaneous Emission) noise can be prevented in a fiber amplifier described later. Is desirable.
[0047]
If the extinction ratio is not sufficient even when the pulse light is turned off using only the EOM 160C, it is desirable to use the current control of the DFB semiconductor laser 160A in combination. That is, in the case of a semiconductor laser or the like, the output light can be pulse-oscillated by performing the current control, and therefore it is desirable to generate the pulsed light by using both the current control of the DFB semiconductor laser 160A and the EOM 160C. As an example, by controlling the current of the DFB semiconductor laser 160A, pulse light having a pulse width of, for example, about 10 to 20 ns is oscillated, and only part of the pulse light is cut out from the pulse light by the EOM 160C. Modulate. In this way, it becomes possible to easily generate pulsed light having a narrow pulse width as compared with the case of using only the EOM160C, and it is easier to start and stop the oscillation interval of the pulsed light and the oscillation. It becomes possible to control.
[0048]
Note that an acousto-optic light modulator (AOM) may be used instead of the EOM 160C.
[0049]
The optical amplifying unit 161 amplifies the pulsed light from the EOM 160C, and here includes a plurality of fiber amplifiers. FIG. 3 shows an example of the configuration of the optical amplifying unit 161 together with the EOM 160C.
[0050]
As shown in FIG. 3, the optical amplifying unit 161 includes output units of a delay unit 167 having a total of 128 channels from channel 0 to channel 127 and a total of 128 channels from channel 0 to channel 127 of the delay unit 167. Fiber amplifier 168 connected to₁~ 168₁₂₈And these fiber amplifiers 168₁~ 168₁₂₈Narrowband filter 169 for each of₁~ 169₁₂₈And optical isolator 170₁~ 170₁₂₈Are connected to the final stage fiber amplifiers 171.₁~ 171₁₂₈Etc. In this case, as is clear from FIG._n, Narrow band filter 169_n, Optical isolator 170_nAnd fiber amplifier 171_n(N = 1, 2,..., 128), the optical paths 172 respectively._n(N = 1, 2,..., 128) are configured.
[0051]
The above-described components of the optical amplifying unit 161 will be described in further detail. The delay unit 167 has a total of 128 channels, and gives a predetermined delay time (here, 3 ns) to the output of each channel. is there. In this embodiment, the delay unit 167 includes an erbium (Er) -doped fiber amplifier (EDFA) that amplifies the pulsed light output from the EOM 160C by 35 dB (3162 times), and the output of the EDFA as channel 0. A splitter (flat waveguide 1 × 4 splitter), which is an optical branching means for splitting into four outputs of ˜3 in parallel, and four lights of different lengths connected to the output ends of channels 0˜3 of this splitter. The fiber, four splitters (flat waveguide 1 × 32 splitter) that divide the outputs of these four optical fibers into channels 0 to 31 respectively, and channels 1 to 31 except for channel 0 of each splitter are connected respectively. And 31 optical fibers each having a different length (total of 124). Hereinafter, the 0 to 31 channels of each of the splitters (flat waveguide 1 × 32 splitter) are collectively referred to as a block.
[0052]
More specifically, the pulse light output from the first stage EDFA has a peak output of about 63 W and an average output of about 6.3 mW. This pulse light is split in parallel into four outputs of channels 0 to 3 by a splitter (flat waveguide 1 × 4 splitter), and the delay corresponding to the length of the four optical fibers is given to the output light of each channel. For example, in this embodiment, the propagation speed of light in the optical fiber is 2 × 10.⁸m / s, and optical fibers (lengths 0.1 m, 19.3 m, 38.5 m, and 57.7 m) in channels 0, 1, 2, and 3 of the splitter (flat waveguide 1 × 4 splitter), respectively. Hereinafter, referred to as “first delay fiber”). In this case, the light delay between adjacent channels at each first delay fiber exit is 96 ns.
[0053]
In addition, the channels 1 to 31 of the four splitters (flat waveguides 1 × 32 splitters) have optical fibers (hereinafter referred to as “second delays”) each having a length of 0.6 × N meters (N is a channel number). Called "fiber"). As a result, a delay of 3 ns is given between adjacent channels in each block, and a delay of 3 × 31 = 93 ns is given to the channel 31 output with respect to the channel 0 output of each block.
[0054]
On the other hand, between the first to fourth blocks, as described above, a delay of 96 ns is given to each block by the first delay fiber at the input time of each block. Therefore, the channel 0 output of the second block has a delay of 96 ns with respect to the channel 0 output of the first block, and the delay with the channel 31 of the first block is 3 ns. The same applies to the second to third and third to fourth blocks. As a result, pulsed light having a delay of 3 ns between adjacent channels is obtained at the output end of a total of 128 channels as a total output.
[0055]
Due to the above branching and delay, pulse light having a delay of 3 ns between adjacent channels can be obtained at the output terminals of a total of 128 channels. At this time, the optical pulse observed at each output terminal is modulated by the EOM 160C. 100 kHz (pulse period 10 μs), which is the same as the above pulse. Accordingly, when viewed as a whole laser beam generator, after the 128 pulses are generated at intervals of 3 ns, the next pulse train is generated at intervals of 9.62 μs at 100 kHz. That is, the total output is 128 × 100 × 10^Three= 1.28 × 10⁷Pulse / second.
[0056]
In the present embodiment, an example in which the number of divisions is 128 and a short delay fiber is used has been described. For this reason, an interval of 9.62 μs that does not emit light is generated between the pulse trains. However, by increasing the number of divisions, making the delay fiber longer to an appropriate length, or using a combination of these, It is also possible to make the intervals completely equal.
[0057]
The fiber amplifier 168_nAs for (n = 1, 2,..., 128), here, erbium having a mode field diameter of an optical fiber (hereinafter referred to as “mode diameter”) of 5 to 6 μm (same as that used in normal communication) An Er) -doped fiber amplifier (EDFA) is used. This fiber amplifier 168_nThus, the output light from each channel of the delay unit 167 is amplified according to a predetermined amplification gain. This fiber amplifier 168_nThe excitation light source will be described later.
[0058]
The narrow band filter 169_n(N = 1, 2,..., 128) is a fiber amplifier 168._nAnd the output wavelength of the DFB semiconductor laser 160A (wavelength width is about 1 pm or less) is transmitted to substantially narrow the wavelength width of the transmitted light. As a result, the ASE light is transmitted to the subsequent fiber amplifier 171._nIt is possible to prevent the laser beam from being scattered due to the propagation of ASE noise. Here, the narrow band filter 169_nThe transmission wavelength width is preferably about 1 pm, but the wavelength width of ASE light is about several tens of nanometers. Therefore, even if a narrow band filter having a transmission wavelength width of about 100 pm obtained at this time is used, there is a practical problem. ASE light can be cut to such an extent that there is not.
[0059]
In the present embodiment, since the output wavelength of the DFB semiconductor laser 160A may be actively changed as described later, the output wavelength has a variable width (about ± 20 pm as an example in the exposure apparatus of the present embodiment). It is preferable to use a narrowband filter having a corresponding transmission wavelength width (approximately equal to or greater than the variable width). In the laser apparatus applied to the exposure apparatus, the wavelength width is set to about 1 pm or less.
[0060]
The optical isolator 170_n(N = 1, 2,..., 128) is for reducing the influence of the return light as in the optical isolator 160B described above.
[0061]
The fiber amplifier 171_nAs for (n = 1, 2,..., 128), here, the mode diameter of the optical fiber is used in normal communication in order to avoid an increase in the spectral width of the amplified light due to the nonlinear effect in the optical fiber. An EDFA having a large mode diameter wider than (5 to 6 μm), for example, 20 to 30 μm, is used. This fiber amplifier 171_nIs the fiber amplifier 168 described above._nThe optical output from each channel of the delay unit 167 amplified in step 167 is further amplified. As an example, an average output of 50 μW for each channel in the delay unit 167 and an average output of 6.3 mW for all channels are set to a two-stage fiber amplifier 168._n171_nIf a total of 46 dB (40600 times) is to be amplified, the optical path 172 corresponding to each channel_nOutput terminal (fiber amplifier 171_nAt the output end) of the optical fiber constituting the above, a peak output of 20 kW, a pulse width of 1 ns, a pulse repetition of 100 kHz, an average output of 2 W, and an average output of 256 W in all channels are obtained. The fiber amplifier 171_nThe excitation light source will be described later.
[0062]
In the present embodiment, the optical path 172 corresponding to each channel in the delay unit 167._nOutput end of the fiber amplifier 171, that is, the fiber amplifier 171._nThe output ends of the optical fibers constituting the optical fiber are bundled in a bundle, and a fiber bundle 173 having a cross-sectional shape as shown in FIG. 4 is formed. At this time, since the clad diameter of each optical fiber is about 125 μm, the diameter of the bundle at the output end where 128 wires are bundled can be about 2 mm or less. In this embodiment, the fiber bundle 173 is the final stage fiber amplifier 171._nThe output end of the fiber amplifier 171 is used as it is._nIt is also possible to couple an undoped optical fiber to form a bundle fiber at its output end.
[0063]
The preceding fiber amplifier 168 having a standard mode diameter is used._nAnd the final stage fiber amplifier 171 having a wide mode diameter._nIs connected using an optical fiber whose mode diameter increases in a tapered manner.
[0064]
Next, an excitation light source and the like for each fiber amplifier will be described with reference to FIG. In FIG. 5, the fiber amplifier constituting the optical amplifier 161 and its peripheral part are schematically shown together with a part of the wavelength converter 163.
[0065]
In FIG. 5, the first stage fiber amplifier 168 is shown._nThe semiconductor laser 178 for excitation is fiber-coupled, and the output of the semiconductor laser 178 is input to a doped fiber for a fiber amplifier through a wavelength division multiplexer (WDM) 179, thereby The doped fiber is excited.
[0066]
On the other hand, a fiber amplifier 171 having a large mode diameter._nThen, the semiconductor laser 174 as a pumping light source for pumping the above-mentioned fiber amplifier doped fiber having a large mode diameter is fiber-coupled to a large mode diameter fiber matched to the diameter of the fiber amplifier doped fiber. The output of the semiconductor laser 174 is input to the doped fiber for an optical amplifier using the WDM 176, and the doped fiber is excited.
[0067]
This large mode diameter fiber (fiber amplifier) 171_nThe laser light amplified in step S1 enters the wavelength conversion unit 163, where it is converted into ultraviolet laser light. The configuration of the wavelength conversion unit 163 will be described later.
[0068]
Large mode fiber (fiber amplifier) 171_nIt is desirable that the laser light (signal) to be amplified propagating in the main mode is mainly in the fundamental mode, which mainly selectively excites the fundamental mode in a single mode or a multimode fiber having a low mode order. Can be realized.
[0069]
In this embodiment, four high-power semiconductor lasers coupled to a large mode diameter fiber are coupled from the front and four from the rear. Here, in order to efficiently couple the pumping semiconductor laser light to the optical amplifying doped fiber, an optical fiber having a double clad structure in which the clad has a double structure is used as the optical amplifying doped fiber. desirable. At this time, the pumping semiconductor laser light is introduced into the double clad inner clad by the WDM 176.
[0070]
The semiconductor lasers 178 and 174 are controlled by a light amount control device 16C.
[0071]
In the present embodiment, the optical path 172_nAs an optical fiber constituting the fiber amplifier 168_n171_nTherefore, the difference in gain between the fiber amplifiers causes variations in the optical output of each channel. For this reason, in this embodiment, the fiber amplifier (168 of each channel)._n171_n), A part of the output is branched, and photoelectric conversion is performed by the photoelectric conversion elements 180 and 181 provided at the respective branch ends. Output signals of these photoelectric conversion elements 180 and 181 are supplied to the light quantity control device 16C.
[0072]
In the light quantity control device 16C, the drive current of each pumping semiconductor laser (178, 174) is feedback-controlled so that the optical output from each fiber amplifier is constant (that is, balanced) at each amplification stage. It has become.
[0073]
Furthermore, in this embodiment, as shown in FIG. 5, the light branched by the beam splitter in the middle of the wavelength conversion unit 163 is photoelectrically converted by the photoelectric conversion element 182, and the output signal of the photoelectric conversion element 182 is subjected to light amount control. It is supplied to the device 16C. In the light amount control device 16C, the light intensity in the wavelength conversion unit 163 is monitored based on the output signal of the photoelectric conversion element 182, and the pumping semiconductor laser is set so that the light output from the wavelength conversion unit 163 becomes a predetermined light output. The drive current of at least one of 178 and 174 is feedback-controlled.
[0074]
By adopting such a configuration, the amplification factor of the fiber amplifier of each channel is made constant for each amplification stage, so that an uneven load is not applied between the fiber amplifiers and a uniform light intensity is obtained as a whole. It is done. Further, by monitoring the light intensity in the wavelength converter 163, a predetermined predetermined light intensity can be fed back to each amplification stage, and a desired ultraviolet light output can be stably obtained.
[0075]
The light quantity control device 16C will be described in detail later.
[0076]
From the optical amplifying unit 161 (each optical fiber output end forming the bundle-fiber 173) configured as described above, all of the pulsed light is aligned and output by the polarization adjusting device 16D described later. The pulsed light that is circularly polarized light is converted into linearly polarized light having the same polarization direction by the quarter wavelength plate 162 (see FIG. 2), and is incident on the wavelength conversion unit 163 in the next stage.
[0077]
The wavelength converter 163 includes a plurality of nonlinear optical crystals, converts the wavelength of the amplified pulsed light (light having a wavelength of 1.544 μm) into its 8th harmonic or 10th harmonic, and an ArF excimer laser. Pulsed ultraviolet light having the same output wavelength (193 nm) is generated.
[0078]
FIG. 6 shows a configuration example of the wavelength converter 163. Here, a specific example of the wavelength conversion unit 163 will be described with reference to FIG. In FIG. 6, the fundamental wave having a wavelength of 1.544 μm emitted from the output end of the fiber bundle 173 is wavelength-converted to an eighth harmonic (harmonic) using a nonlinear optical crystal, and is the same as the ArF excimer laser. A configuration example for generating ultraviolet light having a wavelength of 193 nm is shown.
[0079]
6, the fundamental wave (wavelength 1.544 μm) → second harmonic (wavelength 772 nm) → third harmonic (wavelength 515 nm) → fourth harmonic (wavelength 386 nm) → 7th harmonic (wavelength 221 nm) → Wavelength conversion is performed in the order of 8th harmonic wave (wavelength 193 nm).
[0080]
More specifically, a fundamental wave having a wavelength of 1.544 μm (frequency ω) output from the output end of the fiber bundle 173 is incident on the first-stage nonlinear optical crystal 533. When the fundamental wave passes through the nonlinear optical crystal 533, the second harmonic generation generates a double wave of the frequency ω of the fundamental wave, that is, a double wave of the frequency 2ω (wavelength is 772 nm). In the case of FIG. 6A, the linear polarization by the above-described quarter wavelength plate 162 is performed so that the polarization direction in which the second harmonic wave is generated most efficiently in the nonlinear optical crystal 533 is obtained. The setting of the polarization direction of the linearly polarized light is performed by adjusting the direction of the optical axis of the quarter wavelength plate 162.
[0081]
As this first-stage nonlinear optical crystal 533, LiB_ThreeO_FiveAn (LBO) crystal is used, and a method by adjusting the temperature of the LBO crystal, NCPM (Non-Critical Phase Matching), is used for phase matching for wavelength conversion of the fundamental wave to a double wave. NCPM does not cause an angular shift (Walk-off) between the fundamental wave and the second harmonic in the nonlinear optical crystal, so it can be converted to a double wave with high efficiency. This is advantageous because it does not undergo beam deformation due to -off.
[0082]
The fundamental wave transmitted without being wavelength-converted by the nonlinear optical crystal 533 and the double wave generated by the wavelength conversion are given a half-wavelength and one-wavelength delay by the wave plate 534 at the next stage, respectively, so that only the fundamental wave is transmitted. The polarization direction rotates 90 degrees and enters the second-stage nonlinear optical crystal 536. An LBO crystal is used as the second-stage nonlinear optical crystal 536, and the LBO crystal is used in NCPM having a temperature different from that of the first-stage nonlinear optical crystal (LBO crystal) 533. In this nonlinear optical crystal 536, a triple wave (wavelength 515 nm) is generated by sum frequency generation from the double wave generated in the first-stage nonlinear optical crystal 533 and the fundamental wave transmitted through the nonlinear optical crystal 533 without wavelength conversion. )
[0083]
Next, the third harmonic wave obtained by the nonlinear optical crystal 536 and the fundamental wave and the second harmonic wave transmitted through the nonlinear optical crystal 536 without wavelength conversion are separated by the dichroic mirror 537 and reflected there. The third harmonic wave passes through the condenser lens 540 and the dichroic mirror 543 and enters the fourth-stage nonlinear optical crystal 545. On the other hand, the fundamental wave and the second harmonic wave transmitted through the dichroic mirror 537 enter the third-stage nonlinear optical crystal 539 through the condenser lens 538.
[0084]
An LBO crystal is used as the third-stage nonlinear optical crystal 539, and the fundamental wave is transmitted through the LBO crystal without being wavelength-converted. 386 nm). The fourth harmonic wave obtained by the nonlinear optical crystal 539 and the fundamental wave transmitted therethrough are separated by the dichroic mirror 541, and the fundamental wave transmitted therethrough passes through the condenser lens 544 and is reflected by the dichroic mirror 546. Then, the light enters the fifth-stage nonlinear optical crystal 548. On the other hand, the fourth harmonic wave reflected by the dichroic mirror 541 passes through the condenser lens 542 and reaches the dichroic mirror 543, where it is synthesized coaxially with the third harmonic wave reflected by the dichroic mirror 537 and is four-staged. It enters the nonlinear optical crystal 545 of the eye.
[0085]
As the fourth-stage nonlinear optical crystal 545, β-BaB₂O_FourA (BBO) crystal is used, and a seventh harmonic (wavelength 221 nm) is obtained from the third harmonic and the fourth harmonic by sum frequency generation. The seventh harmonic wave obtained by the nonlinear optical crystal 545 passes through the condensing lens 547 and is synthesized by the dichroic mirror 546 coaxially with the fundamental wave transmitted through the dichroic mirror 541 to be the fifth stage nonlinear optical crystal 548. Is incident on.
[0086]
An LBO crystal is used as the fifth-stage nonlinear optical crystal 548, and an eighth harmonic wave (wavelength 193 nm) is obtained from the fundamental wave and the seventh harmonic wave by sum frequency generation. In the above configuration, instead of the 7th harmonic generation BBO crystal 545 and the 8th harmonic generation LBO crystal 548, CsLiB₆O_Ten(CLBO) crystal or Li₂B_FourO₇It is also possible to use (LB4) crystals.
[0087]
In the configuration example of FIG. 6, since the third harmonic and the fourth harmonic are incident on the fourth-stage nonlinear optical crystal 545 through different optical paths, a lens 540 that collects the third harmonic and the fourth harmonic Can be placed in separate optical paths. The fourth harmonic wave generated in the third-stage nonlinear optical crystal 539 has an elliptical cross-sectional shape due to the Walk-off phenomenon. Therefore, in order to obtain good conversion efficiency with the fourth-stage nonlinear optical crystal 545, it is desirable to perform beam shaping of the fourth harmonic wave. In this case, since the condensing lenses 540 and 542 are arranged in separate optical paths, for example, a pair of cylindrical lenses can be used as the lens 542, and it becomes possible to easily perform quadrature beam shaping. For this reason, it is possible to make the overlap with the third harmonic wave in the fourth-stage nonlinear optical crystal (BBO crystal) 545 good and increase the conversion efficiency.
[0088]
Furthermore, a lens 544 that condenses the fundamental wave incident on the fifth-stage nonlinear optical crystal 548 and a lens 547 that condenses the seventh harmonic wave can be placed in different optical paths. The seventh harmonic wave generated in the fourth-stage nonlinear optical crystal 545 has an elliptical cross-sectional shape due to the Walk-off phenomenon. Therefore, in order to obtain good conversion efficiency with the fifth-stage nonlinear optical crystal 548, it is preferable to perform beam shaping of the seventh harmonic wave. In this embodiment, since the condensing lenses 544 and 547 can be arranged in separate optical paths, for example, a pair of cylindrical lenses can be used as the lens 547, and beam shaping of 7th harmonic can be easily performed. Become. For this reason, it is possible to make the overlap with the fundamental wave in the fifth-stage nonlinear optical crystal (LBO crystal) 548 good and to increase the conversion efficiency.
[0089]
The configuration between the second-stage nonlinear optical crystal 536 and the fourth-stage nonlinear optical crystal 545 is not limited to that shown in FIG. 6, and is generated from the nonlinear optical crystal 536 and reflected by the dichroic mirror 537. The third harmonic wave and the fourth harmonic wave obtained by converting the wavelength of the second harmonic wave generated from the nonlinear optical crystal 536 and transmitted through the dichroic mirror 537 with the nonlinear optical crystal 539 are simultaneously incident on the nonlinear optical crystal 545. As long as the two optical path lengths between the nonlinear optical crystals 536 and 545 are equal, any configuration may be used. This is the same between the third-stage nonlinear optical crystal 539 and the fifth-stage nonlinear optical crystal 548.
[0090]
According to the experiment conducted by the inventor, in the case of FIG. 6, the average output of the eighth harmonic wave (wavelength: 193 nm) per channel was 45.9 mW. Therefore, the average output from the bundle including all 128 channels is 5.9 W, and it is possible to provide ultraviolet light having a wavelength of 193 nm and sufficient output as a light source for an exposure apparatus.
[0091]
In this case, an LBO crystal that is readily available as a high-quality crystal as a commercial product is currently used for the generation of the eighth harmonic (193 nm). This LBO crystal has an extremely small absorption coefficient for ultraviolet light at 193 nm and is advantageous in terms of durability since optical damage of the crystal does not become a problem.
[0092]
In addition, an LBO crystal is used with an angular phase matching at a generation portion of an eighth harmonic (for example, a wavelength of 193 nm), but since the phase matching angle is large, the effective nonlinear optical constant (deff) is small. Therefore, it is preferable to provide a temperature control mechanism for the LBO crystal and use the LBO crystal at a high temperature. Thereby, the phase matching angle can be reduced, that is, the constant (deff) can be increased, and the eighth harmonic generation efficiency can be improved.
[0093]
The wavelength conversion unit 163 shown in FIG. 6 is an example, and the configuration of the wavelength conversion unit of the present invention is not limited to this. For example, a fundamental wave having a wavelength of 1.57 μm emitted from the output end of the fiber bundle 173 is generated by using a nonlinear optical crystal to generate a 10th harmonic, and F₂You may decide to generate the ultraviolet light of 157 nm which is the same wavelength as a laser.
[0094]
Referring back to FIG. 2, the beam monitor mechanism 164 is an energy monitor composed of a Fabry-Perot etalon (hereinafter also referred to as “etalon element”) and a photoelectric conversion element such as a photodiode (both not shown). ). Light incident on the etalon element constituting the beam monitor mechanism 164 is transmitted with a transmittance corresponding to the frequency difference between the resonance frequency of the etalon element and the frequency of the incident light, and a photodiode that detects the transmitted light intensity at this time Is output to the laser control device 16B. The laser control device 16B performs predetermined signal processing on this signal, so that information on the optical characteristics of the incident light with respect to the beam monitor mechanism 164, specifically the etalon element (specifically, the center wavelength and wavelength width of the incident light ( Spectrum half width) etc. Then, the information on the optical characteristics is notified to the main controller 50 in real time.
[0095]
The frequency characteristic of transmitted light intensity generated by the etalon element is affected by the temperature and pressure of the atmosphere, and in particular, the resonance frequency (resonance wavelength) is temperature dependent. For this reason, in order to accurately control the center wavelength and the spectral half width of the laser light oscillated from the laser light source 160A based on the detection result of the etalon element, it is necessary to investigate the temperature dependence of the resonance wavelength. is important. In the present embodiment, the temperature dependence of the resonance wavelength is measured in advance, and the measurement result is stored as a temperature dependence map in a memory 51 (see FIG. 1) as a storage device provided in the main controller 50. . Then, in the main controller 50, when the absolute wavelength calibration of the beam monitor mechanism 164 is performed, the resonance wavelength (detection reference wavelength) at which the transmittance of the etalon element is maximized exactly matches the set wavelength. The laser controller 16B is instructed to actively control the temperature of the etalon element in the beam monitor mechanism 164.
[0096]
The output of the energy monitor that constitutes the beam monitor mechanism 164 is supplied to the main controller 50. The main controller 50 detects the energy power of the laser beam based on the output of the energy monitor, and the laser controller 16B. The amount of laser light oscillated by the DFB semiconductor laser 160A is controlled as necessary, or the DFB semiconductor laser 160A is turned off. However, in the present embodiment, as will be described later, the normal light amount control (exposure amount control) is mainly configured by the light amount control device 16C to control the peak power or frequency of the output pulse light of the EOM 160C, or to configure the light amplification unit 161. Therefore, when the energy power of the laser light largely fluctuates for some reason, the main controller 50 controls the laser controller 16B as described above.
[0097]
The absorption cell 165 is an absolute wavelength source for absolute wavelength calibration of the oscillation wavelength of the DFB semiconductor laser 160A, that is, absolute wavelength calibration of the beam monitor mechanism 164. In the present embodiment, since the DFB semiconductor laser 160A having an oscillation wavelength of 1.544 μm is used as the laser light source as the absorption cell 165, an acetylene isotope having absorption lines densely present in a wavelength band near this wavelength. Is used.
[0098]
As will be described later, as the light for monitoring the wavelength of the laser light, the intermediate wave (second harmonic, third harmonic, fourth harmonic, etc.) of the wavelength converter 163 described above together with or instead of the fundamental wave. Alternatively, when selecting light after wavelength conversion, an absorption cell in which absorption lines are densely present in a wavelength band such as an intermediate wave may be used. For example, when the third harmonic wave is selected as the wavelength monitoring light, iodine molecules having absorption lines densely in the vicinity of a wavelength of 503 nm to 530 nm are used as an absorption cell, and appropriate absorption lines for the iodine molecules are used. And select that wavelength as the absolute wavelength.
[0099]
The absolute wavelength source is not limited to the absorption cell, and an absolute wavelength light source may be used.
[0100]
The laser control device 16B detects the center wavelength and wavelength width (spectrum half width) of the laser light based on the output of the beam monitor mechanism 164, and the DFB semiconductor laser so that the center wavelength becomes a desired value (set wavelength). 160A temperature control (and current control) is performed by feedback control. In the present embodiment, the temperature of the DFB semiconductor laser 160A can be controlled in units of 0.001 ° C.
[0101]
Further, the laser control device 16B performs switching between pulse output and continuous output of the DFB semiconductor laser 160A and control of the output interval and pulse width at the time of the pulse output in accordance with an instruction from the main control device 50. At the same time, the oscillation control of the DFB semiconductor laser 160A is performed so as to compensate for the output fluctuation of the pulsed light.
[0102]
In this way, the laser control device 16B stabilizes the oscillation wavelength and controls it to a constant wavelength, or finely adjusts the output wavelength. Conversely, the laser control device 16B may adjust the output wavelength by actively changing the oscillation wavelength of the DFB semiconductor laser 160A in response to an instruction from the main control device 50.
[0103]
For example, according to the former, the aberration (imaging characteristics) of the projection optical system PL due to the wavelength variation is prevented or the variation is prevented, and the image characteristics (optical characteristics such as image quality) change during pattern transfer. Nothing will happen.
[0104]
Further, according to the latter, depending on the altitude difference or atmospheric pressure difference between the manufacturing site where the exposure apparatus is assembled and adjusted and the installation location (delivery destination) of the exposure apparatus, and the difference in the environment (atmosphere in the clean room), etc. Variations in the imaging characteristics (such as aberrations) of the projection optical system PL that occur can be offset, and the time required to start up the exposure apparatus at the delivery destination can be shortened. Furthermore, according to the latter, fluctuations in the aberration of the projection optical system PL, projection magnification, focus position, etc. caused by irradiation of exposure illumination light and changes in atmospheric pressure, etc. can be canceled while the exposure apparatus is in operation. Therefore, it is possible to always transfer the pattern image onto the substrate in the best imaging state.
[0105]
As described above, the light amount control device 16C includes the fiber amplifier 168 in the optical amplifying unit 161._n171_nThe drive current of each pumping semiconductor laser (178, 174) is feedback controlled based on the output of the photoelectric conversion elements 180, 181 that detect the optical output of the optical fiber, and the amplification factor of the fiber amplifier of each channel is set for each amplification stage. Based on the function of making it constant and the output signal of the photoelectric conversion element 182 that detects the light branched by the beam splitter in the middle of the wavelength converter 163, feedback control of at least one drive current of the pumping semiconductor lasers 178 and 174 is performed. A predetermined light intensity is fed back to each amplification stage and a desired ultraviolet light output is stabilized.
[0106]
Furthermore, in this embodiment, the light quantity control device 16C has the following functions.
[0107]
  That is, the light quantity control device 16C
(1)  In response to an instruction from the main controller 50, the fiber output of each channel constituting the fiber bundle 173, that is, each optical path 172._nA function of controlling the average light output of the entire bundle by controlling on / off of the outputs individually (hereinafter referred to as “first function” for convenience),
(2)  By controlling the frequency of the pulsed light output from the EOM 160C in accordance with an instruction from the main controller 50, the average optical output (output energy) of each channel of the optical amplifying unit 161 per unit time, that is, per unit time Each optical path 172 of_nA function for controlling the intensity of the output light from (hereinafter referred to as “second function” for convenience),
(3)  By controlling the peak power of the pulsed light output from the EOM 160C in accordance with an instruction from the main controller 50, the average optical output (output energy) of each channel of the optical amplifying unit 161 per unit time, that is, the unit time Each light path 172 per hit_nAnd a function for controlling the intensity of the output light (hereinafter referred to as “third function” for convenience).
[0108]
According to the first function of the light quantity control device 16C, the average light output (light quantity) of the entire bundle can be controlled in increments of 1/128 of the maximum output light quantity (about every 1% or less). That is, the dynamic range can be set to a wide range of 1 to 1/128. Each optical path 172_nAre configured using the same constituent members, and therefore, each optical path 172 is designed in terms of design._nThe light outputs should be equal to each other, and the light quantity control in increments of 1/128 will have good linearity.
[0109]
In this embodiment, the wavelength converter 163 that converts the wavelength of the output of the optical amplifier 161, that is, the output of the fiber bundle 173, is provided. The output of the wavelength converter 163 is transmitted to each optical path 172._nOutput, ie, fiber amplifier 171_nIn principle, linear control (every 1%) in increments of 1/128 of the maximum output light amount should be possible with respect to the set light amount.
[0110]
In practice, however, each optical path 172 is caused by manufacturing errors or the like._nVariation in the output of each light path and each optical path 172_nSince there is a high possibility that there is a variation in wavelength conversion efficiency with respect to the output of each optical fiber (optical path 172) in advance._n) And output variations due to variations in wavelength conversion efficiency for each optical fiber output, etc., and respond to the on / off status of the optical output from each optical fiber based on the measurement results A first output intensity map that is a map of the intensity of the optical output from the wavelength conversion unit 163 (an output intensity conversion table corresponding to the fiber groove to be turned on) is created, and the first output intensity map is used as the main controller. 50 is stored in a memory 51 attached to 50.
[0111]
In the light quantity control device, when the light quantity control is performed by the first function, the light quantity control is performed based on the set light quantity given from the main controller 50 and the output intensity map.
[0112]
Further, the light quantity control device 16C performs frequency control of the pulsed light output from the EOM 160C in the second function by changing the frequency of the rectangular wave (voltage pulse) applied to the EOM 160C. Since the frequency of the pulsed light output from the EOM 160C matches the frequency of the voltage pulse applied to the EOM 160C, the frequency of the output pulsed light is controlled by controlling the applied voltage.
[0113]
In the present embodiment, as described above, the frequency of the rectangular wave applied to the EOM 160C is 100 kHz. For example, if this frequency is set to 110 kHz, the number of optical pulses output from the EOM 160C per unit time increases by 10%, and this pulse is sequentially transmitted from channel 0 to channel by the delay unit 167 for each pulse as described above. As a result of the allocation to 127 total 128 channels, the pulsed light per unit time increases by 10% even if each channel is viewed, and the optical energy per optical pulse is the same, that is, the peak power of the pulsed light is constant. , Each optical path 172 per unit time_nThe output light intensity (light quantity) increases by 10%.
[0114]
In this embodiment, the wavelength converter 163 that converts the wavelength of the output light of each channel of the optical amplifying unit 161 is provided. The light amount of the output light per unit time of the wavelength converter 163 is a peak. If the power is constant, it is proportional to the frequency of the output pulse of each channel. As described above, the light amount control by the second function is a control excellent in the reality.
[0115]
However, in general, the amplification gain of the fiber amplifier is dependent on the input light intensity. Therefore, if the frequency of the output light of the EOM 160C is changed, the fiber amplifier 168 is changed._n171_nThe input light intensity of the fiber amplifier 168 changes as a result._n171_nIn some cases, the peak power of the pulsed light output from the laser beam may change, so that the above-described linearity is not always obtained. Therefore, in this embodiment, the input frequency intensity dependency of the fiber amplifier output is measured in advance, and the output intensity of the optical amplifying unit 161 (each channel thereof) corresponding to the frequency of the pulsed light input to the optical amplifying unit 161 based on the measurement. The second output intensity map (conversion table of the output intensity of the optical amplifying unit 161 corresponding to the frequency of the output light of the EOM) is created, and the second output intensity map is stored in the memory 51. .
[0116]
The light amount control device 16C performs light amount control based on the set light amount given from the main control device 50 and the second output intensity map when performing light amount control by the second function. ing.
[0117]
The light quantity control device 16C controls the peak power of the pulsed light output from the EOM 160C in the third function by controlling the peak intensity of the voltage pulse applied to the EOM 160C. This is because the peak power of the output light from the EOM 160C depends on the peak intensity of the voltage pulse applied to the EOM 160C.
[0118]
However, as described above, the amplification gain of the fiber amplifier depends on the input light intensity. Therefore, if the peak intensity of the pulsed light output from the EOM 160C is changed, the fiber amplifier 168 is changed._n171_nThe input light intensity of the fiber amplifier 168 changes as a result._n171_nIn some cases, the peak power of the pulsed light output from the sensor changes. Fiber amplifier 168_n171_nAlthough it is possible to suppress this change in peak power by properly designing the optical fiber, other performance such as the optical output efficiency of the optical fiber amplifier may be degraded.
[0119]
Therefore, in the present embodiment, the dependency of the fiber amplifier output on the input pulse peak intensity is measured in advance, and the optical amplifier 161 (each channel) corresponding to the peak intensity of the pulsed light input to the optical amplifier 161 based on the measurement. A third output intensity map that is a map of the output intensity (a conversion table of the intensity of the output pulse light of the optical amplifier 161 corresponding to the peak intensity of the output light of the EOM) is created, and the third output intensity map is stored in the memory 51. This third output intensity map may be an intensity map of ultraviolet light that is the output of the wavelength converter.
[0120]
In the light amount control device 16C, when performing the light amount control by the third function, the light amount control is performed based on the set light amount given from the main control device 50 and the third output intensity map. ing.
[0121]
In addition to the EOM 160C, an EOM for transmittance control is provided at the output stage of the DFB semiconductor laser 160A, and the transmittance of the EOM is changed by changing the voltage applied to the EOM. It is also possible to change the energy emitted from the optical amplification unit and the wavelength conversion unit.
[0122]
As is clear from the above description, the second and third functions of the light amount control device 16C can more finely control the light amount of the output light of the light source device 16 than the first function. On the other hand, the first function can set a wider dynamic range than the second and third functions.
[0123]
Therefore, in the present embodiment, in the later-described exposure, the exposure amount is roughly adjusted by the first function of the light amount control device 16C, and the exposure amount is finely adjusted by using the second and third functions. It has become. This will be described later.
[0124]
In addition to this, the light amount control device 16C also controls the start and stop of pulse output based on an instruction from the main control device 50.
[0125]
The polarization adjusting device 16D includes an optical fiber amplifier 171._nThe optical fiber amplifier 171 is controlled by controlling the polarization characteristic of the optical component in the previous stage._nThe light emitted from the light is circularly polarized. Optical fiber amplifier 171_nIf the doped fiber has a substantially cylindrically symmetric structure and is relatively short, the optical fiber amplifier 171_nThe optical fiber amplifier 171 can also be obtained by circularly polarizing light incident on the optical fiber amplifier 171._nThe light emitted from can be circularly polarized.
[0126]
Here, the optical fiber amplifier 171_nThe optical component in the previous stage includes a relay optical fiber (not shown) for optically coupling the elements of the optical amplification unit 161 described above. As a method for controlling the polarization characteristics of such a relay optical fiber, for example, there is a method of applying anisotropic mechanical stress to the relay optical fiber, and this method is also adopted in this embodiment.
[0127]
In general, a relay optical fiber has a cylindrically symmetric refractive index profile, but when an anisotropic mechanical stress is applied, an anisotropic stress is generated in the relay optical fiber, and this stress causes anisotropy. A refractive index profile. By controlling the generation amount of such an anisotropic refractive index distribution, the polarization characteristics of the relay optical fiber can be controlled.
[0128]
Further, the amount of change in the refractive index distribution due to the stress of the relay optical fiber and the polarization characteristics of other optical components generally depend on temperature. For this reason, the polarization adjusting device 16D performs temperature control that makes the ambient temperature of the relay optical fiber or the like constant, so that the circular polarization once performed can be maintained.
[0129]
In addition, without performing the above temperature control, the polarization state of light is monitored at any position downstream of the relay optical fiber, and based on the monitoring result, the polarization characteristic of the relay optical fiber, that is, the refractive index distribution May be controlled.
[0130]
Returning to FIG. 1, the illumination optical system 12 includes a beam shaping optical system 18, a fly-eye lens system 22 as an optical integrator (homogenizer), an illumination system aperture stop plate 24, a beam splitter 26, a first relay lens 28A, a second A relay lens 28B, a fixed reticle blind 30A, a movable reticle blind 30B, a mirror M for bending an optical path, a condenser lens 32, and the like are provided.
[0131]
The beam shaping optical system 18 changes the cross-sectional shape of LB (hereinafter referred to as “laser beam”) LB generated by wavelength conversion of the wavelength conversion unit 163 of the light source device 16 to the rear of the optical path of the laser beam LB. The lens is shaped so as to be efficiently incident on the fly-eye lens system 22 provided in the lens, and is composed of, for example, a cylinder lens or a beam expander (both not shown).
[0132]
The fly-eye lens system 22 is arranged on the optical path of the laser beam LB emitted from the beam shaping optical system 18, and is a surface light source consisting of a large number of light source images to illuminate the reticle R with a uniform illuminance distribution, that is, a secondary light source. Form a light source. In this specification, the laser beam emitted from the secondary light source is also referred to as “exposure light IL”.
[0133]
An illumination system aperture stop plate 24 made of a disk-like member is disposed in the vicinity of the exit surface of the fly-eye lens system 22. The illumination system aperture stop plate 24 includes, for example, an aperture stop composed of a normal circular aperture, an aperture stop composed of a small circular aperture, an aperture stop for reducing the σ value as a coherence factor, and a ring for annular illumination. A band-shaped aperture stop, and a modified aperture stop (only two of these aperture stops are shown in FIG. 1) formed by decentering a plurality of openings for the modified light source method are arranged. . The illumination system aperture stop plate 24 is rotated by a driving device 40 such as a motor controlled by the main control device 50, so that any one of the aperture stops of the exposure light IL corresponds to the reticle pattern. It is selectively set on the optical path.
[0134]
A beam splitter 26 having a small reflectance and a large transmittance is disposed on the optical path of the exposure light IL that has exited from the illumination system aperture stop plate 24. Further, a fixed reticle blind 30A and a movable reticle blind 30B are disposed on the rear optical path. A relay optical system composed of the first relay lens 28A and the second relay lens 28B is disposed.
[0135]
The fixed reticle blind 30A is disposed on a surface slightly defocused from the conjugate surface with respect to the pattern surface of the reticle R, and a rectangular opening that defines the illumination region 42R on the reticle R is formed. In addition, a movable reticle blind 30B having an opening having a variable position and width in the scanning direction is disposed in the vicinity of the fixed reticle blind 30A, and an illumination region 42R is passed through the movable reticle blind 30B at the start and end of scanning exposure. By further limiting the above, exposure of unnecessary portions is prevented.
[0136]
On the optical path of the exposure light IL behind the second relay lens 28B constituting the relay optical system, a folding mirror M that reflects the exposure light IL that has passed through the second relay lens 28B toward the reticle R is disposed. A condenser lens 32 is disposed on the optical path of the exposure light IL behind the mirror M.
[0137]
Further, an integrator sensor 46 and a reflected light monitor 47 are arranged on one optical path bent vertically by the beam splitter 26 in the illumination optical system 12 and the other optical path, respectively. As the integrator sensor 46 and the reflected light monitor 47, an Si-based PIN photodiode having high sensitivity in the far ultraviolet region and the vacuum ultraviolet region and having a high response frequency for detecting the pulse light emission of the light source device 16 is used. ing. A semiconductor light receiving element having a GaN crystal can be used as the integrator sensor 46 and the reflected light monitor 47.
[0138]
In the above configuration, the entrance surface of the fly-eye lens system 22, the arrangement surface of the movable reticle blind 30B, and the pattern surface of the reticle R are optically conjugate with each other and formed on the exit surface side of the fly-eye lens system 22. The light source plane and the Fourier transform plane (exit pupil plane) of the projection optical system PL are optically conjugate with each other to form a Kohler illumination system.
[0139]
The operation of the illumination system 12 configured in this manner will be briefly described. The laser beam LB pulsed from the light source device 16 enters the beam shaping optical system 18, where the rear fly-eye lens system 22 is here. After the cross-sectional shape is shaped so as to efficiently enter the light, the light enters the fly-eye lens system 22. Thereby, a secondary light source is formed on the exit-side focal plane of the fly-eye lens system 22 (the pupil plane of the illumination optical system 12). The exposure light IL emitted from the secondary light source passes through one of the aperture stops on the illumination system aperture stop plate 24 and then reaches the beam splitter 26 having a high transmittance and a low reflectivity. The exposure light IL transmitted through the beam splitter 26 passes through the first relay lens 28A, passes through the rectangular opening of the fixed reticle blind 30A and the movable reticle blind 30B, passes through the second relay lens 28B, and is reflected by the mirror M. After the optical path is bent vertically downward, the rectangular illumination area 42R on the reticle R held on the reticle stage RST is illuminated with a uniform illumination distribution through the condenser lens 32.
[0140]
On the other hand, the exposure light IL reflected by the beam splitter 26 is received by the integrator sensor 46 via the condenser lens 44, and the photoelectric conversion signal of the integrator sensor 46 passes through a peak hold circuit and an A / D converter (not shown). To the main controller 50 as an output DS (digit / pulse). A correlation coefficient between the output DS of the integrator sensor 46 and the illuminance (exposure amount) of the exposure light IL on the surface of the wafer W is stored in a memory 51 as a storage device provided in the main controller 50. ing.
[0141]
Also, the reflected light beam that illuminates the illumination area 42R on the reticle R and is reflected by the pattern surface (the lower surface in FIG. 1) of the reticle passes through the condenser lens 32 and the relay optical system in the opposite direction to the front, and the beam splitter 26 And is received by the reflected light monitor 47 via the condenser lens 48. When the Z tilt stage 58 is below the projection optical system PL, the exposure light IL transmitted through the pattern surface of the reticle is the surface of the projection optical system PL and the wafer W (or the surface of a reference mark plate FM described later). The reflected light flux sequentially passes through the projection optical system PL, reticle R, condenser lens 32, and relay optical system in the reverse direction to the front, is reflected by the beam splitter 26, and is reflected by the condenser lens 48. Light is received by the monitor 47. Each optical element disposed between the beam splitter 26 and the wafer W has an antireflection film formed on the surface thereof, but the exposure light IL is slightly reflected on the surface, and the reflected light is also reflected light. Light is received by the monitor 47. The photoelectric conversion signal of the reflected light monitor 47 is supplied to the main controller 50 via a peak hold circuit and an A / D converter (not shown). In the present embodiment, the reflected light monitor 47 is mainly used for measuring the reflectance of the wafer W or the like. Note that the reflected light monitor 47 may be used for the prior measurement of the transmittance of the reticle R.
[0142]
As the fly-eye lens system 22, for example, JP-A-1-235289 (corresponding US Pat. No. 5,307,207), JP-A-7-142354 (corresponding US Pat. No. 5,534,970), etc. The disclosed double fly-eye lens system may be adopted to constitute a Kohler illumination system.
[0143]
A diffractive optical element may be used together with the fly-eye lens system 22. When such a diffractive optical element is used, the light source device 16 and the illumination optical system 12 may be connected via the diffractive optical element. That is, a diffractive optical element in which a diffractive element is formed corresponding to each fiber of the fiber bundle 173 is provided in the beam shaping optical system 18, and the laser beam output from each fiber is diffracted to enter the fly-eye lens system 22. You may make it overlap on a surface. In this example, the output end of the fiber bundle 173 may be arranged on the pupil plane of the illumination optical system. In this case, however, the intensity distribution (that is, the secondary light source) on the pupil plane is obtained by the first function (thinning). The shape and size of the image may change, and the shape and size optimal for the reticle pattern may differ. Therefore, it is desirable to superimpose the laser beam from each fiber on the pupil plane of the illumination optical system or the entrance plane of the optical integrator using the diffractive optical element described above.
[0144]
In any case, in the present embodiment, even if the distribution of the portion outputting the light of the fiber bundle 173 is changed by the first function of the light quantity control device 16C described above, the pattern surface (object surface) of the reticle R is changed. ) And the uniformity of the illuminance distribution can be sufficiently ensured on both the upper surface and the surface (image surface) of the wafer W.
[0145]
The reticle R is placed on the reticle stage RST and is sucked and held via a vacuum chuck (not shown). Reticle stage RST can be finely driven in a horizontal plane (XY plane) and is scanned within a predetermined stroke range in a scanning direction (here, the Y direction which is the horizontal direction in FIG. 1) by reticle stage driving unit 49. It has become so. The position and rotation amount of the reticle stage RST during the scanning are measured by an external laser interferometer 54R through a movable mirror 52R fixed on the reticle stage RST, and the measured value of the laser interferometer 54R is measured by the main controller. 50 is supplied.
[0146]
Note that the material used for the reticle R needs to be properly used depending on the wavelength of the exposure light IL. That is, when using exposure light with a wavelength of 193 nm, synthetic quartz can be used, but when using exposure light with a wavelength of 157 nm, it is necessary to form with fluorite, synthetic quartz doped with fluorine, or quartz. is there.
[0147]
The projection optical system PL is a double-sided telecentric reduction system, for example, and is composed of a plurality of lens elements 70a, 70b,... Having a common Z-axis direction optical axis. Further, as the projection optical system PL, one having a projection magnification β of, for example, 1/4, 1/5, 1/6, or the like is used. Therefore, as described above, when the illumination region 42R on the reticle R is illuminated by the exposure light IL, an image obtained by reducing the pattern formed on the reticle R by the projection optical system PL at the projection magnification β is the surface. The resist (photosensitive agent) is applied to the slit-shaped exposure region 42W on the wafer W and transferred.
[0148]
In the present embodiment, among the lens elements described above, a plurality of lens elements can be moved independently. For example, the uppermost lens element 70a closest to the reticle stage RST is held by a ring-shaped support member 72. The support member 72 can be expanded and contracted, for example, piezoelectric elements 74a, 74b, 74c (back of the page). The side drive element 74c is supported at three points by a not-shown) and is connected to the lens barrel 76. The drive elements 74a, 74b, and 74c can move the three peripheral points of the lens element 70a independently in the direction of the optical axis AX of the projection optical system PL. That is, the lens element 70a can be translated along the optical axis AX according to the displacement amount of the drive elements 74a, 74b, and 74c, and can be arbitrarily tilted with respect to a plane perpendicular to the optical axis AX. . The voltages applied to the drive elements 74a, 74b, and 74c are controlled by the imaging characteristic correction controller 78 based on a command from the main controller 50, whereby the displacement amounts of the drive elements 74a, 74b, and 74c are changed. To be controlled. In FIG. 1, the optical axis AX of the projection optical system PL refers to the optical axis of the lens element 70 b and other lens elements (not shown) fixed to the lens barrel portion 76.
[0149]
Further, in the present embodiment, the relationship between the vertical amount of the lens element 70a and the change amount of the magnification (or distortion) is obtained in advance by experiments, and this is stored in the memory inside the main controller 50, and at the time of correction The vertical amount of the lens element 70a is calculated from the magnification (or distortion) corrected by the main controller 50, and an instruction is given to the imaging characteristic correction controller 78 to drive the drive elements 74a, 74b, and 74c, thereby driving the magnification (or distortion). ) Correction is to be performed. The relationship between the vertical amount of the lens element 70a and the amount of change such as magnification may be an optically calculated value. In this case, an experiment for obtaining the relationship between the vertical amount of the lens element 70a and the amount of change in magnification. This process can be omitted.
[0150]
As described above, the lens element 70a closest to the reticle R can be moved, but this element 70a is selected so that the influence on the magnification and distortion characteristics is greatly controlled compared to other lens elements. Any lens element may be used to adjust the lens interval in place of the lens element 70a as long as the same conditions are satisfied.
[0151]
It should be noted that other optical characteristics such as curvature of field, astigmatism, coma, or spherical aberration can be adjusted by moving at least one lens element other than the lens element 70a. In addition, by providing a sealed chamber between specific lens elements near the center in the optical axis direction of the projection optical system PL, and adjusting the pressure of the gas in the sealed chamber by a pressure adjusting mechanism such as a bellows pump, An imaging characteristic correction mechanism that adjusts the magnification of the projection optical system PL may be provided. Alternatively, for example, an aspherical lens is used as a part of the lens elements constituting the projection optical system PL, and this is rotated. May be. In this case, so-called rhombus distortion can be corrected. Alternatively, the imaging characteristic correction mechanism may be configured by providing a plane-parallel plate in the projection optical system PL and tilting or rotating the plate.
[0152]
When laser light having a wavelength of 193 nm is used as the exposure light IL, synthetic quartz, fluorite, or the like can be used as each lens element (and the plane parallel plate) constituting the projection optical system PL. When 157 nm laser light is used, fluorite is used for all materials such as lenses used in the projection optical system PL.
[0153]
The XY stage 14 is two-dimensionally driven by the wafer stage driving unit 56 in the Y direction which is the scanning direction and in the X direction perpendicular to the Y direction (the direction perpendicular to the paper surface in FIG. 1). A wafer W is held on the Z tilt stage 58 mounted on the XY stage 14 by vacuum suction or the like via a wafer holder 61 (not shown). The Z tilt stage 58 adjusts the position (focus position) of the wafer W in the Z direction with, for example, three actuators (such as a piezo element or a voice coil motor), and the wafer W with respect to the XY plane (image plane of the projection optical system PL). It has a function of adjusting the inclination angle. The position of the XY stage 14 is measured by an external laser interferometer 54W via a movable mirror 52W fixed on the Z tilt stage 58, and the measured value of the laser interferometer 54W is supplied to the main controller 50. It has become so.
[0154]
Here, the moving mirror actually includes an X moving mirror having a reflecting surface perpendicular to the X axis and a Y moving mirror having a reflecting surface perpendicular to the Y axis. X-axis position measurement, Y-axis position measurement, and rotation (including yawing amount, pitching amount, and rolling amount) measurement are provided. In FIG. 1, these are representatively movable mirrors. 52W, shown as laser interferometer 54W.
[0155]
On the Z tilt stage 58, there is a light receiving surface in the vicinity of the wafer W and the same height as the exposure surface of the wafer W, and irradiation for detecting the amount of exposure light IL that has passed through the projection optical system PL. A quantity monitor 59 is provided. The irradiation amount monitor 59 has a rectangular housing in plan view extending in the X direction that is slightly larger than the exposure area 42W, and a slit-like opening having substantially the same shape as the exposure area 42W is formed at the center of the housing. This opening is actually formed by removing a part of the light shielding film formed on the upper surface of the light receiving glass made of synthetic quartz or the like that forms the ceiling surface of the housing. An optical sensor having a light receiving element such as an Si-based PIN photodiode is disposed directly below the opening via a lens.
[0156]
The irradiation amount monitor 59 is used for measuring the intensity of the exposure light IL irradiated to the exposure region 42W. A light amount signal corresponding to the amount of light received by the light receiving element constituting the irradiation amount monitor 59 is supplied to the main controller 50.
[0157]
The optical sensor is not necessarily provided inside the Z tilt stage 58. The optical sensor is arranged outside the Z tilt stage 58, and the illumination light beam relayed by the relay optical system is transmitted via an optical fiber or the like. Of course, it may be guided to the optical sensor.
[0158]
On the Z tilt stage 58, a reference mark plate FM used when performing reticle alignment and the like, which will be described later, is provided. The surface of the reference mark plate FM is almost the same as the surface of the wafer W. On the surface of the reference mark plate FM, reference marks such as a reticle alignment reference mark and a baseline measurement reference mark are formed.
[0159]
Although not shown in FIG. 1 from the viewpoint of avoiding complications in the drawing, the exposure apparatus 10 actually includes a reticle alignment system for performing reticle alignment.
[0160]
When aligning the reticle R, first, the main controller 50 drives the reticle stage RST and the XY stage 14 via the reticle stage drive unit 49 and the wafer stage drive unit 56, so that a reference mark is placed in the rectangular exposure region 42W. A reticle alignment reference mark on the plate FM is set, and the relative position between the reticle R and the Z tilt stage 58 is set so that the reticle mark image on the reticle R substantially overlaps the reference mark. In this state, both marks are imaged by the main controller 50 using the reticle alignment system, and the main controller 50 processes the imaging signal and X and Y directions of the projected image of the reticle mark with respect to the corresponding reference mark. Is calculated.
[0161]
Further, based on the contrast information included in the detection signal (image signal) of the projection image of the reference mark obtained as a result of the alignment of the reticle, the focus offset and the leveling offset (the focal position of the projection optical system PL, the image plane inclination, etc.) ) Is also possible.
[0162]
In the present embodiment, during the above reticle alignment, the main controller 50 also measures a baseline amount of a wafer-side off-axis alignment sensor (not shown) provided on the side surface of the projection optical system PL. That is, on the reference mark plate FM, a baseline measurement reference mark is formed with a predetermined positional relationship with respect to the reticle alignment reference mark, and the amount of positional deviation of the reticle mark is measured via the reticle alignment system. In this case, by measuring the amount of displacement of the reference mark for baseline measurement with respect to the detection center of the alignment sensor via the alignment sensor on the wafer side, the baseline amount of the alignment sensor, that is, the reticle projection position and the alignment sensor, The relative positional relationship is measured.
[0163]
Furthermore, as shown in FIG. 1, the exposure apparatus 10 of the present embodiment has a light source that is controlled to be turned on and off by the main controller 50, and has a large number of pins toward the image plane of the projection optical system PL. An irradiation optical system 60a that irradiates an image forming light beam for forming an image of a hole or a slit from an oblique direction with respect to the optical axis AX, and a light receiving optical device that receives a reflected light beam of the image forming light beam on the surface of the wafer W. An oblique incident light type multipoint focal position detection system (focus sensor) comprising a system 60b is provided. The main controller 50 controls the inclination of the reflected light beam of a parallel plate (not shown) in the light receiving optical system 60b with respect to the optical axis, thereby offsetting the focus detection system (60a, 60b) according to the focus variation of the projection optical system PL. To perform the calibration. As a result, the image plane of the projection optical system PL and the surface of the wafer W are matched within the range (width) of the focal depth within the exposure area 42W. The detailed configuration of a multipoint focal position detection system (focus sensor) similar to that of the present embodiment is disclosed in, for example, Japanese Patent Laid-Open No. Hei 6-283403.
[0164]
At the time of scanning exposure or the like, the main controller 50 sets the Z position of the Z tilt stage 58 so that the focus shift becomes zero based on a defocus signal (defocus signal) from the light receiving optical system 60b, for example, an S curve signal. By performing control through a drive system (not shown), autofocus (automatic focusing) and auto leveling are executed.
[0165]
The reason why the parallel plate is provided in the light receiving optical system 60b to give an offset to the focus detection system (60a, 60b) is that, for example, the focus also changes by moving the lens element 70a up and down for magnification correction. In addition, since the projection optical system PL absorbs the exposure light IL, the imaging characteristics change and the position of the imaging plane fluctuates. In such a case, an offset is given to the focus detection system to focus the focus detection system. This is because the position needs to match the position of the imaging plane of the projection optical system PL. For this reason, in the present embodiment, the relationship between the vertical amount of the lens element 70a and the focus change amount is also obtained in advance by experiment and stored in the memory inside the main controller 50. A calculated value may be used for the relationship between the vertical amount of the lens element 70a and the focus change amount. Further, auto leveling may not be performed in the scanning direction, but only in the non-scanning direction orthogonal to the scanning direction.
[0166]
The main controller 50 includes a so-called microcomputer (or workstation) comprising a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc. In addition to the various controls described above, for example, synchronous scanning of the reticle R and the wafer W, stepping of the wafer W, exposure timing, and the like are controlled so that the exposure operation is performed accurately. Further, in the present embodiment, the main controller 50 controls the exposure amount at the time of scanning exposure as described later, calculates the fluctuation amount of the imaging characteristics of the projection optical system PL by calculation, and calculates the calculation. Based on the result, the overall characteristics of the apparatus are controlled in addition to adjusting the imaging characteristics of the projection optical system PL via the imaging characteristics correction controller 78.
[0167]
Specifically, the main controller 50 determines the speed V of the reticle R in the + Y direction (or −Y direction) via the reticle stage RST, for example, during scanning exposure._RIn synchronism with scanning at = V, the wafer W moves through the XY stage 14 at a velocity V in the −Y direction (or + Y direction) with respect to the exposure region 42W._W= Β · V (where β is the projection magnification from the reticle R to the wafer W), based on the measurement values of the laser interferometers 54R and 54W, through the reticle stage drive unit 49 and the wafer stage drive unit 56, respectively. The positions and speeds of reticle stage RST and XY stage 14 are respectively controlled. Further, at the time of stepping, the main controller 50 controls the position of the XY stage 14 via the wafer stage drive unit 56 based on the measurement value of the laser interferometer 54W.
[0168]
Next, an exposure sequence when a reticle pattern is exposed on a predetermined number (N) of wafers W in the exposure apparatus 10 of the present embodiment will be described focusing on the control operation of the main controller 50.
[0169]
First, main controller 50 loads reticle R to be exposed onto reticle stage RST using a reticle loader (not shown).
[0170]
Next, as described above, reticle alignment is performed using a reticle alignment system, and baseline measurement is performed.
[0171]
Next, main controller 50 instructs a wafer transfer system (not shown) to replace wafer W. As a result, wafer exchange (not shown) is performed by a wafer transfer system and a wafer delivery mechanism (not shown) on the XY stage 14, and then so-called search alignment and fine alignment (such as EGA) are performed. A series of alignment steps are performed. Since the wafer exchange and wafer alignment are performed in the same manner as a known exposure apparatus, detailed description thereof is omitted here.
[0172]
Next, based on the alignment result and the shot map data, the operation of moving the wafer W to the scanning start position for exposure of each shot area on the wafer W and the above-described scanning exposure operation are repeatedly performed, A reticle pattern is transferred to a plurality of shot areas on the wafer W by a step-and-scan method. During this scanning exposure, the main controller 50 gives a command to the light quantity controller 16C while monitoring the output of the integrator sensor 46 in order to give the target integrated exposure amount determined in accordance with the exposure condition and resist sensitivity to the wafer W. give. Thereby, in the light quantity control device 16C, the exposure amount is roughly adjusted by the first function described above, and the laser beam (ultraviolet pulse light) from the light source device 16 is obtained by the second function and the third function described above. The frequency and peak power are controlled to finely adjust the exposure amount.
[0173]
The main control device 50 controls the illumination system aperture stop plate 24 via the drive device 40, and further controls the opening / closing operation of the movable reticle blind 30B in synchronization with the operation information of the stage system.
[0174]
When the exposure of the first wafer W is completed, main controller 50 instructs the wafer transfer system (not shown) to replace wafer W. As a result, wafer exchange is performed by a wafer transfer system and a wafer delivery mechanism (not shown) on the XY stage 14, and thereafter, the search alignment and fine alignment are performed on the wafer after the exchange in the same manner as described above. In this case, the irradiation fluctuation of the imaging characteristics (including the fluctuation of the focus) of the projection optical system PL from the start of exposure of the first wafer W by the main controller 50 is caused by the integrator sensor 46 and the reflected light monitor 47. A command value that is obtained based on the measured value and corrects this irradiation variation is given to the imaging characteristic correction controller 78 and an offset is given to the light receiving optical system 60b. Further, main controller 50 obtains the atmospheric pressure fluctuation amount of the imaging characteristic of projection optical system PL based on the measurement value of atmospheric pressure sensor 77, and gives a command value for correcting this irradiation fluctuation to the imaging characteristic. An offset is given to the light receiving optical system 60b as well as to the correction controller 78.
[0175]
Similarly to the above, the reticle pattern is transferred to the plurality of shot areas on the wafer W by the step-and-scan method.
[0176]
In this case, the rough adjustment of the exposure amount (light quantity) described above may be performed with test light emission before the actual exposure and reliably controlled with an accuracy of 1% or less with respect to the exposure amount setting value.
[0177]
The dynamic range of the rough adjustment of the exposure amount in the present embodiment can be set within a range of 1 to 1/128, but the dynamic range normally required is typically about 1 to 1/7. The number of channels (number of optical fibers) whose light output should be turned on may be controlled between 128 and 18. As described above, in the present embodiment, the exposure amount control by individually turning on / off the light output of each channel can accurately perform the rough adjustment of the exposure amount in accordance with the difference in the resist sensitivity for each wafer.
[0178]
Further, the light amount control by the second and third functions by the light amount control device 16C described above has a feature that the control speed is high and the control accuracy is high. Therefore, the following control request is required for the current exposure apparatus. Can be reliably satisfied.
[0179]
Therefore, in order to control the exposure amount, it is sufficient for the light amount control device 16C to perform at least one of the light amount control by the second and third functions.
[0180]
Also in the exposure apparatus 10 of the present embodiment, it is of course possible to control the exposure amount by combining either the light amount control by the second or third function of the light amount control device 16C and the scan speed. .
[0181]
The exposure condition of the wafer W is changed according to the reticle pattern to be transferred onto the wafer W. For example, the intensity distribution of illumination light on the pupil plane of the illumination optical system (that is, the shape and size of the secondary light source) ) Or an optical filter that shields a circular area centered on the optical axis on substantially the pupil plane of the projection optical system PL. The illuminance on the wafer W changes due to the change in the exposure condition, and this also occurs due to the change in the reticle pattern. This is due to the difference in the occupied area of the light shielding part (or transmission part) of the pattern. Therefore, it is desirable to control at least one of the above-described frequency and peak power so that an appropriate exposure amount is given to the wafer (resist) when the illuminance changes by changing the exposure conditions and / or the reticle pattern. . At this time, the scanning speed of the reticle and the wafer may be adjusted in addition to at least one of the frequency and the peak power.
[0182]
As described above, according to the light source device according to the present embodiment, the polarization adjusting device 16D includes the optical fiber amplifier 171._nThe polarization state of the light beams emitted from each is aligned with circularly polarized light, and all of these light beams are converted into linearly polarized light in the same direction by one quarter wavelength plate 162 and emitted. Therefore, by appropriately setting the optical axis direction of the ¼ wavelength plate, the wavelength conversion unit 163 at the subsequent stage can efficiently generate the wavelength-converted light. Further, since the polarization direction conversion device has a very simple configuration of one quarter wavelength plate 162, the light source device 16 as a whole can be reduced in size.
[0183]
Further, according to the light source device 16 according to the present embodiment, the optical fiber amplifier 171 is used._nSince the plurality of light beams emitted from the light are linearly polarized in the same direction, the light emitted from the quarter-wave plate 162 is converted into a plurality of linearly polarized light beams having high intensity and the same polarization direction. Obtainable. As a result, it is possible to increase the amount of emitted light as the light source device 16.
[0184]
Further, according to the light source device 16 according to the present embodiment, the optical fiber amplifier 171 is used._nSince each of the plurality of light beams incident on the pulse light train is a pulse light train, the light amount of the emitted light as the light source device 16 can be accurately controlled by adjusting the repetition period and the pulse height of the light pulse in each pulse light train. it can.
[0185]
Further, according to the light source device 16 according to the present embodiment, the optical fiber amplifier 171 is used._nEach of the plurality of light beams incident on the optical fiber amplifier 171_nBefore entering the optical fiber amplifier 167_nThe multi-stage optical fiber amplifier 167._n171_nAs a result of the multistage light amplification effect of the light source device 16, the amount of emitted light as the light source device 16 can be increased.
[0186]
Further, according to the light source device 16 according to the present embodiment, the optical fiber amplifier 171 is used._nSince the polarization adjustment is performed by applying anisotropic stress to the relay optical fiber, which is an optical component arranged on the upstream side, to control the polarization characteristics, the optical fiber amplifier 171_nEven if the doped fiber is not suitable for polarization adjustment due to application of stress or the like, the polarization of a plurality of light beams incident on the quarter-wave plate 162 without adversely affecting the performance and function of the light source device 16. The state can be aligned with circularly polarized light.
[0187]
Further, according to the light source device 16 according to the present embodiment, the optical fiber amplifier 171 is used._nSince the doped fibers are bundled almost in parallel, the occupied space can be reduced and the light receiving area of the quarter-wave plate can be reduced, so that the light source device 16 can be downsized.
[0188]
Further, according to the light source device 16 according to the present embodiment, the optical fiber amplifier 171 is used._nIs emitted in the infrared region (wavelength = 1547 nm), and the light emitted from the wavelength converter 163 is converted into ultraviolet light (wavelength = 193.4 nm), so that a fine pattern can be transferred. Suitable ultraviolet light can be generated efficiently.
[0189]
Since the exposure apparatus 10 according to the present embodiment uses the light source device 16 that efficiently generates ultraviolet light suitable for transferring a fine pattern, the pattern can be efficiently transferred to the wafer W. .
[0190]
In the above embodiment, the polarization adjusting device 16D is the optical fiber amplifier 171._nIs adjusted to circularly polarized light, but if the polarization adjustment is limited to elliptic polarization similar to each other, instead of the quarter wave plate 162, a half wave plate that rotates the polarization plane, By using a combination of the half-wave plate and a quarter-wave plate optically connected in series, an optical fiber amplifier 171 is used._nCan be converted into linearly polarized light having the same polarization direction. Here, in the serial connection of the half-wave plate and the quarter-wave plate, either may be arranged on the upstream side.
[0191]
In the above embodiment, the light incident on the quarter-wave plate 162 is the optical fiber amplifier 171._nHowever, a plurality of light beams emitted from a plurality of optical waveguide optical fibers may be incident on the quarter-wave plate 162.
[0192]
In the above-described embodiment, the case where the optical amplifying unit 161 has 128 channels of optical paths has been described. However, the number of optical paths may be arbitrary, and a product to which the light source device according to the present invention is applied, for example, an exposure apparatus. The number should be determined according to the required specifications (illuminance on the wafer) and optical performance, that is, the transmittance of the illumination optical system and projection optical system, the conversion efficiency of the wavelength converter, and the output of each optical path. That's fine. Even in such a case, the above-described control of the light amount and the exposure amount by the frequency control of the pulsed light output from the light modulation device and the peak power control can be suitably applied.
[0193]
Furthermore, in the above embodiment, the wavelength of the ultraviolet light is set to be almost the same as that of the ArF excimer laser, but the setting wavelength may be arbitrary, and the oscillation wavelength of the laser light source 160A or What is necessary is just to determine the structure of the wavelength conversion part 163, the magnification of a harmonic, etc. FIG. As an example, the set wavelength may be determined according to the design rules (line width, pitch, etc.) of the pattern to be transferred onto the wafer. Further, in the determination, the above-described exposure conditions and reticle types are used. (Whether it is a phase shift type) or the like may be considered.
[0194]
In the above embodiment, in order to control the oscillation wavelength of the laser light source 160A, the laser light is monitored by the beam monitor mechanism 164 immediately after the laser light source 160A. However, the present invention is not limited to this. For example, in FIG. As indicated by a dotted line, the light beam may be branched in the wavelength conversion unit 163 (or behind the wavelength conversion unit 163) and monitored by a beam monitor mechanism 183 similar to the beam monitor mechanism 164. Then, based on the monitor result by the beam monitor mechanism 183, it is detected whether or not wavelength conversion is performed accurately, and the main controller 50 feedback-controls the laser controller 16B based on the detection result. May be. Of course, the oscillation wavelength control of the laser light source 160A may be performed using the monitoring results of both beam monitoring mechanisms.
[0195]
In the above embodiment, the fly-eye lens system 22 is used as an optical integrator (homogenizer), but a rod integrator may be used instead. In an illumination optical system using a rod integrator, the rod integrator is arranged so that its exit surface is almost conjugate with the pattern surface of the reticle R. A blind 30A and a movable reticle blind 30B may be arranged.
[0196]
Although not particularly described in the above embodiment, in the case of an apparatus that performs exposure with an exposure wavelength of 193 nm or less as in the present embodiment, clean air that has passed through a chemical filter or a part that passes through a chemical filter is used in the light beam passage portion. , Dry air, N₂A treatment such as filling or flowing a gas or an inert gas such as helium, argon, or krypton, or evacuating the light beam passage portion is required.
[0197]
The exposure apparatus of the above embodiment is manufactured by assembling various subsystems including the respective constituent elements recited in the claims of the present application so as to maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. Is done. In order to ensure these various accuracies, before and after assembly, various optical systems are adjusted to achieve optical accuracy, various mechanical systems are adjusted to achieve mechanical accuracy, and various electrical systems are Adjustments are made to achieve electrical accuracy. The assembly process from the various subsystems to the exposure apparatus includes mechanical connection, electrical circuit wiring connection, pneumatic circuit piping connection and the like between the various subsystems. Needless to say, there is an assembly process for each subsystem before the assembly process from the various subsystems to the exposure apparatus. When the assembly process of the various subsystems to the exposure apparatus is completed, comprehensive adjustment is performed to ensure various accuracies as the entire exposure apparatus. The exposure apparatus is preferably manufactured in a clean room where the temperature, cleanliness, etc. are controlled.
[0198]
In the above embodiment, the case where the light source device according to the present invention is applied to a step-and-scan type scanning exposure apparatus has been described. However, an apparatus other than the exposure apparatus, for example, a circuit formed on a wafer The light source device according to the present invention can also be applied to a laser repair device used to cut a part of a pattern (such as a fuse). The light source device according to the present invention can also be applied to an inspection device using visible light or infrared light. In this case, it is not necessary to incorporate the wavelength conversion unit described above into the light source device. That is, the present invention is effective not only for an ultraviolet laser device but also for a laser device that generates a fundamental wave in the visible region or the infrared region and has no wavelength conversion unit. The present invention is not limited to the step-and-scan type scanning exposure apparatus, but can be suitably applied to a stationary exposure type, for example, a step-and-repeat type exposure apparatus (stepper or the like). Furthermore, the present invention can be applied to a step-and-stitch type exposure apparatus, a mirror projection aligner, and the like.
[0199]
Note that the projection optical system and the illumination optical system shown in the above embodiment are merely examples, and the present invention is of course not limited thereto. For example, the projection optical system is not limited to a refractive optical system, and a reflective system composed only of reflective optical elements, or a catadioptric system having a reflective optical element and a refractive optical element (catadioptric system) may be employed. In an exposure apparatus that uses vacuum ultraviolet light (VUV light) having a wavelength of about 200 nm or less, a catadioptric system may be used as the projection optical system. Examples of the catadioptric projection optical system include a catadioptric system having a beam splitter and a concave mirror as a reflective optical element, as disclosed in, for example, Japanese Patent Application Laid-Open Nos. 8-171054 and 10-20195, and the like. A catadioptric system having a concave mirror or the like can be used without using a beam splitter as a reflective optical element, as disclosed in Kaihei 8-334695 and JP-A-10-3039.
[0200]
In addition, a plurality of refractive optical elements and two mirrors (a main mirror that is a concave mirror, a refractive element, or a plane-parallel plate) disclosed in US Pat. No. 5,488,229 and JP-A-10-104513 A secondary mirror, which is a back mirror having a reflecting surface formed on the opposite side of the incident surface, and an intermediate image of the reticle pattern formed by the plurality of refractive optical elements, A catadioptric system that re-images the wafer by a mirror may be used. In this catadioptric system, a primary mirror and a secondary mirror are arranged after a plurality of refractive optical elements, and illumination light is reflected in the order of the secondary mirror and primary mirror through a part of the primary mirror. It reaches the wafer through the part.
[0201]
Of course, it is used not only for the exposure apparatus used for the manufacture of semiconductor elements, but also for the manufacture of displays including liquid crystal display elements, etc., used for the manufacture of exposure apparatuses for transferring device patterns onto glass plates, and the production of thin film magnetic heads. The present invention can also be applied to an exposure apparatus that transfers a device pattern onto a ceramic wafer and an exposure apparatus that is used for manufacturing an image pickup device (CCD or the like).
[0202]
【The invention's effect】
As described above in detail, according to the light source device of the present invention, after the polarization adjusting device aligns the polarization states of the plurality of light beams emitted from the plurality of optical fibers, the polarization direction changing device is configured to include the plurality of optical fibers. Are converted into a plurality of linearly polarized light beams having the same polarization direction, a plurality of light beams having the same polarization direction can be obtained with a simple configuration.
[0203]
Further, according to the exposure apparatus of the present invention, the light source apparatus of the present invention that efficiently generates ultraviolet light suitable for transfer of a fine pattern is used as an exposure beam generating apparatus. Can be transferred to the substrate.
[Brief description of the drawings]
FIG. 1 is a drawing schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing an internal configuration of the light source device of FIG. 1 together with a main controller.
3 is a diagram schematically showing a configuration of an optical amplifying unit in FIG. 2. FIG.
FIG. 4 is a view showing a cross section of a bundle-fiber formed by bundling output ends of a final-stage fiber amplifier constituting an optical amplifier.
5 is a diagram schematically showing a fiber amplifier and its peripheral part constituting the optical amplifying part of FIG. 2 together with a part of a wavelength converting part. FIG.
6 is a diagram illustrating a configuration of a wavelength conversion unit in FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Exposure apparatus, 16 ... Light source apparatus, 16D ... Polarization adjustment apparatus, 162 ... 1/4 wavelength plate (polarization direction conversion apparatus), 163 ... Wavelength conversion part (wavelength conversion apparatus), W ... Wafer (substrate).

Claims (12)

With a plurality of optical fibers;
A polarization adjusting device for aligning the polarization states of a plurality of light beams having the same wavelength via the plurality of optical fibers;
A polarization direction conversion device that converts all light beams through the plurality of optical fibers into a plurality of linearly polarized light beams having the same polarization direction ;
A light amount control device that controls the amount of light emitted from the plurality of optical fibers by individually turning on and off the light output from the plurality of optical fibers, and a light source device comprising:
Each of the plurality of optical fibers is an optical fiber in which the amplification target light is guided, which constitutes an optical fiber amplifier that uses a plurality of light beams incident on the plurality of optical fibers as amplification target light. Light source device. The polarization adjusting device is configured so that the polarization state of each of the plurality of light beams through the optical fibers is substantially circularly polarized,
The light source device according to claim 1, wherein the polarization direction conversion device includes a ¼ wavelength plate. The optical fiber has a substantially cylindrically symmetric structure;
The light source device according to claim 2, wherein the polarization adjusting device substantially circularly polarizes a polarization state of each of the plurality of light beams incident on the optical fibers. The polarization adjusting device has substantially the same elliptical polarization as the polarization state of each of the plurality of light beams through the optical fibers,
2. The polarization direction conversion device according to claim 1, comprising: a half-wave plate that rotates a plane of polarization; and a quarter-wave plate that is optically connected in series with the half-wave plate. The light source device described. Wherein the plurality of each of the plurality of light beams incident on the optical fiber to a light source device according to any one of claims 1 to 4, characterized in that a pulsed light train. Wherein the plurality of each of the plurality of light beams incident to the optical fiber, before being incident to the plurality of optical fibers, according to claim 1 to 5, characterized in that the light beam is amplified by one or more stages of the optical fiber amplifier The light source device according to any one of the above. The polarization adjustment device according to any one of claims 1 to 6, wherein the performing control to the polarization adjusting the optical properties of the arranged optical components upstream of the plurality of optical fibers Light source device. It said plurality of optical fibers, a light source device according to any one of claims 1 to 7, characterized in that are bundled substantially parallel. Wherein the light flux emitted from the polarization direction converter, by passing through at least one of the nonlinear optical crystal, to any one of claims 1-8, characterized by further comprising a wavelength converter for performing a wavelength conversion The light source device described. The light emitted from the plurality of optical fibers having any wavelength in the infrared region and the visible region, the light emitted from the wavelength conversion device in claim 9, characterized in that it has a wavelength in the ultraviolet range The light source device described. The light source device according to claim 10 , wherein light emitted from the plurality of optical fibers has a wavelength near 1547 nm, and light emitted from the wavelength conversion device has a wavelength near 193.4 nm. . In an exposure apparatus for transferring a predetermined pattern to a substrate by irradiating the substrate with an exposure beam,
An exposure apparatus comprising the light source device according to claim 10 or 11 as the exposure beam generator.

Images