JPH07273014A - Light source for optical position detecting device and method thereof - Google Patents

Abstract

PURPOSE:To provide the simple structure light source for an optical position detector to be used for the optical position detecting device which detects the position of a wafer stage in a semiconductor aligner. CONSTITUTION:The title light source performs an additional function as the exposure light source for a semiconductor aligner, and it contains a light-path dividing means 40 to be used to take out a part of the laser beam from the exposure light source. The exposure light source is composed of (a): a laser light source 10 with which the second harmonic of the wavelength (lambda) can be emitted, (b): the second harmonic generating device 20 into which the laser beam from the exposure light source 10 is made incident and from which the laser beam of wavelength (N), based on the second harmonic of the above- mentioned incident light, and the laser beam of the wavelength (lambda) can be emitted, and (c): a resonator length control device 30 which controls the light of the resonator of the optical resonator. The position of a wafer stage 65 is detected by an optical position detecting device using the laser beam of wavelength (lambda) taken out from the light path dividing means 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source for a position detecting device used in an optical position detecting device for detecting the position of a wafer stage in a semiconductor exposure apparatus, and a wafer stage position detecting method.

[0002]

2. Description of the Related Art A semiconductor exposure apparatus is provided with a wafer stage (so-called XY stage). By moving the wafer stage by a combination of linear movements in the X direction and the Y direction, the wafer stage on which the wafer is placed can be moved to a predetermined position at high speed and with high accuracy. The wafer stage moving mechanism includes, for example, a DC servo motor and a ball screw connected to the wafer stage. The rotation of the DC servo motor is transmitted to the ball screw,
Move the wafer stage. As schematically shown in FIG. 7, a bar mirror 66 is attached to the wafer stage 65.

The position of the wafer stage 65 is measured by an optical position detector. The optical position detector is
For example, it is composed of a laser interferometer, more specifically, a plane mirror interferometer 50 and a receiver (light receiving device) 51. In this type of interferometer, a laser beam having a wavelength λ (having a frequency of f) emitted from a laser light source for an optical position detecting device composed of a He-Ne laser or an Ar laser is emitted from a plane mirror interferometer 50. The bar mirror 66 provided on the wafer stage 65 is irradiated with the light. The reflected light from the bar mirror 66 has a frequency that is Doppler-shifted according to the moving speed of the wafer stage 65, and reaches the receiver (light receiving device) 51 via the plane mirror interferometer 50 and the half mirror 52. The wafer stage 6
When the moving speed of 5 is v and the speed of light is c, the frequency change amount Δf of the Doppler-shifted laser light can be expressed by Δf = (v / c) f 2. An electric signal based on this Δλ is output from the receiver 51, and the relative position of the wafer stage is determined based on this output. A DC servo motor (not shown) is controlled so that the determined deviation amount between the relative position of the wafer stage 65 and the target position is 0 or a constant value.

In the semiconductor exposure apparatus, the wafer stage 65 is linearly moved in the X and Y directions in order to arrange the wafer at a predetermined position. During the coarse movement of the wafer stage 65, the wafer stage 65 is moved by the optical position detector.
Always measure the relative position of. Then, when the deviation amount between the current position of the wafer stage 65 and the target position reaches a predetermined value, the wafer stage 65 is stopped. Actually, even if the wafer stage 65 is stopped, the position of the stopped wafer stage deviates from the target position due to inertia. Therefore, the wafer stage 65 is finely moved by the wafer stage moving mechanism until the amount of deviation falls within the range of 0 or a predetermined value. Incidentally, such a wafer stage position adjusting method is usually called a closed loop method. On the other hand, there is also a method of slightly moving the wafer stage once or a predetermined number of times to complete the position adjustment of the wafer stage. Such a method is called an open loop method. The open loop method is an effective method when the relationship between the fine movement amount of the wafer stage and the deviation amount between the final wafer stage position and the target position is known.

[0005]

In the conventional optical position detecting device, as described above, the laser light source for the optical position detecting device including the He--Ne laser and the Ar laser is used. On the other hand, the semiconductor exposure apparatus is provided with an exposure light source composed of a laser light source, as shown in FIG. As described above, in the conventional semiconductor exposure apparatus,
There is a problem that a set of laser light sources is required, the apparatus becomes complicated, and at the same time, complicated maintenance is required. Further, in order to measure the relative position of the wafer stage 65 more accurately, it is desirable to use a laser light source that can emit laser light with a high frequency (that is, a short wavelength).

Therefore, it is a first object of the present invention to provide a light source for an optical position detecting device which does not require an independent light source for the optical position detecting device. A second object of the present invention is, in addition to the first object, to provide a light source for an optical position detecting device capable of measuring the position of a wafer stage with higher accuracy than ever before. A third object of the present invention is to provide a position detecting method for detecting the position of a wafer stage in a semiconductor exposure apparatus, which enables the wafer stage to be arranged at a predetermined position with higher accuracy than ever before. is there.

[0007]

A light source for an optical position detecting apparatus according to a first aspect of the present invention for achieving the above first object detects the position of a wafer stage in a semiconductor exposure apparatus. It is used for an optical position detection device. The light source for the optical position detecting device also serves as an exposure light source for the semiconductor exposure device, and includes an optical path splitting means for extracting a part of the laser light from the exposure light source. The exposure light source comprises (a) a laser diode, a solid-state laser medium made of Nd: YAG, and a nonlinear optical crystal element.
A laser light source capable of emitting a second harmonic of wavelength λ, and (b)
A laser beam having a wavelength λ emitted from the laser light source is made incident, which is composed of a nonlinear optical crystal element and an optical resonator, and a laser beam having a wavelength λ ′ based on the second harmonic of the incident light and a wavelength λ A second harmonic generation device capable of emitting laser light, and (c) a resonator length control device for controlling the resonator length of the optical resonator. Then, the position of the wafer stage is detected by the optical position detection device using the laser light of the wavelength λ extracted by the optical path splitting means.

In the light source for the optical position detecting device according to the first aspect of the present invention, the optical path splitting means is composed of a bandpass filter, and the laser light of the wavelength λ emitted from the second harmonic generating device is emitted. It can be taken out by an optical path splitting means. Alternatively, the optical path splitting means may be composed of a half mirror or a beam splitter, and a part of the laser light of wavelength λ emitted from the laser light source can be extracted by the optical path splitting means.

The light source for the optical position detecting device according to the second aspect of the present invention for achieving the above second object is further provided with a second optical path splitting means comprising a half mirror or a beam splitter. The optical path splitting means is composed of a bandpass filter, and among the laser light emitted from the second harmonic generation device by the optical path splitting means,
The laser light of wavelength λ is taken out, and a part of the laser light of wavelength λ ′ is taken out of the laser light emitted from the second harmonic generation device by the second optical path splitting means. It is characterized in that the position of the wafer stage is detected by an optical position detection device using a laser beam of wavelength λ ′.

The position detecting method for detecting the position of the wafer stage in the semiconductor exposure apparatus of the present invention for achieving the third object is such that the wafer stage is detected while detecting the position of the wafer stage with the laser beam of wavelength λ. Coarsely move
After moving the wafer stage near the desired position, finely move the wafer stage while detecting the position of the wafer stage with laser light of wavelength λ '(where λ'<λ), and move the wafer stage to the desired position. It is characterized by comprising the step of arranging.

In the position detecting method of the present invention, the laser light can be a part of the laser light emitted from the exposure light source for the semiconductor exposure apparatus. In this case, the wavelength is λ
It is preferable to use laser light that satisfies the relationship of = 2λ '.

[0012]

Since the light source for the optical position detecting device of the present invention also serves as the exposure light source for the semiconductor exposure device, two laser light sources are not required unlike the prior art. A laser beam of wavelength λ ′ and a laser beam of wavelength λ are emitted from the second harmonic generation device. Then, the laser light of wavelength λ ′ is provided to expose the resist formed on the wafer. Although it depends on the wavelength λ, the resist formed on the wafer is not exposed by the laser light of the wavelength λ. Therefore, even if the laser light of the wavelength λ is taken out as the light source for the optical position detecting device during the exposure of the resist, the efficiency as the exposure light source for the semiconductor exposing device is not lowered. In the light source for the optical position detecting device according to the second aspect of the present invention, a part of the laser light having the wavelength λ ′ is used as a light source for the optical position detecting device, but the amount of light is insignificant. Therefore, the efficiency as the exposure light source for the semiconductor exposure apparatus does not decrease significantly.

In the light source for the optical position detecting device according to the second aspect of the present invention and the position detecting method of the present invention,
A part of the laser light of wavelength λ ′ and the laser light of wavelength λ are used as a light source for the optical position detecting device. By using the laser light of two kinds of wavelengths in this way, Δf =
As is clear from the equation (v / c) f, the position of the wafer stage can be measured with high accuracy.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

(Embodiment 1) A light source for an optical position detecting device according to a first embodiment relates to a light source for an optical position detecting device according to the first aspect of the present invention. FIG. 1 shows a principle diagram of a light source for an optical position detecting device, an optical position detecting device, and a semiconductor exposure apparatus in the first embodiment. The light source for the optical position detecting device of the first embodiment also serves as an exposure light source for a semiconductor exposure device, and includes an optical path splitting means 40 for extracting a part of laser light from this exposure light source.

This exposure light source comprises a laser light source 10 and a second light source.
It is composed of a harmonic generator 20 and a resonator length controller 30. As shown in the schematic view of FIG.
Reference numeral 0 is composed of a laser diode 11, a solid-state laser medium 12 made of Nd: YAG, and a nonlinear optical crystal element 13, and can emit a second harmonic of wavelength λ. The second harmonic generation device 20 is composed of a non-linear optical crystal element 21 and an optical resonator 22, receives laser light of wavelength λ emitted from the laser light source 10, and receives the second harmonic of this incident light. The laser light having the wavelength λ ′ and the laser light having the wavelength λ are emitted. The resonator length control device 30 controls the resonator length of the optical resonator 22.

The laser light of wavelength λ extracted by the optical path splitting means 40 is used as a light source for the optical position detecting device. In the light source for the optical position detecting device of the first embodiment, the optical path splitting means 40 is composed of a bandpass filter, and the laser light (wavelengths λ ′ and λ) emitted from the second harmonic generation device 20 is included. , The laser light of wavelength λ is taken out by the optical path splitting means 40, and the wafer stage 65 is driven by the optical position detecting device using the laser light of wavelength λ.
Detect the position of.

The laser light of the wavelength λ ′ emitted from the second harmonic wave generator 20 passes through the reflecting mirror 60 and the reticle 61.
And the pattern formed on the reticle 61 is transferred to the resist 64 formed on the wafer 63 via the reduction projection lens 62. The pattern formed on the reticle 61 is a pattern to be formed on the resist 64 magnified five times, for example. The reduction projection lens 62 transmits the incident laser light and projects an optical image reduced to, for example, 1/5, onto the resist 64 formed on the wafer 63. As a result, a fine pattern is formed on the resist 64.

The wafer 63 is a wafer chuck (not shown).
Placed on. This wafer chuck has a wafer stage 6
It is attached to 5. A bar mirror 65 is attached to the wafer stage 65. Note that, in FIG. 1, only the bar mirrors in one direction (for example, the X direction) are illustrated, but the bar mirrors are attached in the other directions (for example, the Y direction). The wafer stage 65 is moved in the X and Y directions by a conventional wafer stage moving mechanism (not shown). The wafer stage moving mechanism includes a DC servo motor and a ball screw connected to the wafer stage. The rotation of the DC servo motor is transmitted to the ball screw to move the wafer stage.

The optical position detecting device comprises, for example, a plane mirror interferometer 50, a receiver (light receiving device) 51 and a half mirror 52. The plane mirror interferometer 50 is a known interferometer in which a polarization beam splitter, two corner cube reflectors, and a quarter wave plate are combined. The receiver 51 can be composed of, for example, a photodiode. Two sets of optical position detectors are provided to detect the movement of the wafer stage in the X direction and the Y direction.

In order to measure the position of the wafer stage 65, it is emitted from the second harmonic generator 20, extracted by the optical path splitting means 40 comprising a bandpass filter, and passed through the half mirror 52 and the plane mirror interferometer 50. The bar mirror 66 is irradiated with laser light of wavelength λ (frequency f).
Irradiate. Since the bar mirror 66 moves together with the wafer stage 65, the Doppler shift occurs in the laser light reflected by the bar mirror 66. Normally, the laser light reflected by the bar mirror 66 and incident on the plane mirror interferometer 50 is emitted again from the plane mirror interferometer 50 toward the bar mirror 66 and is reflected by the bar mirror 66 again. In this way, by being reflected twice by the bar mirror 66, the Doppler shift amount of the laser light can be doubled (2Δf), and the accuracy is improved. Further, since the laser light passes through the quarter-wave plate four times in total, the phase shifts by π.

Finally, the plane mirror interferometer 5
This laser light (frequency is f ± 2Δf) passing through 0 is received by the receiver 51 via the half mirror 52. On the other hand, the wavelength λ reflected from the plane mirror interferometer 51
A laser beam of (frequency f) (however, the laser beam reflected by the bar mirror 66 is out of phase with π) is also incident on the receiver 51. As a result, the receiver 51 outputs a signal having a frequency difference 2Δf. Based on this output, the relative position of wafer stage 65 is determined. The DC servo motor (not shown) is controlled by the closed loop method or the open loop method so that the deviation amount between the determined relative position of the wafer stage 65 and the target position becomes 0 or a constant value. To do. The position detecting method for detecting the position of the wafer stage using the optical position detecting device described in the first embodiment is a known method.

FIG. 2 shows a more detailed block diagram of the exposure light source for the semiconductor exposure apparatus used in the first embodiment. As shown in FIG. 2, the exposure light source for the semiconductor exposure apparatus of the first embodiment is
The laser light source 10 is capable of emitting the second harmonic. The laser light source 10 includes a plurality of laser diodes 11
(Wavelength of emitted light: 808 nm), solid-state laser medium 12 made of Nd: YAG (wavelength of emitted light: 1064 nm),
And an LD-pumped solid-state laser composed of a nonlinear optical crystal element 13 made of KTP (KTiOPO ₄ ). The solid-state laser medium 12 is of an end face excitation type. With such a configuration, from the laser light source 10, the second harmonic of the solid-state laser medium made of Nd: YAG is 532 nm (=
Laser light having a wavelength of λ) is emitted. In the laser light source 10, a quarter-wave plate 14 is arranged in front of the solid-state laser medium 12 made of Nd: YAG. As a result, in the laser light source 10, it is possible to suppress multimode oscillation due to the so-called hole burning effect.

The nonlinear optical crystal element 13 is arranged in the optical path of the optical resonator consisting of the plane mirror 15 and the concave mirror 16, and is a so-called external SHG system (a system arranged in an optical resonator formed outside the laser oscillator). Make up. Plane mirror 15
Reflects most of the light. The concave mirror 16 is Nd: YA
It transmits most of the second harmonics of the solid-state laser medium made of G and reflects most of the light having other wavelengths. Concave mirror 1
6 can be constituted by a dichroic mirror, for example.

As shown in FIG. 2, the second harmonic generation device 2
0 is composed of a nonlinear optical crystal element 21 made of, for example, BBO (β-BaB ₂ O ₄ ) and an optical resonator 22. In the first embodiment, the nonlinear optical crystal element 21 that constitutes the second harmonic generation device 20 is arranged in the optical path of the optical resonator 22. That is, the second harmonic generation device 20
Is a so-called external SHG method. In this optical resonator 22, the so-called finesse value (corresponding to the Q value of resonance) is increased to, for example, about 100 to 1000, and the optical resonator 22 is increased.
To effectively use the non-linear effect of the non-linear optical crystal element 21 arranged in the optical resonator 22 by making the internal light density several hundred times the light density of the light incident on the optical resonator 22. You can

The optical resonator 22 includes a pair of concave mirrors 23 and 24.
And a pair of plane mirrors 25 and 26. Second
Light incident on the harmonic generation device 20 (for example, λ = 532
(light having a wavelength of nm) passes through the first concave mirror 23 and the nonlinear optical crystal element 21 and is at least partially converted into a second harmonic (for example, light having a wavelength λ ′ = 266 nm). , Reflected by the second concave mirror 24, then
It is reflected by the plane mirrors 25 and 26, and further reflected by the first concave mirror 23. In such a state, the light incident on the second concave mirror 24 (for example, the wavelength λ ′
= 266 nm light) and at least a part of the second concave mirror 2
4 and is emitted from the second harmonic generation device 20 toward the optical path splitting means 40. The second harmonic generator 2
In the laser light emitted from 0 toward the optical path splitting means 40, not only the laser light of λ ′ = 266 nm but also λ =
Laser light of 532 nm is also included.

Further, a part of the light incident on the first concave mirror 23 from the plane mirror 26 (for example, light having a wavelength of 532 nm).
Passes through the first concave mirror 23 and enters a resonator length control device 30 described later. Incidentally, the first and second concave mirrors 2
3, 24 and the plane mirrors 25, 26 are designed to reflect and transmit light as described above. Second concave mirror 24
Can be composed of, for example, a dichroic mirror.

The wavelength λ ′ of the light emitted from the second harmonic generation device 20 is based on the laser light (wavelength = λ) incident on the second harmonic generation device 20, and the second
It is a harmonic. That is, in the first embodiment, the wavelength λ of the incident light entering the second harmonic generation device 20 from the laser light source 10 is 532 nm, and the wavelength λ ′ of the laser light emitted from the second harmonic generation device 20 is The laser light having a wavelength of 266 nm (= 532 nm) is emitted at the same time.
Based on the wavelength (1064 nm) of the laser light emitted from the solid-state laser medium 12 made of Nd: YAG, the laser light having the wavelength λ ′ emitted from the second harmonic generation device 20 is the fourth harmonic. Equivalent to. Laser light having a narrow band of wavelengths 266 nm and 532 nm is continuously emitted from the second harmonic generation device 20, and the mode uniformity of such light is high.

The resonator length (L) of the optical resonator 22 is precisely controlled by the resonator length control device 30 and is maintained at a constant length. By precisely maintaining the resonator length (L) of the optical resonator 22 at a constant length, the intensity of the laser light of wavelength λ ′ emitted from the second harmonic generation device 20 can be maintained at a constant level. . The cavity length (L) is equal to that of the first concave mirror 2
3, the second concave mirror 24, the plane mirror 25, the plane mirror 26, and the first concave mirror 23 are equivalent to the optical path length connecting the reflecting surfaces.

When the wavelength of the emitted light emitted from the second harmonic generation device 20 is λ ′, the resonator length L ₀ of the optical resonator 22 is λ ′ = L ₀ / M (where M is a positive value). When it satisfies the condition (also referred to as a lock state), the optical resonator 22 resonates, and the second harmonic generation device 20 stably emits high-intensity light.
In other words, the optical path phase difference Δ in the optical resonator 22 is 2
When it is an integral multiple of π, the optical resonator 22 forming the second harmonic generation device 20 is in a resonance state. That is, the lock state is set. Here, when the refractive index of the nonlinear optical crystal element 21 is n and the thickness is 1, the optical path phase difference Δ is (4πnl / λ ′).
Can be expressed as

Further, the resonator length of the optical resonator 22 L ₀ ± ΔL ₀
Is λ '≠ (L ₀ ± ΔL ₀ ) / M' (where M'is a positive number)
At this time (also referred to as an unlocked state), the second harmonic generation device 20 emits light of low intensity. In other words, when the optical path phase difference Δ in the optical resonator 22 deviates from an integer multiple of 2π, the optical resonator 22 forming the second harmonic wave generating device 20.
Becomes a non-resonant state. That is, the unlocked state is set.

Therefore, in order to stably emit the light of the wavelength λ ′ from the second harmonic generation device 20, the resonator length (L) of the optical resonator 22 changes with time (specifically, for example, , The positions of the concave mirrors 23 and 24 and the plane mirrors 25 and 26 must be minimized. Therefore, under the control of the resonator length control device 30, the first concave mirror 23 is moved on the optical axis connecting the first concave mirror 23 and the second concave mirror 24, or the first concave mirror 23 with respect to the optical axis. By changing the arrangement angle of the optical resonator 22 to suppress the temporal change of the resonator length (L) of the optical resonator 22 and keep the resonator length (L) of the optical resonator 22 constant.

Resonator length control device 30 in the first embodiment
Is described in detail in "Laser Light Generator" (Japanese Patent Laid-Open No. 5-243661) filed by the applicant on March 2, 1992.

A resonator length control device 30 of this type is shown in FIG.
As shown in FIG. 3, it comprises a photodetector 31 such as a photodiode, a voice coil motor (VCM) 32, a voice coil motor control circuit (VCM control circuit) 33, and a phase modulator 34. The phase modulator 34 includes a laser light source 10 and a second light source.
It is arranged in the optical path between the harmonic generator 20 and
A so-called E for phase-modulating the light emitted from the laser light source 10
It is composed of an O (electro-optic) element and an AO (acousto-optic) element.
Between the phase modulator 34 and the second harmonic generation device 20,
A condenser lens 35 is arranged. The voice coil motor 32 is attached with a first concave mirror 23 that constitutes the optical resonator 22.

As shown in the schematic view of FIG. 3, the voice coil motor 32 includes a base 320 made of a magnetic material, one or more electromagnets (so-called voice coils) 322, a yoke 323 made of a magnetic material, and at least one coil spring. (Or a spiral leaf spring) 321 is an electromagnetic actuator. The coil spring 321 has one end attached to the base 320 and the other end attached to the yoke 323. The first concave mirror 23 and the electromagnet 322 are attached to the yoke 323. When a current is applied to the electromagnet 322, a magnetic field is formed and the yoke 3
The distance between 23 and the base 320 changes. as a result,
The position of the first concave mirror 23 can be moved. That is, by controlling the current flowing through the electromagnet 322,
The resonator length (L) of the optical resonator 22 can be changed. Servo control is performed on the voice coil motor 32.

The drive current of the voice coil motor 32 is about several tens to several hundreds mA. Therefore, the drive circuit configuration can be manufactured at low cost. Moreover, the frequency of multiple resonance of the servo loop can be set to several tens of kHz to 100 kHz or more, and since the frequency characteristics with few phase rotations are provided, the servo band can be widened to several tens of MHz and stable control can be performed. Obtainable.

When the optical resonator 22 is in the lock state, for example, the intensity of light emitted from the first concave mirror 23 and reaching the photodetector 31 is minimized, and the phase of the light is greatly changed. Controlling an optical resonator using such changes is described in, for example, RWP Drever, et al. "Lase
r Phase and Frequency Stabilization Using an Optic
al Resonator ", Applied Physics B31. 97-105 (1983). Control of the locked state of the optical resonator 22 is described in
Basically, this technology is applied.

That is, for example, through the first concave mirror 23,
If the VCM control circuit 33 drives the voice coil motor 32 to change the position of the first concave mirror 23 so that the intensity of the light reaching the photodetector 31 is always a minimum value (for example, 0), The locked state of the resonator 22 can be stably maintained. In other words, the light emitted from the laser light source 10 is phase-modulated based on the phase-modulated signal, is incident on the second harmonic generation device 20, and the return light from the second harmonic generation device 20 is detected by the photodetector 31. A detection signal is obtained by detecting with. Then, the detection signal is
Synchronous detection is performed using the phase modulation signal and an error signal is extracted. The VCM control circuit 33 drives the voice coil motor 32 so that this error signal becomes 0, and the first concave mirror 2
Change the position of 3.

The VCM control circuit 33 has, for example, an oscillator 330, a phase modulator drive circuit 331, a synchronous detection circuit 332, a low-pass filter 33, as shown in the configuration diagram of FIG.
3 and a voice coil motor drive circuit (VCM drive circuit) 334.

The frequency f output from the oscillator 330
_{The m} (for example, 10 MHz) modulation signal is sent to the phase modulator 34 via the phase modulator driving circuit 331. In the phase modulator 34, the light emitted from the laser light source 10 (frequency f _{O, on the} order of 10 ¹⁴ Hz) is subjected to phase modulation, and sidebands having a frequency f _O ± f _m are generated.

The first concave mirror 23 constituting the optical resonator 22.
The light (frequency: f _O and f _O ± f _m ) that has passed through and exited the system of the optical resonator 22 is detected by the photodetector 31. The FM sideband method for detecting the beat between the light having such a frequency (f _O and f _O ± f _m), it is possible to obtain an error signal having a polarity, such on the basis of the error signal optical resonator 22 Control the cavity length (L) of the.

That is, the signal output from the photodetector 31 is sent to the synchronous detection circuit 332. This signal is a signal in which a light intensity signal of frequency f _O and a signal corresponding to a modulation signal of frequency f _m are superimposed. Synchronous detection circuit 33
The modulated signal output from the oscillator 330 (with waveform shaping and phase delay applied as necessary) is also supplied to 2. The signal output from the photodetector 31 and the modulated signal are multiplied in the synchronous detection circuit 322 to perform synchronous detection. The detection output signal output from the synchronous detection circuit 332 is input to the low-pass filter 333. By removing the modulation signal component from the detection output signal in the low-pass filter 333, an error signal of the resonator length of the optical resonator 22 is generated. To be done. Here, the error signal means the measured resonator length (L ₀ ± ΔL ₀ ) with respect to the set resonator length (L ₀ ) of the optical resonator 22.
Is a signal representing the difference (± ΔL ₀ ).

This error signal is sent to the VCM drive circuit 334, and the voice coil motor 32 is based on this error signal.
Are driven (specifically, by controlling the current flowing through the electromagnet 322), the light is transmitted through the first concave mirror 23 and the photodetector 3
So that the light reaching 1 has a minimum value (in other words,
The resonator length (L) of the optical resonator 22 is adjusted so that the resonator length of the optical resonator 22 becomes L ₀ and the error signal becomes 0).

When the resonator length (L) of the optical resonator 22 is set to L ₀ (that is, in the locked state), the resonator length controller 30 controls the resonator length of the optical resonator 22. (L) changes over time (specifically, for example, changes in the positions of the concave mirrors 23 and 24 and the plane mirrors 25 and 26)
1/10 of the wavelength of light incident on the second harmonic generation device 20
It can be suppressed to 00 to 1/10000.

(Embodiment 2) Embodiment 2 is a modification of Embodiment 1. In the first embodiment, the second harmonic generation device 20
The laser light of wavelength λ out of the laser light of wavelength λ ′ and the laser light of wavelength λ emitted from was extracted by the optical path splitting means 40. On the other hand, in the second embodiment, the optical path splitting means 41 is composed of a half mirror or a beam splitter, and a part of the laser light of the wavelength λ emitted from the laser light source 10 is extracted by the optical path splitting means 41, and the optical type It is used as the light source of the position detector.

FIG. 5 shows a principle diagram of the position detecting device including the light source for the optical position detecting device and the semiconductor exposure device in the second embodiment. Except for the difference in the structure and arrangement of the optical path splitting means 41, the other constituent elements can be the same as those in the first embodiment, and detailed description thereof will be omitted.

(Embodiment 3) The light source for the optical position detecting device of the embodiment 3 detects the light source for the optical position detecting device of the second aspect of the present invention and the position of the wafer stage in the semiconductor exposure apparatus. The present invention relates to a position detecting method of the present invention. FIG. 6 shows a principle diagram of a position detecting device including a light source for an optical position detecting device and a semiconductor exposure apparatus in the third embodiment.
The light source for the optical position detecting device of the third embodiment also serves as the exposure light source for the semiconductor exposure device, and the optical path splitting means 42 and the second optical path splitting part for extracting a part of the laser light from this exposure light source. Means 43 are included. In the third embodiment, the optical path splitting means 42 is a bandpass filter, and the second optical path splitting means 43 is a half mirror or a beam splitter. Then, the laser light of wavelength λ is extracted from the laser light emitted from the second harmonic generation device 20 by the optical path splitting means 42, and the laser light of the wavelength λ is extracted from the second harmonic generation device 20 by the second optical path splitting means 43. A part of the laser light having the wavelength λ ′ is extracted from the emitted laser light, and the position of the wafer stage 65 is detected by the optical position detecting device using the laser light having the wavelength λ and the wavelength λ ′.

The exposure light source is composed of a laser light source 10, a second harmonic generation device 20, and a resonator length control device 30, like the exposure light source in the first embodiment shown in FIG. The configuration of the optical position detector can be the same as that of the first embodiment.

In the position detecting method for detecting the position of the wafer stage in the third embodiment, first, the laser light emitted from the second harmonic generation device 20 is extracted by the optical path splitting means 42 including a bandpass filter. The wafer stage 65 is roughly moved while detecting the position of the wafer stage 65 with the laser light having the wavelength λ (λ = 532 nm in the third embodiment), and the wafer stage is moved to the vicinity of the desired position. That is, the wafer stage 65 is linearly moved at high speed in the X and Y directions. Wafer stage 6
During the coarse movement of 5, the relative position of the wafer stage 65 is constantly measured by the optical position detector. Then, when the deviation amount from the target position reaches a predetermined value, the wafer stage 65 is stopped.

Even if the wafer stage 65 is stopped, the stopped position of the wafer stage 65 is displaced from the target position due to inertia. Therefore, the wafer stage is finely moved while detecting the position of the wafer stage with the laser light of the wavelength λ ′ (λ ′ = 266 nm in the third embodiment) until the deviation amount falls within the range of 0 or a predetermined value. . The laser light of the wavelength λ ′ is a part of the laser light of the wavelength λ ′ in the laser light emitted from the second harmonic generation device 20 that is extracted by the second optical path splitting unit 43. Then, the wafer stage 65 is finely moved to place the wafer stage 65 at a desired position. Either a closed loop method or an open loop method may be adopted as the wafer stage position adjusting method. The incidence of the laser light having the wavelength λ and the laser light having the wavelength λ ′ on the optical position detecting device can be controlled by a shutter mechanism (not shown).

The present invention has been described above based on the preferred embodiments, but the present invention is not limited to these embodiments. The structures of the laser light source 10, the second harmonic generation device 20, the resonator length control device 30, and the optical position detection device are examples, and the design can be appropriately changed.

The solid-state laser medium can be composed of Nd: YVO ₄ , Nd: BEL, LNP, etc., in addition to Nd: YAG. The pumping method of the solid-state laser medium by the laser diode can be not only the edge pumping method but also the side pumping method and the surface pumping method, and further, a slab solid-state laser can be used. In addition to KTP and BBO, non-linear optical crystal elements include LN and QPM.
LN, LBO, KN or the like can be appropriately selected depending on the wavelength of light required for incident light or emitted light.

It is also possible to use a so-called internal SHG type laser light source in which a solid-state laser medium and a nonlinear optical crystal element are arranged in the optical path of an optical resonator composed of a pair of reflecting mirrors.
Further, it is also possible to adopt a structure in which light emitted from the solid-state laser medium 12 is passed through the nonlinear optical crystal element 13 (that is, a structure in which the optical resonator including the plane mirror 15 and the concave mirror 16 is omitted). Further, as the laser light source, for example, a blue semiconductor laser can be used instead of the LD pumped solid-state laser, and the emitted light of such a semiconductor laser can be directly incident on the second harmonic generation device, or it can be nonlinear with the semiconductor laser. It is also possible to have a combination structure of a laser light source of a so-called internal SHG system in which an optical crystal element is combined and a second harmonic generation device. Further, a resonator length control device 30 may be separately provided for controlling the resonator length of the optical resonator including the plane mirror 15 and the concave mirror 16.

The structure of the optical resonator 22 in the second harmonic generator 20 may be, for example, a Fabry-Perot type resonator composed of a concave mirror and a plane mirror. In this case, a reflecting mirror that transmits the incident light incident on the second harmonic generation device 20 and reflects the returned light from the second harmonic generation device 20 is arranged in front of the second harmonic generation device 20. The light reflected by the reflecting mirror may be detected by the photodetector 31. In order to change the resonator length of the optical resonator 22, not only the first concave mirror 23 may be moved but other mirrors may be moved.

As another mode of the resonator length control device 30,
An example of the resonator length control device is PZT. That is, in order to move the first concave mirror 23 forming the optical resonator 22, a laminated piezoelectric element made of PZT or the like and a signal proportional to the length change of the resonator length (L) are supplied to this laminated piezoelectric element. A resonator length control device including a control device is used to feed back such a signal to form a servo loop. Thereby, the resonator length of the optical resonator 22 can be controlled, and the intensity of the emitted light emitted from the second harmonic generation device 20 can be controlled.

A part of the laser light emitted from the second harmonic generation device is a laser light having a wavelength (λ ') based on the second harmonic of the incident light from the laser light source. The wavelength (λ ') of the light emitted from the harmonic generator is
As described in the embodiment, not only the fourth harmonic wave based on the light emitted from the solid-state laser medium but also the fifth harmonic wave can be used. In this case, the light emitted from the solid-state laser medium made of Nd: YAG (wavelength: 106, for example)
4 nm) and the light (wavelength: 266 nm) emitted from the second harmonic generation device 20 are combined, and another second harmonic generation device 20 (for example, urea CO of an organic crystal as a nonlinear optical crystal element) is synthesized again. (NH ₂ ) ₂ is used to pass the fifth of the solid-state laser medium composed of Nd: YAG.
A harmonic wave (wavelength: 213 nm) can be generated.

[0057]

Since the light source for the optical position detecting device of the present invention also serves as the exposure light source for the semiconductor exposure device, it does not require two laser light sources unlike the prior art. Therefore, the configuration of the entire semiconductor exposure apparatus is simplified and maintenance is facilitated. Moreover, the efficiency of the exposure light source does not decrease to the left. In the light source for the optical position detecting device according to the second aspect of the present invention and the position detecting method of the present invention, a part of the laser light of wavelength λ ′ and the laser light of wavelength λ are used for the optical position detecting device. Since it is used as a light source, the position detection resolution of the wafer stage becomes high and the position of the wafer stage can be measured with high accuracy.

[Brief description of drawings]

FIG. 1 is a principle diagram of a light source for an optical position detection device, an optical position detection device, and a semiconductor exposure apparatus according to a first embodiment.

FIG. 2 is a diagram showing an outline of an exposure light source.

FIG. 3 is a schematic diagram of a voice coil motor.

FIG. 4 is a configuration diagram of a VCM control circuit that constitutes a resonator length control device.

FIG. 5 is a principle diagram of a light source for an optical position detecting device, an optical position detecting device, and a semiconductor exposure apparatus according to a second embodiment.

FIG. 6 is a principle diagram of a light source for an optical position detecting device, an optical position detecting device, and a semiconductor exposure apparatus according to a third embodiment.

FIG. 7 is a principle diagram of a light source for an optical position detecting device, an optical position detecting device, and a semiconductor exposure apparatus of the related art.

[Explanation of symbols]

 10 Laser Light Source 11 Laser Diode 12 Solid State Laser Medium 13 Nonlinear Optical Crystal Element 14 Quarter Wave Plate 15 Plane Mirror 16 Concave Mirror 20 Second Harmonic Generator 21 Nonlinear Optical Crystal Element 22 Optical Cavity 23 First Concave Mirror 24 Second Concave mirror 25, 26 Plane mirror 30 Resonator length control device 31 Photodetector 32 Voice coil motor 320 Base body 321 Coil spring 322 Electromagnet 323 Yoke 40, 41, 42 Optical path splitting means 43 Second optical path splitting means 50 Plane mirror interferometer 51 Receiver 52 Half mirror 60 Reflective mirror 61 Reticle 62 Reduction projection lens 63 Wafer 64 Resist 65 Wafer stage 66 Bar mirror

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03F 9/00 H

Claims (7)

[Claims] 1. A light source for an optical position detection device used in an optical position detection device for detecting the position of a wafer stage in a semiconductor exposure device, wherein the light source is an exposure light source for the semiconductor exposure device. And
The exposure light source includes an optical path dividing unit for extracting a part of the laser light from the exposure light source, and the exposure light source has a wavelength composed of a laser diode, a solid-state laser medium made of Nd: YAG, and a nonlinear optical crystal element. a laser light source capable of emitting the second harmonic of λ, and (b) a nonlinear optical crystal element and an optical resonator, into which the laser light of wavelength λ emitted from the laser light source is incident,
And a second harmonic generation device capable of emitting laser light of wavelength λ ′ and laser light of wavelength λ based on the second harmonic of the incident light; and (c) controlling the resonator length of the optical resonator. An optical position detecting device for detecting the position of the wafer stage by the optical position detecting device using the laser light of wavelength λ extracted by the optical path splitting means. Light source. 2. The optical path splitting means according to claim 1, wherein the optical path splitting means comprises a bandpass filter, and the laser light having a wavelength λ emitted from the second harmonic generation device is taken out by the optical path splitting means. Light source for position detection device. 3. The optical path splitting means is composed of a half mirror or a beam splitter, and has a wavelength λ emitted from a laser light source.
2. The light source for an optical position detecting device according to claim 1, wherein a part of the laser light of is extracted by the optical path splitting means. 4. A second optical path splitting means comprising a half mirror or a beam splitter is further provided, and the optical path splitting means comprises a bandpass filter, and the optical path splitting means emits light from the second harmonic generation device. Of the laser light, the laser light of wavelength λ is taken out, and by the second optical path splitting means, a part of the laser light of wavelength λ ′ is taken out of the laser light emitted from the second harmonic generation device, 2. The light source for an optical position detecting device according to claim 1, wherein the position of the wafer stage is detected by the optical position detecting device using the laser light having the wavelength λ and the wavelength λ ′. 5. A position detecting method for detecting the position of a wafer stage in a semiconductor exposure apparatus, wherein the wafer stage is roughly moved while detecting the position of the wafer stage with a laser beam having a wavelength λ, and the vicinity of the desired position is obtained. After moving the wafer stage to the wavelength λ '(where λ'<
A method for detecting a position of a wafer stage, which comprises a step of finely moving the wafer stage while detecting the position of the wafer stage with a laser beam of λ) and disposing the wafer stage at a desired position. 6. The method for detecting the position of a wafer stage according to claim 5, wherein the laser light is a part of the laser light emitted from the exposure light source for the semiconductor exposure apparatus. 7. The method for detecting the position of a wafer stage according to claim 6, wherein the wavelength of the laser light satisfies the relationship of λ = 2λ ′.