JP2005005407A - Light source device, aligner, and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source device which can increase the frequency of a pulsed light easily. <P>SOLUTION: Laser beams LA, LB which are subjected to pulse luminescence by two sets of pulsed laser light sources 2A, 2B are lead to two fly eye lenses 8A, 8B of prestage through beam shaping optical systems 4A, 4B etc., respectively. Laser beams output from the fly eye lenses 8A, 8B are so cast that the beams are superimposed all over the plane of incidence of a latter fly eye lens 10. A reticle R is illuminated with a pulsed exposure light IL compounded by the fly eye lens 10 through blinds 14A, 14B and main condenser lens 16, etc. The pattern of the reticle R is projected on a wafer W through a projection optical system PL. Alternative luminescence of the pulsed laser optical sources 2A, 2B is carried out, and pulse exposure light IL of double frequency of the laser beams LA, LB is obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light source device using a pulse laser light source and a control method thereof, and is used in a lithography process for manufacturing various devices such as a semiconductor element, an imaging element (CCD, etc.), a liquid crystal display element, or a thin film magnetic head. It is suitable for use in an exposure light source device of an exposure apparatus.
[0002]
[Prior art]
For example, when manufacturing a semiconductor element, a batch exposure type or scanning used to transfer a reticle pattern as a mask to each shot region on a wafer (or glass plate or the like) coated with a photoresist as a substrate. In the exposure type exposure apparatus, the exposure light is gradually shortened in wavelength in order to increase the resolution. Recently, KrF excimer laser (wavelength 248 nm) is mainly used as exposure light, and ArF excimer laser (wavelength 193 nm) is also being used. Also, F with a wavelength of 157 nm ₂ The use of lasers is also being considered. Currently, all of the light sources that can be used in the wavelength region of about 300 nm or less are pulsed laser light sources.
[0003]
Further, in an exposure apparatus, there is a demand for improvement in throughput (number of wafers processed per unit time) as well as improvement in resolution. Therefore, as a method of shortening the exposure time by using a pulsed laser light source, a method of increasing each pulse energy and a method of increasing the frequency (oscillation frequency) of pulsed light emission can be considered. As a technique that substantially increases the pulse energy of the former, a light source that simultaneously emits multiple excimer laser light sources in order to reduce speckle patterns generated by mutual interference of laser light An apparatus has been proposed (see, for example, Patent Document 1). Further, in EUV lithography using, for example, EUV light (Extreme Ultraviolet Light) having a wavelength of about 5 to 50 nm as an exposure beam, laser light from a plurality of laser plasma light sources is used as an illumination optical system in order to obtain an exposure beam having a practical intensity. A light source device synthesized in the vicinity of the exit pupil has also been proposed (see, for example, Patent Document 2).
[0004]
However, in this method of increasing the pulse energy, high-energy laser light passes through the optical elements in the illumination optical system and projection optical system of the exposure apparatus in a very short time, and these optical elements are transmitted. There is a risk of causing an increase in the fluctuation of the reflectance and the reflectance. For this reason, conventionally, a single laser light source has been used to meet the demand for improved throughput mainly by increasing the frequency of pulse emission.
[0005]
[Patent Document 1]
JP 61-160776 A
[Patent Document 2]
JP 2001-68410 A
[0006]
[Problems to be solved by the invention]
As described above, conventionally, development for increasing the frequency (oscillation frequency) of pulse emission of a laser light source as an exposure light source has been mainly performed. However, when the oscillation frequency is further increased, the currently used KrF or ArF excimer laser has a problem that the load of the laser light source becomes too large.
[0007]
In other words, since the excimer laser uses gas as the laser medium, simply increasing the frequency of the laser light source alone requires increasing the flow rate of the stirring fan in the discharge chamber, leading to an increase in size and weight of the laser light source. I will. Furthermore, the energy required for the exposure light source, the spectrum, and the stability of the shape (profile) of each pulsed light (hereinafter referred to as “optical quality”) are becoming stricter year by year. There is also a problem that the optical quality is disturbed by standing waves called acoustic waves in the discharge chamber. Therefore, in the excimer laser currently used, it is necessary to devise a special damping mechanism or the like in the discharge chamber for damping the acoustic wave. Further, as the laser light source becomes larger, for example, it is necessary to increase the capacity per unit of piping for cooling water and heat exhaust treatment prepared at the semiconductor device manufacturing factory side, and the factory equipment is newly established or renovated. There is a need.
[0008]
Moreover, since the increase in the size of the laser light source causes an increase in the cost of the exposure light source, a greater investment in equipment is required. On the other hand, in order to reduce the manufacturing cost at the semiconductor element manufacturing factory, it is necessary to push the exposure apparatus operating rate to the limit level. However, since consumable parts in the laser light source need to be replaced at a certain frequency, the time during which the exposure apparatus cannot be operated (downtime) cannot be reduced to zero when one laser light source is used.
[0009]
In addition, since the excimer laser has an oscillation frequency dependency with respect to the above-described optical quality, the region of the usable oscillation frequency is limited when securing high optical quality. Therefore, if the frequency of the laser light source is increased, the entire laser light source will be optimized for operating conditions at a high frequency, so the optical quality will not be maintained when operating at a low oscillation frequency, and the usable range Will become narrower. In the exposure apparatus, the illuminance on the wafer surface is adjusted when exposing a highly sensitive resist. In the case of an excimer laser, the variable range of the pulse energy is narrow in a short period such as when the pulsed light is not emitted (one pulse emission cycle), so the illuminance adjustment relies exclusively on the variable frequency.
[0010]
For this reason, raising the minimum frequency by increasing the frequency results in the use of a mechanism such as an attenuator in the transmission optical system for the purpose of reducing the illuminance, which causes a problem that the utilization efficiency of light energy is lowered.
In view of the above, an object of the present invention is to provide a light source technique capable of easily increasing the frequency of pulsed light and an exposure technique using the same.
It is another object of the present invention to provide a light source technique having a wide variable range of the frequency of pulsed light and an exposure technique using the same.
[0011]
[Means for Solving the Problems]
The light source device according to the present invention combines a plurality of pulse laser light sources (2A, 2B) that emit laser light in a pulsed manner and laser light emitted from the plurality of pulse laser light sources into pulse light (IL) that passes through a common optical path. And a control system (32) for controlling the plurality of pulse laser light sources and alternately emitting the laser light from the plurality of pulse laser light sources. .
[0012]
According to the present invention, when the number of the plurality of pulse laser light sources is N (N is an integer of 2 or more), the frequency of the pulse light synthesized by the synthesis optical system is substantially equal to the pulse of each pulse laser light source. N times the frequency of light emission. Therefore, the frequency of pulse emission can be easily increased without increasing the size of each pulse laser light source.
In this case, for example, the control system causes one pulse laser light source among the plurality of pulse laser light sources to emit light at a substantially constant output, and controls the pulse light emission timing of the other pulse laser light sources to an arbitrary timing. To do. As described above, the control method using one pulse laser light source as a master is easy to control and can improve the stability of the output of the combined pulsed light.
[0013]
Further, it further includes a photoelectric sensor (18) for detecting the amount of pulsed light synthesized by the synthesis optical system, and the control system is a pulse emitted from the plurality of pulse laser light sources and passed through the synthesis optical system. It is desirable to control the output at the time of pulse emission of each of the plurality of pulse laser light sources based on the detection result of the light amount by the photoelectric sensor. In this way, by using the detection result of the light amount of the combined pulsed light, the light amount at the stage of actually using the pulsed light can be controlled with high accuracy. Further, when the plurality of pulse laser light sources are, for example, A and B, the detection results of the light amounts of the pulse lights emitted from the pulse laser light sources A and B among the combined pulse lights are respectively converted into the original pulse laser light source A and By feeding back to the output of B, the outputs of the pulse laser light sources A and B can be controlled with high accuracy.
[0014]
Further, the synthesis optical system includes a first optical integrator (8A, 8B) that receives the laser beams emitted from the plurality of pulsed laser light sources in different regions and guides them to a common incident surface (10b); It is desirable to have a second optical integrator (10) that forms a plurality of light source images from a plurality of laser beams incident on the common incident surface. In this way, by combining the pulsed light via the first and second optical integrators, the influence of the optical axis shift can be reduced and the light loss can be reduced.
[0015]
Also, as an example, the pulse emission frequency of the plurality of pulse laser light sources is 1.0 kHz to 4 kHz, and the control system causes the plurality of pulse laser light sources to alternately emit pulses at substantially equal time intervals. Is desirable. Thereby, when the light source device is applied to an exposure apparatus, exposure amount control becomes easy.
Further, the number of the plurality of pulse laser light sources is N (N is an integer of 2 or more), the minimum pulse emission frequency of the plurality of pulse laser light sources is Rmin, and is necessary at the stage after being synthesized by the synthesis optical system. Assuming that the frequency of simple pulse emission is f, and the frequency f is smaller than N · Rmin, the control system obtains α satisfying the following formula as an example (α is an integer not less than 1 and not more than (N−1)). The α pulse laser light sources among the N pulse laser light sources stop emitting light.
[0016]
(N−α) · Rmin <f <N · Rmin (1)
In this way, by emitting only some of the pulsed laser light sources according to the application, even if the variable range of the pulsed light emission frequency of each individual pulsed laser light source is narrow, the frequency of the combined pulsed light can be easily adjusted over a wide range. Can be controlled.
An exposure apparatus according to the present invention is an exposure apparatus that illuminates a first object (R) with an exposure beam from an exposure light source apparatus and exposes the second object (W) through the first object with the exposure beam. The light source device of the present invention is used as the exposure light source device.
[0017]
By applying the light source device of the present invention, the frequency of the pulsed light as the exposure beam can be easily increased, so that the throughput of the exposure process can be increased without newly setting up factory facilities.
In this case, the laser beam may be emitted from some of the plurality of pulsed laser light sources. As a result, it is possible to easily cope with the case of using a highly sensitive photosensitive material, and it is possible to exchange or maintain other pulse laser light sources without stopping the operation of the exposure apparatus.
[0018]
Also, a control method of a light source device according to the present invention is a control method of a light source device having a plurality of pulse laser light sources (2A, 2B) that emit laser light in pulses, and controls the plurality of pulse laser light sources. The laser light is emitted from a plurality of pulse laser light sources alternately, and the laser light emitted from the plurality of pulse laser light sources is combined with pulse light (IL) passing through a common optical path.
[0019]
According to the present invention, the frequency of pulse emission can be easily increased without increasing the size of individual pulse laser light sources.
In this case, for example, one pulse laser light source among the plurality of pulse laser light sources emits light with a substantially constant output, and the pulse light emission timings of the other pulse laser light sources are controlled to arbitrary timings. This facilitates the light emission control of the plurality of pulse laser light sources and improves the output stability.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an exemplary embodiment of the present invention will be described with reference to the drawings. In this example, the present invention is applied to generate an exposure beam for a scanning exposure type projection exposure apparatus having a step-and-scan method.
FIG. 1 shows a schematic configuration of the projection exposure apparatus of this example. In FIG. 1, an ArF excimer laser light source (wavelength 193 nm) is used as an exposure light source, and the pulse emission frequency (oscillation frequency) is 1.0 kHz to 4 kHz. About two pulse laser light sources 2A and 2B are used. Each exposure light source includes a KrF excimer laser light source (wavelength 248 nm), F ₂ Laser light source (wavelength 157 nm), Kr ₂ Laser light source (wavelength 146 nm), Ar ₂ An ultraviolet pulsed laser light source such as a laser light source (wavelength 126 nm) can also be used.
[0021]
The first laser beam LA having an elongated rectangular shape with a cross-sectional shape of 12 mm in length and about 2 mm in width, which is pulsed from the first pulse laser light source 2A during exposure, is reflected upward by the mirror 3A for bending the optical path and then cylindrical. After passing through the beam shaping optical system 4A including the lens, the cross-sectional shape is converted into a rectangle closer to a square, for example, 18 mm long and 5 mm wide. The laser light LA emitted from the beam shaping optical system 4A is converted into a first optical integrator (a homogenizer or a homogenizer) as a parallel light beam whose cross-sectional shape is enlarged via the first lens 5A, the mirror 6A, and the second lens 7A. ) As the first fly-eye lens (fly-eye integrator) 8A. The fly-eye lens 8A is an array in which a large number of lens elements 8Aa (see FIG. 2) having a substantially square cross-sectional shape with a side width of about several millimeters are arranged in close contact vertically and horizontally. The laser light LA from a large number of light source images (primary images) formed on the focal plane on the exit side of the first fly-eye lens 8A is used as a second optical integrator (a homogenizer or a homogenizer). The incident surface 10b of the fly-eye lens 10 is illuminated obliquely with a substantially uniform illuminance distribution as a whole.
[0022]
In parallel with members from the first pulse laser light source 2A to the first fly-eye lens 8A in the previous stage, members from the second pulse laser light source 2B having the same configuration as those to the second fly-eye lens 8B in the previous stage, respectively. Is arranged. Then, the second laser beam LB having a long and narrow rectangular cross-sectional shape emitted from the second pulse laser light source 2B is reflected upward by the mirror 3B, and then the beam shaping optical system 4B, the first lens 5B, and the mirror. 6B and the second lens 7B enter the second fly-eye lens 8B at the preceding stage as the first optical integrator as an enlarged parallel light beam having a rectangular cross-section that is closer to a square. Laser light LB from a large number of light source images (primary images) formed on the focal plane on the exit side of the second fly-eye lens 8B is incident on the incident surface 10b of the fly-eye lens 10 at the subsequent stage to the first laser light. Illuminates with an almost uniform illumination distribution obliquely as a whole in symmetry with LA. From a large number of light source images 33 (secondary images, see FIG. 2) formed on the focal plane on the exit side of the fly-eye lens 10, the laser beams LA and LB are combined as pulsed light that passes through a common optical path. Pulse exposure light IL (exposure beam) is emitted.
[0023]
The fly-eye lens 10 at the rear stage is an array in which a large number of lens elements 10a (see FIG. 2) having a rectangular cross-section with an aspect ratio of about 1: 3 are in close contact with each other vertically and horizontally. The overall outer shape of the fly-eye lens 10 (the shape of the incident surface 10b) is substantially similar to the cross-sectional shape of each lens element constituting the front-stage fly-eye lenses 8A and 8B. The front fly-eye lenses 8A and 8B are arranged along the longitudinal direction of the lens elements constituting the rear fly-eye lens 10. In FIG. 1, the fly-eye lenses 8A and 8B in the front stage are represented as lens elements arranged in 6 rows × 6 columns, and the fly-eye lens 10 in the rear stage is represented as lens elements arranged in 3 rows × 6 columns. These are shown for convenience of explanation. That is, the number and arrangement of lens elements constituting the fly-eye lenses 8A, 8B, and 10 are arbitrary. In this example, a combining optical system is constituted by the fly eye lenses 8A and 8B at the front stage and the fly eye lens 10 at the rear stage. Further, pulse laser light sources 2A and 2B, mirrors 3A and 3B, beam shaping optical systems 4A and 4B, first lenses 5A and 5B, mirrors 6A and 6B, second lenses 7A and 7B, front-stage fly-eye lenses 8A and 8B, And the light source device (or exposure light source device) is comprised from the fly eye lens 10 of the back | latter stage.
[0024]
Illumination for determining illumination conditions by setting the exposure light quantity distribution to a circular shape, a plurality of eccentric regions, or an annular shape on the exit-side focal plane (pupil surface of the illumination optical system) of the fly eye lens 10 at the subsequent stage. A system aperture stop (σ stop) member 11 is disposed. The illumination system aperture stop member 11 sets the aperture stop to the instructed shape under the control of the main control system 31 that controls the overall operation of the apparatus.
[0025]
FIG. 2 is an enlarged view showing an optical system from the second lenses 7A and 7B to the illumination system aperture stop member 11 in FIG. 1, and in FIG. 2, two laser beams LA and LB are respectively fly in front stage. The eye lenses 8A and 8B are incident on different regions of the first optical integrator. Further, the exit surface of the lens element 8Aa constituting the first fly-eye lens 8A at the front stage is inclined outward with respect to the fly-eye lens 10 at the rear stage. As a result, the laser light LA from the light source image formed on the exit-side focal plane of each lens element 8Aa is incident on substantially the entire entrance surface 10b of the fly eye lens 10 at the subsequent stage. In other words, the inclination angle of the exit surface of each lens element 8Aa is set to an angle at which the emitted laser light LA is incident on almost the entire entrance surface 10b.
[0026]
In contrast to the first fly-eye lens 8A, the exit surface of the lens element 8Ba constituting the second fly-eye lens 8B at the front stage is inclined outward with respect to the fly-eye lens 10 at the rear stage. As a result, the laser light LB from the light source image formed on the exit-side focal plane of each lens element 8Ba is tilted symmetrically with the laser light LA on almost the entire entrance surface 10b of the fly-eye lens 10 at the subsequent stage. Incident. That is, the laser beams LA and LB are incident on a common area of the fly-eye lens 10 as the second optical integrator. A large number of light source images 33 are formed by the laser beams LA and LB on the focal plane on the exit side of the fly-eye lens 10, and the pulsed light from these light source images 33 becomes the pulse exposure light IL.
[0027]
In this way, in the configuration in which the two laser beams LA and LB are synthesized using the front fly-eye lenses 8A and 8B and the rear fly-eye lens 10, the optical axes of the fly-eye lenses 8A and 8B and the fly-eye lens 10 Even if the positional relationship with the optical axis deviates to some extent from the designed positional relationship, there is no illuminance unevenness, and there is an advantage that the light amount loss at the stage of the pulse exposure light IL is small.
[0028]
On the other hand, as shown in FIG. 6, in the configuration in which the laser beams LA and LB from the two pulse laser light sources 2A and 2B are combined using the beam splitter 41 and the mirror 42 to obtain the pulse exposure light IL, The deviation of the optical axes of the two pulse laser light sources 2A and 2B becomes the positional deviation of the laser beams LA and LB as they are, and large illuminance unevenness is likely to occur. Further, a light amount loss of about ½ occurs in the beam splitter 41. In FIG. 6, the beam splitter 41 is a polarization beam splitter, half-wave plates 43A and 43B are arranged on the exit surfaces of the pulse laser light sources 2A and 2B, and the quarter-wave plate is placed on the optical path of the pulse exposure light IL. By disposing 44, it is possible to reduce the light loss. However, even in this case, there is a certain amount of light loss due to the rotation angle adjustment error of the wave plates 43A, 43B, and 44 and a light loss in the polarization beam splitter, and the problem of uneven illuminance due to optical axis deviation remains. ing.
[0029]
Returning to FIG. 2, in this example, the two laser beams LA and LB are superimposed and synthesized on almost the entire surface of the incident surface 10 b of the fly-eye lens 10 in the subsequent stage. Even in the case of emitting only (for example, 2A), there is an advantage that the light amount distribution of the pulse exposure light IL in the aperture stop of the illumination system aperture stop member 11 is almost uniform, and unevenness in illuminance hardly occurs.
[0030]
In FIG. 2, in order to efficiently guide the laser beams LA and LB from the fly-eye lenses 8A and 8B to the incident surface 10b of the fly-eye lens 10, respectively, the fly-eye lenses 8A and 8B and the fly-eye lens 10 Relay lenses 9A and 9B may be arranged between them. Further, in addition to the relay lenses 9A and 9B, a common relay lens for making each laser beam into a parallel light beam may be arranged in front of the incident surface 10b of the fly-eye lens 10. Further, the fly-eye lenses 8A and 8B are used as one fly-eye lens, and the laser beams from the pulse laser light sources 2A and 2B are irradiated to different regions on the incident surface of the one fly-eye lens (first optical integrator). You may do it.
[0031]
Returning to FIG. 1, the pulse exposure light IL that has passed through the aperture stop in the illumination system aperture stop member 11 passes through the beam splitter 12 and the relay lens 13 </ b> A having a low reflectivity, and then the fixed blind 14 </ b> A and the movable field stop as a fixed field stop. Are sequentially passed through the movable blind 14B. The movable blind 14B is disposed on a surface substantially conjugate with the pattern surface (reticle surface) of the reticle R as a mask, and the fixed blind 14A is disposed on a surface slightly defocused from the conjugate surface with the reticle surface. Yes.
[0032]
The fixed blind 14A is used to define the shape of the illumination area 19R on the reticle R. The movable blind 14B includes two pairs of blades that can move relative to each other in a direction corresponding to the scanning direction and the non-scanning direction of the reticle R, and is unnecessary at the start and end of scanning exposure for each shot area to be exposed. It is used to close the illumination area 19R in the scanning direction so that no exposure is performed. The movable blind 14B is also used to define the center and width of the illumination area 19R in the non-scanning direction as necessary. The pulse exposure light IL that has passed through the blinds 14A and 14B passes through the sub-condenser lens 13B, the optical path bending mirror 15, and the main condenser lens 16, and the illumination area 19R on the pattern area of the reticle R as a mask has uniform illuminance. Illuminate with distribution. The illumination region 19R in this example is a slit-like region (in this example, a rectangle having an aspect ratio of approximately 1: 3) elongated in the non-scanning direction orthogonal to the scanning direction of the reticle R. The cross-sectional shape of the lens element 10a (see FIG. 2) constituting the rear fly eye lens 10 is substantially similar to the illumination region 19R.
[0033]
On the other hand, the pulse exposure light reflected by the beam splitter 12 is received by the integrator sensor 18 formed of a photoelectric sensor via the condenser lens 17. A detection signal from the integrator sensor 18 (for example, a peak hold signal for each pulse light) is supplied to the exposure amount control system 32. The exposure amount control system 32 uses the detection signal and the transmittance of the optical system from the beam splitter 12 measured in advance to the wafer W as the substrate (photosensitive substrate), and the pulse energy (pulse) on the wafer W is measured. (Exposure energy per light) is indirectly calculated. Thus, the detection signal of the integrator sensor 18 and the transmittance of the optical system (the amount of energy obtained by receiving the exposure light by the integrator sensor 18 and the exposure light on the wafer stage via the projection optical system) The pulse energy on the wafer W for each pulsed light calculated from the ratio of the amount of energy obtained by receiving light) is hereinafter referred to as “pulse energy measured for each pulsed light of the pulse exposure light IL”. Or “light quantity”. The exposure amount control system 32 uses the pulse laser light source 2 </ b> A so that an appropriate exposure amount can be obtained on the wafer W based on the measured value of each pulse energy, the integrated value of the measured value, and the control information from the main control system 31. And 2B pulse light emission operation (details will be described later).
[0034]
The illumination optical system 1 includes the light source device (exposure light source device), the illumination system aperture stop member 11, the beam splitter 12, the relay lens 13A, the blinds 14A and 14B, the sub-condenser lens 13B, the mirror 15, and the main condenser lens 16. Has been. The illumination optical system 1 is covered with a subchamber (not shown) as an airtight chamber. In order to maintain a high transmittance with respect to the pulse exposure light IL, a gas that transmits the pulse exposure light IL such as nitrogen gas (or a rare gas such as helium gas) from which impurities are highly removed is contained in the sub-chamber. Purge gas).
[0035]
Under the pulse exposure light IL, the pattern in the illumination area 19R of the reticle R is projected at a projection magnification β (β is 1/4, 1/5, etc.) via a bilateral telecentric projection optical system PL. It is projected onto an exposure area 19W on one shot area SA on the coated wafer W. The exposure area 19W is a slit-like (rectangular in this example) area elongated in the non-scanning direction conjugate with the illumination area 19R with respect to the projection optical system PL. Reticle R and wafer W correspond to the first object and the second object of the present invention, respectively. The wafer W is a disk-shaped substrate having a diameter of about 200 to 300 mm, such as a semiconductor (silicon or the like) or SOI (silicon on insulator).
[0036]
The projection optical system PL of this example is a straight tube type refraction system. When the exposure wavelength is shorter, as the projection optical system PL, for example, as disclosed in Japanese Patent Application Laid-Open No. 2000-47114, a catadioptric system composed of a plurality of optical systems having optical axes intersecting each other, or for example, As disclosed in WO 00/39623 pamphlet, a plurality of refractive lenses and two concave mirrors each having an opening in the vicinity of the optical axis are arranged along one optical axis. A straight cylindrical catadioptric system or the like that is configured can also be used. In order to maintain a high transmittance for the pulse exposure light IL, a purge gas from which impurities are highly removed is also supplied into the lens barrel of the projection optical system PL. Hereinafter, in FIG. 1, the Z axis is taken in parallel to the optical axis AX of the projection optical system PL, the Y axis is taken in the scanning direction of the reticle R and the wafer W during scanning exposure in a plane perpendicular to the Z axis, and the scanning direction The description will be made by taking the X axis in the non-scanning direction orthogonal to the axis.
[0037]
First, the reticle R is sucked and held on the reticle stage 21, and the reticle stage 21 moves on the reticle base 22 in the Y direction at a constant speed, and finely moves in the X, Y, and rotational directions so as to correct the synchronization error. Then, the reticle R is scanned. The position of the reticle stage 21 in the X direction is measured by the movable mirror 20Xm and the laser interferometer 20X. The position of the reticle stage 21 in the Y direction and the rotation angle about the Z axis are a pair of retroreflectors 24Am, 24Bm and It is measured by a pair of laser interferometers 24A and 24B corresponding to these. These measurement values are supplied to the reticle stage control system 23. The reticle stage control system 23 uses a drive mechanism (not shown) such as a linear motor based on the measurement values and control information from the main control system 31. The position and speed of the reticle stage 21 are controlled. Above the periphery of the reticle R, a reticle alignment microscope (not shown) for reticle alignment is arranged.
[0038]
On the other hand, the wafer W is sucked and held on the wafer stage 25 via a wafer holder (not shown), and the wafer stage 25 moves at a constant speed in the Y direction on the wafer base 26 made of a surface plate, Step in the direction. The wafer stage 25 also includes a Z leveling mechanism that performs focusing and leveling of the wafer W based on a measurement value of the position of the wafer W in the Z direction by an auto focus sensor (not shown). The position and rotation angle of the wafer stage 25 in the X and Y directions are measured by the X-axis and Y-axis laser interferometers 27X and 27Y, and the measured values are supplied to the wafer stage drive system 28. The wafer stage drive system 28 controls the position and speed of the wafer stage 25 via a drive mechanism (not shown) such as a linear motor based on the measured value and the control information from the main control system 31.
[0039]
Further, an off-axis type alignment sensor (not shown) for detecting an alignment mark on the wafer is disposed above the wafer stage 25, and the main control system 31 determines the wafer W based on the detection result. Perform alignment. In addition, an irradiation amount monitor 29 including a photoelectric sensor for measuring the illuminance (light amount) of the pulse exposure light IL is disposed in the vicinity of the wafer W on the wafer stage 25, and the detection signal of the irradiation amount monitor 29 is exposed. It is supplied to the quantity control system 32.
[0040]
At the time of exposure, the reticle stage 21 and the wafer stage 25 are driven to synchronously scan the reticle R and one shot area on the wafer W in the Y direction while irradiating the slit-shaped illumination area 19R with the pulse exposure light IL. The operation and the operation of moving the wafer W stepwise in the X and Y directions by driving the wafer stage 25 are repeated. By this operation, the pattern image of the reticle R is exposed to each shot area on the wafer W by the step-and-scan method.
[0041]
In this example, as shown in FIG. 1, two pulse laser light sources 2A and 2B are installed in parallel. Hereinafter, an example of the pulse light emission operation of the pulse laser light sources 2A and 2B under the control of the exposure amount control system 32 will be described with reference to FIGS. In this example, the exposure control is performed with the first pulse laser light source 2A as the master (main) and the second pulse laser light source 2B as the slave (secondary).
[0042]
FIG. 4 shows an example of oscillation timings of the two pulse laser light sources 2A and 2B during normal exposure, and the horizontal axes of FIGS. 4A, 4B, 4C, and 4D indicate the elapsed time t. 4 (A), (B), (C), and (D), the vertical axis represents the pulse energy of the laser light LA emitted from the first pulse laser light source 2A of FIG. The pulse energy of the laser beam LB emitted from the pulse laser light source 2B, the pulse energy of the combined pulse exposure light IL, and the light emission trigger pulse TP for the pulse laser light sources 2A and 2B are shown.
[0043]
As shown in FIG. 4D, the exposure amount control system 32 generates a light emission trigger pulse TP composed of periodic light emission trigger pulses TPA, TPB, TPA, TPB,... In this case, if the frequency f required at the stage of the pulse exposure light IL is 4 kHz, the time interval ΔT (= 1 / f) is set to be 0.25 msec. Further, the exposure amount control system 32 supplies an odd-numbered emission trigger pulse TPA among the emission trigger pulses TP to the first pulse laser light source 2A, and the even-numbered emission trigger pulse TPB to the second pulse laser light source 2B. To supply. Thereby, the pulse laser light sources 2A and 2B alternately emit pulses at equal time intervals ΔT. That is, as shown in FIG. 4A, the first pulse laser light source 2A emits laser light LA1, LA2, LA3,... At a frequency f / 2, and the second pulse laser light source 2B As shown in FIG. 4B, the laser beams LB1, LB2, LB3,. The exposure amount control system 32 instructs the pulse laser light sources 2A and 2B on the pulse energy for each pulse emission via a control line (not shown). In order to stabilize each pulse energy, the control range of the pulse energy for each pulse emission is set within a range of about several percent with respect to a predetermined standard output.
[0044]
At this time, the pulse exposure light IL obtained by combining the two laser beams LA and LB with the fly-eye lens 10 of FIG. 1 is, as shown in FIG. 4C, the light emission trigger pulse TP of FIG. 1 and pulse energy IL1, IL2, IL3,... Of the pulse light IL1, IL2, IL3,... On the wafer W measured by the integrator sensor 18 of FIG. Is done. In the exposure amount control system 32, a pulse laser that emits the pulse energy of the pulsed light IL1, IL2, IL3,... By capturing the detection signal (for example, peak hold signal) of the integrator sensor 17 in synchronization with the light emission trigger pulse TP. The measurement is made corresponding to the light source 2A or 2B, and the measurement result is fed back to the output at the time of the next pulse emission of the pulse laser light source 2A or 2B that has emitted light. In other words, the output of the laser light LA2, LA3,... At the time of the next light emission of the first pulse laser light source 2A corresponding to the measured value of the pulse energy of the odd-numbered pulse lights IL1, IL3,. The pulse energy measurement values of the even-numbered pulse lights IL2, IL4,... In the pulse exposure light IL are fed back to the corresponding laser beams LB2, LB3,. Feedback to output.
[0045]
In this example, since the first pulse laser light source 2A is a master, the pulse energy of the pulse lights IL1, IL3, IL5,... Emitted from the first pulse laser light source 2A is always a constant target value. The exposure amount control system 32 controls the output of each pulse of the first pulse laser light source 2A. That is, even if the same output energy is instructed in the excimer laser light source, the pulse energy varies to some extent for each pulse emission, so the exposure amount control system 32 measures the pulse energy of the pulsed light IL1, IL3, IL5,. When the measured pulse energy deviates from a certain target value to a higher (or lower) value, the output at the next pulse emission in the first pulse laser light source 2A is set to be slightly lower (or higher). To do. As a result, the pulse energy of the pulsed light IL1, IL3,... Emitted from the first pulsed laser light source 2A in the pulse exposure light IL is always controlled around a constant target value.
[0046]
On the other hand, since the second pulsed laser light source 2B is a slave, the pulse energy of the pulsed light IL2, IL4,... Emitted from the second pulsed laser light source 2B is changed at each point in each shot area SA on the wafer W. The exposure is controlled so as to be performed with a predetermined integrated exposure amount. In this case, each point on the wafer W is exposed with a predetermined number of pulses of an integer M during scanning exposure.
[0047]
FIG. 5 shows a part of the slit-shaped exposure area 19W on the wafer W in FIG. 1. In FIG. 5, the width of the exposure area 19W in the scanning direction (Y direction) is D, and one of the pulse exposure light IL. Assuming that the interval at which the point 35 on the wafer W moves in the Y direction during pulsed emission is d, the integer M is a value obtained by dividing the width D by the interval d as follows.
M = D / d (2)
Further, assuming that the sensitivity (appropriate exposure amount) of the photoresist on the wafer W is E and the target value of each pulse energy of the pulse exposure light IL is p, the target value p is as follows.
[0048]
p = E / M (3)
Therefore, as an example, when the measured value of the pulse energy of the pulsed light IL3 from the first pulsed laser light source 2A in FIG. 4C is lower than the target value p by δp, for example, the second pulsed laser light source 2B The pulse energy of the pulsed light IL4 is controlled to be higher than the target value p by δp. As a result, the output of the laser beam LB from the second pulse laser light source 2B is from the target value of the measured value of the pulse energy of the previous laser beam, as indicated by arrows 36A and 36B in FIG. It is increased or decreased to cancel the error. In this way, when the pulse energy is controlled by the second pulse laser light source 2B, the integer M in the equation (2) is set to an even number (when there are N pulse laser light sources, a multiple of N). Then, the same number of pulse lights from the pulse laser light sources 2A and 2B may be irradiated at each point on the wafer W.
[0049]
As another example, an integrated value Σi of i pulse energies (i = 0, 1, 2,..., M−1) of the pulse exposure light IL is sequentially obtained using the integrator sensor 18. The next target energy pi (= p · (i + 1) −Σi) may be calculated from the integrated value Σi. In this example, the next pulse energy of the second pulse laser light source 2B can be set based on M average values (or weighted average values) of the target energy pi.
[0050]
As described above, according to this example, the oscillation frequency in each of the pulse laser light sources 2A and 2B may be 1/2 with respect to the frequency f of the pulse exposure light IL finally obtained. Specifically, when the oscillation frequency of the pulse laser light sources 2A and 2B is about 1.0 kHz to 4 kHz, pulse exposure light IL having a frequency f of about 2 to 8 kHz can be obtained. Accordingly, the frequency of the pulse exposure light IL is reduced without changing the structure of the individual pulse laser light sources 2A and 2B, and without reducing the stability (light quality) of energy, spectrum, and shape (profile) of each pulse light. Can be easily increased. As a result, since the wafer W is irradiated with twice the exposure energy per unit time, the exposure time can be shortened and the throughput of the exposure process can be doubled. Moreover, since the structure of the pulse laser light sources 2A and 2B is the same as the conventional structure, a large capacity for cooling water, heat exhaust processing, etc. is required in the semiconductor element manufacturing factory where the projection exposure apparatus of this example is installed. There is no need to newly install piping, and an increase in manufacturing cost can be suppressed. Further, according to this example, since the minimum oscillation frequency of the pulse laser light source can be reduced, there is an advantage that it is not necessary to waste energy and the life of the pulse laser light source is extended.
[0051]
In the above embodiment, the pulse energy is controlled by the slave pulse laser light source 2B, but the pulse light emission timing may be controlled by the pulse laser light source 2B. That is, in the example of FIG. 4, the pulsed light emission of the pulse laser light source 2B is performed at a constant time interval 2 · ΔT and after the constant time interval ΔT from the pulsed light emission of the pulse laser light source 2A. However, for example, when the scanning speed in the Y direction of the wafer stage 25 (wafer W) in FIG. 1 fluctuates during scanning exposure, the pulse exposure light IL is irradiated every time the wafer W moves as much as possible. As described above, the light emission timing of the second pulse laser light source 2B may be shifted. Furthermore, you may make it control both the pulse energy and light emission timing of the 2nd pulse laser light source 2B.
[0052]
In the above-described embodiment, one pulse laser light source 2A is a master (main) and the other pulse laser light source 2B is a slave (secondary). However, both pulse laser light sources 2A and 2B are treated equally, You may make it control the output and / or light emission timing of pulse laser light source 2A, 2B, respectively.
Further, the laser light source needs periodic repair (maintenance) such as replacement of consumable parts. Therefore, in the above-described embodiment, for example, when maintenance is performed on one pulse laser light source 2B in FIG. 1, exposure may be performed using only the other pulse laser light source 2A. In this case, since the frequency of the pulse exposure light IL is the same as the conventional one, it is necessary to lengthen the exposure time, but there is an advantage that the exposure process can be continued without interruption. In addition, when an abnormality occurs in one of the two pulsed laser light sources and it is necessary to replace parts, exposure is performed by causing only the other one pulsed laser light source to emit light. You can continue. In other words, the time during which the projection exposure apparatus cannot be operated due to the pulse laser light source (down time) can be made substantially zero.
[0053]
In the above embodiment, two pulse laser light sources 2A and 2B are used. However, three or more pulse laser light sources may be used in parallel. Even when three or more pulse laser light sources are used as described above, at least one of them is used as a master (main) and driven so that the output is constant, and other pulse laser light sources are used as slaves (slave). The output and / or the light emission timing may be controlled. In addition, the three or more pulse laser light sources may be equally handled.
[0054]
3 is an enlarged view showing an optical system corresponding to the optical system from the second lenses 7A and 7B to the illumination system aperture stop member 11 in FIG. 2 when three pulse laser light sources are used. In FIG. 3, in which corresponding parts are denoted by the same reference numerals, laser beams LA, LB, and LC from three pulse laser light sources (not shown) are respectively connected to the front stage fly through second lenses 7A, 7B, and 7C. The eye lenses 34A, 34B, and 34C, that is, the first optical integrator are incident on different regions. In the configuration example of FIG. 3, the center fly-eye lens 34 </ b> A is not inclined with respect to the exit surface of each lens element, as in the case of a normal fly-eye lens. On the other hand, the exit surface of the lens element constituting the lower fly-eye lens 34 </ b> C is inclined outward with respect to the rear fly-eye lens 10. In contrast to this, the exit surface of the lens element constituting the upper fly-eye lens 34 </ b> B is inclined outward with respect to the rear fly-eye lens 10. As a result, the laser beams LA from the individual lens elements of the center fly-eye lens 34A illuminate the entire incident surface of the subsequent fly-eye lens 10 (second optical integrator). Further, the laser light LC from the individual lens elements of the lower fly-eye lens 34C and the laser light LB from the individual lens elements of the upper fly-eye lens 34B are respectively transmitted to the incident surface 10b of the fly-eye lens 10 at the subsequent stage. The light is incident on the entire surface in a symmetrical manner. That is, the laser beams LA, LB, and LC are incident on a common area of the fly-eye lens 10 as the second optical integrator. A large number of light source images 33 are formed by the laser beams LA, LB, and LC on the focal plane on the emission side of the fly-eye lens 10, and pulse light from these light source images 33 becomes pulse exposure light IL.
[0055]
In this case, relay lenses 9A, 9B, and 9C may be disposed between the fly-eye lenses 34A, 34B, and 34 and the fly-eye lens 10, respectively. In addition to the relay lenses 9A, 9B, and 9C, a common relay lens for making each laser beam into a parallel light beam may be disposed in front of the incident surface of the fly-eye lens 10.
In the configuration example of FIG. 3, the frequency of the combined pulse exposure light IL can be tripled with respect to the pulse emission frequency of each laser beam LA, LB, LC, and the throughput of the exposure process is almost tripled. Can be.
[0056]
Therefore, in general, the frequency of the pulse exposure light IL can be easily increased N times by combining laser beams from N (N is an integer of 2 or more) pulse laser light sources. Also in this case, at the time of maintenance of some pulsed laser light sources, an arbitrary number of units including at least one unit are operated, and the emission timings of the operating pulsed laser light sources are controlled so as to be at regular intervals, for example. The When a plurality of pulse laser light sources are used, maintenance of the plurality of pulse laser light sources is performed at different times so that the operation of the projection exposure apparatus can be stopped and the projection exposure apparatus can be used effectively. I can do it.
[0057]
When an exposure light source device having N pulse laser light sources is used, high-frequency pulse exposure light IL can be easily obtained, and the variable range of the frequency of pulse exposure light IL can be easily widened. You can also. In other words, when exposure is performed using photoresists with various sensitivities, low-sensitivity (large appropriate exposure amount) photoresist is exposed when N pulse lasers are used as in the above embodiment. All the light sources may be sequentially pulsed alternately at, for example, equal time intervals. On the other hand, in the case of using a highly sensitive photoresist (which requires a small appropriate exposure amount), the integrated exposure energy for each shot area on the wafer W is, for example, about 1/2 or 1/3 of the usual. It can be significantly less. Thus, even in applications where the accumulated exposure energy is significantly lower than usual, it is not desirable to significantly reduce the value of each pulse energy in order to maintain the stability of the output of each pulse laser light source. Further, when each pulse laser light source has already emitted light at a minimum frequency of, for example, about 1.5 kHz, it is difficult to further reduce the oscillation frequency.
[0058]
In such an application, the number of pulse laser light sources to be oscillated among the N pulse laser light sources is reduced. At this time, if the minimum pulse emission frequency of each pulse laser light source is Rmin and the frequency of the combined pulse exposure light IL is f, the required frequency f is considerably smaller than N · Rmin. Then, a control system corresponding to the exposure amount control system 32 of FIG. 1 obtains α (α is an integer not less than 1 and not more than (N−1)) satisfying the following equation, and among the N pulse laser light sources, α Stops the light emission of the pulse laser light source.
[0059]
(N−α) · Rmin <f <N · Rmin (4)
However, the following relationship is established, and at least one pulsed laser light source emits pulses.
N-α ≧ 1 (5)
In this state, the control system sets the oscillation frequency fad of (N−α) pulse laser light sources that emit pulses to satisfy the following expression so that the frequency of the combined pulse exposure light IL becomes f. .
[0060]
(N−α) · fad = f (6)
In this way, by emitting only some of the pulsed laser light sources according to the application, even if the variable range of the pulsed light emission frequency of each individual pulsed laser light source is narrow, the frequency of the combined pulsed light can be easily adjusted over a wide range. Can be controlled.
In the above embodiment, laser beams from a plurality of pulse laser light sources having the same oscillation frequency are combined, but laser light from a plurality of pulse laser light sources having different oscillation frequencies is combined to generate pulse exposure light. You may get. For example, pulse exposure light having a frequency (f1 + f2) may be obtained by combining laser light having the oscillation frequency f1 and laser light having twice the oscillation frequency f2 (= 2 · f1).
[0061]
In the above embodiment, fly-eye lenses (fly-eye integrators) are used as the first and second optical integrators. However, at least one of these optical integrators may be a rod-type integrator or the like. An internal reflection type integrator may be used. Furthermore, in the above embodiment, a plurality of laser beams are synthesized into pulse exposure light using the first optical integrator and the second optical integrator, but instead of the first optical integrator. A diffractive optical element (DOE) that bends the optical path by diffraction may be used.
[0062]
Further, for example, in the configuration of FIG. 1, in order to adjust the pulse energy of the pulse laser light sources 2A and 2B within a predetermined range, a dimming mechanism (optical attenuator) for mechanically controlling the transmittance within the predetermined range. May be provided.
The projection exposure apparatus of the above embodiment includes an illumination optical system composed of a plurality of lenses, a projection optical system incorporated in the exposure apparatus main body, and optical adjustment, and a reticle stage and wafer stage composed of a large number of mechanical parts. Is attached to the exposure apparatus main body, wiring and piping are connected, and further comprehensive adjustment (electrical adjustment, operation check, etc.) is performed. The exposure apparatus is preferably manufactured in a clean room where the temperature, cleanliness, etc. are controlled.
[0063]
Further, when a semiconductor device is manufactured using the projection exposure apparatus of the above-described embodiment, the semiconductor device includes a step of designing a function / performance of the device, a step of manufacturing a reticle based on this step, and a silicon material. A step of forming a wafer, a step of performing alignment with the projection exposure apparatus of the above-described embodiment and exposing a reticle pattern onto the wafer, a step of forming a circuit pattern such as etching, a device assembly step (dicing process, bonding process, (Including a packaging process) and an inspection step.
[0064]
The present invention can be applied not only to a scanning exposure type projection exposure apparatus, but also to a batch exposure type projection exposure apparatus, a proximity type exposure apparatus, or a contact type exposure apparatus. Further, the use of the exposure apparatus of the present invention is not limited to the exposure apparatus for manufacturing a semiconductor device, but for example, exposure for a display apparatus such as a liquid crystal display element formed on a square glass plate or a plasma display. The present invention can also be widely applied to an exposure apparatus for manufacturing various devices such as an apparatus, an image sensor (CCD, etc.), a micromachine, a thin film magnetic head, and a DNA chip. Furthermore, the present invention can also be applied to an exposure process (exposure apparatus) when manufacturing a mask (photomask, reticle, etc.) on which mask patterns of various devices are formed using a photolithographic process.
[0065]
In addition, this invention is not limited to the above-mentioned embodiment, Of course, a various structure can be taken in the range which does not deviate from the summary of this invention.
[0066]
【The invention's effect】
According to the present invention, the frequency of pulsed light can be easily increased by synthesizing laser beams that are alternately pulsed from a plurality of pulsed laser light sources.
Moreover, the variable range of the frequency of pulsed light can be widened by emitting laser light from some pulsed laser light sources as necessary.
[0067]
Moreover, according to the exposure apparatus of the present invention, the frequency of the pulsed light can be increased, so that the throughput of the exposure process can be increased.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic configuration of a projection exposure apparatus used in an example of an embodiment of the present invention.
2 is a partially cutaway view showing an optical system from second lenses 7A and 7B to an illumination system aperture stop member 11 in FIG.
FIG. 3 is a partially cutaway view showing an optical system of a portion corresponding to FIG. 2 when three pulse laser light sources are used.
FIG. 4 is a diagram illustrating an example of pulse emission timings of two pulse laser light sources in the embodiment of the present invention.
5 is an enlarged plan view with a part cut away showing an exposure region 19W on the wafer of FIG. 1. FIG.
FIG. 6 is a diagram showing a main part in the case of combining laser beams from two pulse laser light sources using a beam splitter.
[Explanation of symbols]
R ... reticle, PL ... projection optical system, W ... wafer, IL ... pulse exposure light, 1 ... illumination optical system, 2A, 2B ... pulse laser light source, 4A, 4B ... beam shaping optical system, 8A, 8B ... fly eye lens DESCRIPTION OF SYMBOLS 10 ... Fly eye lens, 12 ... Beam splitter, 18 ... Integrator sensor, 21 ... Reticle stage, 25 ... Wafer stage, 29 ... Irradiation amount monitor, 31 ... Main control system, 32 ... Exposure amount control system

Claims (10)

A plurality of pulsed laser light sources that emit laser light in pulses;
A synthesis optical system for synthesizing laser light emitted from the plurality of pulse laser light sources into pulse light passing through a common optical path;
And a control system that controls the plurality of pulse laser light sources and alternately emits the laser light from the plurality of pulse laser light sources. The control system causes one pulse laser light source among the plurality of pulse laser light sources to emit light at a substantially constant output, and controls the pulse emission timing of another pulse laser light source to an arbitrary timing. The light source device according to claim 1. Further comprising a photoelectric sensor for detecting the amount of pulsed light synthesized by the synthesis optical system;
The control system is configured to detect the amount of pulsed light emitted from the plurality of pulsed laser light sources and passed through the combining optical system based on a detection result by the photoelectric sensor at the time of pulse emission of each of the plurality of pulsed laser light sources. The light source device according to claim 1, wherein the output is controlled. The combining optical system includes: a first optical integrator that receives laser light emitted from the plurality of pulse laser light sources in different regions and guides the laser light to a common incident surface; and a plurality of light incident on the common incident surface. The light source device according to claim 1, further comprising a second optical integrator that forms a plurality of light source images from laser light. The pulse emission frequency of the plurality of pulse laser light sources is 1.0 kHz to 4 kHz, and the control system causes the plurality of pulse laser light sources to alternately emit pulses at substantially equal time intervals. Item 5. The light source device according to any one of Items 1 to 4. The number of the plurality of pulse laser light sources is N (N is an integer greater than or equal to 2), the minimum pulse emission frequency of the plurality of pulse laser light sources is Rmin, and pulses required at the stage after being synthesized by the synthesis optical system When the frequency of light emission is f and the frequency f is smaller than N · Rmin,
The control system calculates α satisfying the following formula (α is an integer of 1 or more and (N−1) or less),
(N−α) · Rmin <f <N · Rmin
6. The light source device according to claim 1, wherein light emission of α pulse laser light sources among the N pulse laser light sources is stopped. In an exposure apparatus that illuminates a first object with an exposure beam from an exposure light source apparatus and exposes a second object through the first object with the exposure beam,
An exposure apparatus using the light source apparatus according to claim 1 as the exposure light source apparatus. The exposure apparatus according to claim 7, wherein the laser light is pulsed from a part of the plurality of pulse laser light sources. A method of controlling a light source device having a plurality of pulse laser light sources that emit laser light in pulses,
Controlling the plurality of pulse laser light sources, alternately emitting the laser light from the plurality of pulse laser light sources, and combining the laser light emitted from the plurality of pulse laser light sources into pulse light passing through a common optical path; A method for controlling a light source device. 10. The pulse light emission of one pulse laser light source among the plurality of pulse laser light sources is caused to emit light at a substantially constant output, and the pulse light emission timing of another pulse laser light source is controlled to an arbitrary timing. The light source device control method according to claim.

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