JP2001083472A - Optical modulating device, light source device and exposure source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a train of pulses while keeping an enough extinction ratio. SOLUTION: A correction signal VB to correct the main modulation signal VP as the pulse train signal to modulate the pulse train is generated by a correction signal generator 330 based on the monitoring result of the light emitted from a light modulator 310 in the period except for the period of emitting light pulses in the modulation period for the pulse train. The corrected signal of the main modulation signal VP by the correction signal VB is supplied as a modulation signal VC to the light modulator 310. As a result, the extinction ratio in the period except for the period of emitting the light pulses in the modulation period of the pulse train can be kept to an enough value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light modulation device, a light source device, and an exposure device, and more particularly, to a light modulation device for modulating a pulse train of incident light, a light source device having the light modulation device, and the light source. The present invention relates to an exposure apparatus provided with an apparatus.

[0002]

2. Description of the Related Art Conventionally, in a lithography process for manufacturing a semiconductor device (integrated circuit), a liquid crystal display device and the like,
Various exposure apparatuses are used. In recent years, as this type of exposure apparatus, a fine circuit pattern formed on a photomask or a reticle is reduced and projected via a projection optical system onto a substrate such as a wafer or a glass plate having a surface coated with a photoresist. A reduction projection exposure apparatus such as a so-called stepper or a so-called scanning stepper for transferring and transferring data has become mainstream because of its high throughput.

One basic function of such an exposure apparatus such as a projection exposure apparatus is an exposure amount control function for keeping the integrated exposure amount (integrated exposure energy) for each point in each shot area of a wafer within an appropriate range. There is. In such exposure amount control, in recent years, a method of controlling the exposure amount with high accuracy by using a pulse light source and performing pulse number control and pulse power control has attracted attention.

A typical example of such a pulse light source is a KrF excimer laser (wavelength: 248 nm). At present, an exposure apparatus using an ArF excimer laser (wavelength: 193 nm) as a light source having a shorter wavelength has been developed. I have.

However, the above-mentioned excimer laser is large, the energy per pulse is large, and the optical parts are easily damaged, and the maintenance of the laser is complicated and costly because toxic fluorine gas is used. There are disadvantages, such as high cost, as a light source of the exposure apparatus.

For this reason, a laser light source that emits long-wavelength light (infrared light, visible light) such as a semiconductor laser is used as a laser light source, and the laser light is converted into short-wavelength ultraviolet light by using the nonlinear optical effect of a nonlinear optical crystal. For example, Japanese Patent Application Laid-Open No. 8-334803 discloses a method of converting and using ultraviolet light thus obtained as exposure light.
Has been proposed.

[0007]

In order to obtain a pulse output from the reference light source in the light source utilizing the nonlinear optical effect, light emitted from a semiconductor laser or the like is used by using an electro-optical effect (EO effect). A method of performing pulse modulation using a waveguide type optical interferometer is generally used. However, the use of the current optical modulator has only resulted in an amplifier having low pulse width efficiency.

The reason is that the extinction ratio between light pulses is not sufficient in the current optical modulator. That is, even when the optical modulator is set to a sufficient extinction ratio at the beginning, the extinction ratio may fluctuate with time due to a temperature change or the like, and may reduce the accuracy of the exposure amount control by the pulse number control or the like. That's why.

The present invention has been made under the above circumstances, and a first object of the present invention is to provide an optical modulation device capable of maintaining a sufficient extinction ratio.

It is a second object of the present invention to provide a light source device capable of controlling the amount of emitted light with high accuracy.

A third object of the present invention is to provide an exposure apparatus capable of improving the exposure accuracy by controlling the exposure amount with high accuracy.

[0012]

A first light modulation device according to the present invention is a light modulation device that modulates a pulse train of incident light and emits the light, and has a transmittance substantially equal to 0 according to the value of the first modulation signal. The first optical modulator (3
10); a first pulse generator (320) for generating a first main modulation signal toward the first optical modulator; and the light in a period other than each light pulse emission period in the pulse train modulation period. A first correction signal for correcting the first main modulation signal in order to make emission light from the optical modulator zero during a period other than the light pulse emission period based on a monitoring result of emission light from the modulator. And a correction signal generator (330) for generating the light.

According to this, the correction signal generator causes the correction signal generator to perform the pulse train modulation based on the monitoring result of the light emitted from the first optical modulator during a period other than each light pulse emission period within the pulse train modulation period. A first correction signal for correcting the first main modulation signal, which is a pulse train signal for the first time, is generated. And
Since the signal obtained by correcting the first main modulation signal by the first correction signal is supplied to the first optical modulator as a first modulation signal, the extinction ratio in a period other than each light pulse emission period in the pulse train modulation period is determined. It can be maintained at a sufficient value.

In the first light modulation device of the present invention, the correction signal generator corrects the intensity of the light emitted from the first light modulator to a predetermined intensity during a period other than the pulse train modulation period. It may be configured to further generate a signal. In such a case, when there is an optical fiber amplifier on the downstream side of the optical modulator, the amplification factor of the optical fiber amplifier immediately after the start of pulse train modulation can be made closer to the gain after a while after the start of pulse train modulation. . Therefore, the pulse power of each light pulse of the light pulse train emitted from the optical fiber amplifier can be made uniform.

In this case, it is preferable that the predetermined intensity is an average intensity of light emitted from the optical modulator during the period of the pulse train modulation. This is because the average light quantity to be amplified by the optical fiber amplifier is always constant, and the gain of the optical fiber amplifier can be constant.

Further, in the first light modulation device of the present invention, the first modulation signal may be an electric signal, and the first light modulator may be an electro-optic modulator. In such a case, light modulation can be performed by an electric signal that is easy to control and process.

Here, the first modulation signal is a voltage signal, and the first optical modulator splits the incident light into a first light and a second light, and a first optical demultiplexer; A first optical waveguide (312) that guides the first light; a second optical waveguide (313) that guides the second light and changes a refractive index according to an applied voltage value; A first for applying a voltage based on the first modulation signal to at least a part of the second optical waveguide;
A configuration including an electrode and (315a, 315b); a first multiplexer for multiplexing the first light via the first waveguide and the second light via the second waveguide. It can be. In such a case, by adjusting the voltage applied to the first electrode and adjusting the difference in optical path length between the first optical waveguide and the second optical waveguide, it is possible to modulate the light emitted from the first optical modulator. it can.

In this case, the correction signal generator includes a synchronous detector (3) for synchronously detecting the light emitted from the first optical modulator.
31, 332, 333); based on the detection result of the light emitted from the first optical modulator in a period other than the light pulse emission period by the synchronous detector, the second detector in a period other than the light pulse emission period. A first bias generator (334, 3) for generating a first bias signal to be added to the first main modulation signal so as to make the light emitted from one optical modulator zero.
35, 336, 337). In such a case, the first bias generator corrects the first bias signal and corrects the first main modulation signal based on the intensity of the emitted light accurately detected by the synchronous detector. It can be carried out.

In this case, the correction signal generator generates a second bias signal for generating a second bias signal for correcting the light intensity of the light emitted from the first light modulator to a predetermined intensity during a period other than the pulse train modulation period. Generator (350, 334,
335, 336, and 337). In such a case, the second bias generator sets the second bias generator based on the emission light intensity accurately detected by the synchronous detector.
Since the bias signal is generated, the intensity of the emitted light from the first optical modulator can be accurately set to a predetermined intensity.

Further, in the first light modulator of the present invention, the light modulator is connected in series with the first light modulator, and has a transmittance of approximately 0 to 1 or less according to the value of the second modulation signal. A second optical modulator (310 ′) that changes in a range; and a second pulse generator (320) that generates a second main modulation signal toward the second optical modulator may be further provided. . In such a case, the extinction ratio between the optical pulses can be further improved by generating the first main modulation signal and the second main modulation signal in synchronization with the first pulse generator and the second pulse generator. it can.

Here, the second modulation signal may be an electric signal, and the second optical modulator may be an electro-optical modulator. In such a case, light modulation can be performed by an electric signal that is easy to control and process.

In this case, the second modulation signal is a voltage signal, the second optical modulator is a second optical splitter that splits incident light into third light and fourth light; A third optical waveguide that guides the third light; a fourth optical waveguide that guides the fourth light and changes a refractive index according to an applied voltage value; A second electrode for applying a voltage based on the second modulation signal to at least a part thereof;
A configuration may be provided that includes a second multiplexer that multiplexes the third light via the waveguide and the fourth light via the fourth waveguide. In such a case, by adjusting the voltage applied to the second electrode and adjusting the difference in the optical path length between the third optical waveguide and the fourth optical waveguide, it is possible to modulate the light emitted from the second optical modulator. it can.

A second light modulator according to the present invention is a light modulator for modulating a pulse train of incident light and emitting the light, wherein the transmittance of the incident light is substantially 0 to 1 according to the value of the first modulation signal. A first optical modulator that changes in a range up to the following predetermined value; a first pulse generator that generates a first main modulation signal toward the first optical modulator; and a series with the first optical modulator. A second optical modulator connected and having a transmittance that varies in a range from approximately 0 to a predetermined value equal to or less than 1 according to the value of the second modulation signal; and a second main modulation signal toward the second optical modulator. And a second pulse generator that generates the following. According to this, the first
By generating the first main modulation signal and the second main modulation signal in synchronization with the pulse generator and the second pulse generator, pulse train modulation can be performed while improving the extinction ratio between optical pulses.

In the second light modulator of the present invention, the first light modulator
The modulation signal and the second modulation signal may be electrical signals, and the first light modulator and the second light modulator may be electro-optic modulators. In such a case, light modulation can be performed by an electric signal that is easy to control and process.

The light source device of the present invention comprises a light source (160A)
An optical modulator (160C) of the present invention for modulating a pulse train of the light emitted from the light source; and an optical fiber amplifier (168, 17) for amplifying the light emitted from the optical modulator.
1) A light source device comprising: According to this, since the light emitted from the light source is pulse train-modulated by the light modulator of the present invention and amplified by the optical fiber amplifier, the pulse power (energy) is large and the extinction ratio between light pulses is improved. Can occur. here,
In the case of using an optical modulator of the present invention, in which the intensity of light emitted from the first optical modulator is set to a predetermined intensity,
Further, it is possible to generate an optical pulse train having a uniform pulse power.

In the light source device according to the present invention, the light source may be a single-wavelength laser light source. In such a case, a pulse train of a single wavelength can be emitted.

Further, the light source device according to the present invention may further include a wavelength conversion device (163) including a non-linear optical crystal for receiving the light emitted from the optical fiber amplifier and performing harmonic conversion. . In such a case, even if the light source generates a long wavelength, as the light source device,
An ultraviolet light having a short wavelength suitable for an exposure apparatus can be generated.

Further, the light source device of the present invention further comprises a light blocking mechanism (17) provided downstream of the optical fiber amplifier and blocking outgoing light during periods other than the pulse train modulation period in the light modulator. It can be. In such a case, the light blocking mechanism blocks outgoing light during periods other than the pulse train modulation period, so that only the light pulse train can be emitted.

An exposure apparatus according to the present invention is an exposure apparatus for transferring a predetermined pattern onto a substrate by irradiating the substrate (W) with an exposure beam, wherein the exposure apparatus has a light blocking mechanism as a generator for the exposure beam. Light source device of the invention (16)
An exposure apparatus comprising: According to this, since the light source device of the present invention having the light blocking mechanism is provided as a device for generating an exposure beam, the exposure amount can be accurately controlled by controlling the number of pulses or controlling the pulse power. Therefore, a predetermined pattern can be transferred to the substrate with improved exposure accuracy.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a schematic configuration of an exposure apparatus 10 according to an embodiment including a light source device according to the present invention. The exposure apparatus 10 is a step-and-scan type scanning exposure apparatus.

The exposure apparatus 10 includes an illumination system including a light source device 16 and an illumination optical system 12, and a reticle R as a mask illuminated by exposure illumination light (hereinafter, referred to as "exposure light") IL from the illumination system. Stage RST for holding wafer W, projection optical system PL for projecting exposure light IL emitted from reticle R onto wafer W as a substrate, and Z tilt stage 5 as a substrate stage for holding wafer W
8 is provided with an XY stage 14 on which is mounted, and a control system for these.

The light source device 16 has a wavelength of 193, for example.
nm is (almost the same wavelength as the F ₂ laser beam) harmonic generator for outputting ultraviolet pulse light of ultraviolet pulse light, or wavelength 157nm of (almost the same wavelength as ArF excimer laser light). The light source device 16 includes a light source unit 16A including a laser light source as a light source, a laser control device 16B, a light amount control device 16C, and an optical shutter 17. The light source device 16 includes the illumination optical system 12, reticle stage RST, projection optical system PL, Z tilt stage 58, X
An exposure chamber (hereinafter, referred to as “chamber”) 11 in which temperature, pressure, humidity, and the like are adjusted with high accuracy, together with an exposure apparatus main body including a Y stage 14 and a main body column (not shown) on which these units are mounted. Is housed inside.

FIG. 2 is a block diagram showing the internal structure of the light source device 16 together with a main control device 50 for controlling the entire device.

As shown in FIG. 2, the light source section 16A
Is configured to include a pulse light generation unit 160 as a light generation unit, an optical amplification unit 161, a quarter-wave plate 162, a wavelength conversion unit 163, a beam monitoring mechanism 164, an absorption cell 165, and the like.

The pulse light generator 160 includes a laser light source 160A, optical couplers BS1 and BS2, an optical isolator 160B, an optical modulator 160C, and the like. The elements between the laser light source 160A and the wavelength converter 163 are optically connected by an optical fiber.

As the laser light source 160A, here, a single-wavelength oscillation laser, for example, an oscillation wavelength of 1.544
μm, continuous wave output (hereinafter referred to as “CW output”) 20 mW
InGaAsP and DFB semiconductor lasers are used. In the following, the laser light source 160A is appropriately referred to as “DF
B semiconductor laser 160A ".

Here, the DFB semiconductor laser means a Fabry-Perot resonator having low longitudinal mode selectivity,
A diffraction grating is built in a semiconductor laser, and is configured to oscillate in a single longitudinal mode under any circumstances. A distributed feedback (D)
FB) This is called a laser. Since such a laser basically oscillates in a single longitudinal mode, its oscillation spectrum line width can be suppressed to 0.01 pm or less.

The DFB semiconductor laser is usually provided on a heat sink, and these are housed in a housing. In the present embodiment, a temperature controller (for example, a Peltier element) is provided on a heat sink attached to the DFB semiconductor laser 160A, and the oscillation wavelength is controlled by the laser controller 16B controlling the temperature as described later. Are controllable (adjustable).

That is, the oscillation wavelength of the DFB semiconductor laser has a temperature dependency of about 0.1 nm / ° C. Therefore, for example, when the temperature of the DFB semiconductor laser is changed by 1 ° C.,
Since the wavelength of the fundamental wave (1544 nm) changes by 0.1 nm, the wavelength of the eighth harmonic (193 nm) changes by 0.0 nm.
The wavelength changes by 125 nm, and the wavelength changes by 0.01 nm at the tenth harmonic (157 nm).

In the exposure apparatus, it is sufficient if the wavelength of the exposure illumination light (pulse light) can be changed by about ± 20 pm with respect to the center wavelength. Therefore, the temperature of the DFB semiconductor laser 11 is set to about ± 1.6 °
In the case of the harmonic wave, it may be changed by about ± 2 ° C.

The laser light source 160A is a DFB
Not limited to semiconductor lasers such as semiconductor lasers, for example, ytterbium (Yb) -doped
A fiber laser or the like can also be used.

As the optical couplers BS1 and BS2,
Those having a transmittance of about 97% are used. Therefore, the laser beam from the DFB semiconductor laser 160A is split into two by the optical coupler BS1, about 97% of which travels toward the next-stage optical coupler BS2, and the remaining 3%
The degree is incident on the beam monitor mechanism 164. The laser light incident on the optical coupler BS2 is branched by the optical coupler BS2, and about 97% of the laser light travels toward the next-stage optical isolator 160B, and the remaining about 3% is absorbed by the absorption cell 1B.
65.

The beam monitor mechanism 164, absorption cell 165, etc. will be described later in more detail.

The optical isolator 160B allows only light in the direction from the optical coupler BS2 to the light modulator 160C to pass, and blocks light in the opposite direction from passing. The optical isolator 160B prevents a change in the oscillation mode of the DFB semiconductor laser 160A and the generation of noise due to the reflected light (return light).

The light modulator 160C is for converting the laser light (CW light (continuous light)) passing through the optical isolator 160B into pulse light. As shown in FIG. 3, the light modulation device 160C uses a single-electrode-type electro-optic effect in which a voltage is applied only to one side waveguide, and an optical modulator 310 according to a trigger signal V _TRG. a pulse generator 320 which towards the modulator 310 generates a pulse signal (pulse train signal) V _P, the correction signal generator 330 for generating a bias signal V _B for correcting the pulse signal V _P
And The optical modulator 310 employs an electro-optical effect (two-electrode type) using an electro-optic effect having an electrode structure with chirp correction so that the wavelength spread of the semiconductor laser output due to the chirp due to the change in the refractive index is reduced. Modulator).

The light modulator 160C includes the light modulator 3
Optical coupler 3 that branches a part of the outgoing light I _OUT from 10
45, a photodetector 341 that detects the light branched by the optical coupler 345 and converts the detected light into an electric signal (voltage signal: light detection signal) _VMON corresponding to the intensity thereof, and a light detection signal V
Track holder 342 that tracks or holds _MON
And the track holder 342 according to the trigger signal V _TRG.
A one-shot circuit 343 that generates a timing signal _VH for the track and hold operation, a switch 350 that opens and closes in response to an operation mode selection signal _VSEL indicating whether or not a pulse train modulation period, and a period that is not a pulse modulation period and a voltage generator V _X to set the voltage applied to the optical modulator 310 in. Further, the light modulator 160C
Is a resistive element R for organically coupling the above elements.
And capacitive elements C1 to C4. In the following description, the voltage value is also indicated by the signal name.

The optical modulator 310 includes an optical path section 311 for guiding incident light, an optical path 312 and an optical path 313 diverging from the optical path 311, an optical path 312 and an optical path 3.
13 and an optical path 314 that merges. Further, the optical modulator 310 has an electrode 315a and an electrode 315b for generating an electric field in at least a part of the optical path 313 and changing the refractive index by an electro-optic effect. Then, the electrode 315a with the bias signal V applied voltage signal V _C to the pulse signal V _P is corrected to _B is supplied, the electrode 315b is grounded.

In the optical modulator 310, the incident light is transmitted to the optical path 31.
1, the light is split into two light beams having the same light amount, and the two split light beams are respectively sent to the optical path 312 and the optical path 313.
To progress. Then, the two lights passing through the optical path 312 and the optical path 313 travel to the optical path 314 and are combined. That is, a branching filter is formed by a branching structure from the optical path 311 to the optical path 312 and the optical path 313, and the optical path 312 and the optical path 313 to the optical path 3
A multiplexer is constituted by a structure for merging with the signal.

The optical modulator 310 thus configured
In this case, the intensity of light that is multiplexed and emitted changes according to the optical path length difference between the optical path 312 and the optical path 313. For example,
If the optical path length difference between the optical path 312 and the optical path 313 is 0, the intensity I _{OUT of the} emitted light is the same as the intensity I _{IN of the} incident light, and the optical path length difference is の of the wavelength. In this case, the intensity of the emitted light becomes zero.

The optical path length changes according to the refractive index of the optical path. That is, as the refractive index increases, the optical path length increases, and as the refractive index decreases, the optical path length decreases. Utilizing this fact, the light modulator 160C adjusts the voltage V _C applied between the electrodes 315a and 315b to adjust the output light intensity I _OUT (to be exact, the ratio (I _OUT /
I _IN )).

The relationship between the ratio (I _OUT / I _IN ) and the applied voltage V _C in the optical modulator 310 according to the present embodiment is as shown in FIG. 4, and changes in a cosine function. here,
Applied voltage V _C ratio at the voltage value V _B0 is a voltage near 0V (I _OUT / I _IN) is 0, the applied voltage V _C is the voltage value (V
_T + _VB0 ) and the ratio (I _OUT / I _IN ) is 1. Therefore, the ratio (I _OUT / I _IN ) due to the change in the applied voltage V _C
Is expressed as: I _OUT / I _IN = 1−cos (V _C −V _B0 ) (1)

The correction signal generator 330 outputs the reference signal V
An oscillator 331 that outputs a _REF and a modulation signal V _MOD , and an integrator 33 that performs a product operation of an AC component of the reference signal V _REF and a zero-level signal V _Z output from the track holder 342.
2, passes through the low-frequency component of the multiplication result of the signal by the integrator 332, a low pass filter 333 outputs an error signal V _ERR, an integrator 335 for performing time integration calculation of the error signal V _ERR, by the integrator 335 An inverter 336 for inverting the sign of the integration result signal and an adder 337 for performing a sum operation on the output signal of the inverter 336 and the modulation signal V _MOD and outputting a bias signal V _B are provided.

Here, the reference signal V _REF and the modulation signal V _MOD
V _REF = V ₁ · sin (ω · t) (2) V _MOD = V ₂ · sin (ω · t + α) (3) Here, V ₁ , V ₂ , and α are constants, V ₁ is selected as a value at which the bias voltage V _B converges sufficiently quickly and reliably, and V ₂ is the final light of the light source unit 16. A value that is small enough to have no substantial effect on the output is selected. Α is the same as the reference signal V _REF when the modulation result of the emission light intensity I _OUT by the modulation signal V _MOD is input to the integrator 332 after passing through the photodetector 341, the track holder 342, and the like. Is chosen to be If the propagation of the modulation result by the modulation signal V _MOD is sufficiently short, the reference signal V _REF and the modulation signal V _MOD can be the same signal, that is, α = 0.

Incidentally, the above-mentioned emission light intensity I _OUT is 0
The voltage value V _B0 of the applied voltage V _C changes according to the temperature or the like. Therefore, initially the bias voltage V
Setting the _B to the voltage value V _B0 at that time, since over time the voltage value V _B0 is changed in a subsequent, sometimes light is emitted even between the optical pulses in the optical pulse train by the pulse train modulated. That is, there may be a case where the extinction ratio between the light pulses cannot be sufficiently maintained. The occurrence of such a situation appears as a control error when performing light amount control based on the light pulse interval and the light pulse power.

In the light modulation device of the present embodiment, such deterioration of the extinction ratio between light pulses is prevented as follows.

First, the oscillator 331 generates a modulation signal V _MOD . If this time is during the pulse train modulation period and not during the light pulse generation period, the AC component of the modulation signal V _MOD is input to the adder 337, and is added to the bias voltage substantially at the DC level at that time, and the addition is performed. result is a bias voltage V _B. Then, since it is not the generation period of the light pulse, the bias voltage V _B becomes the applied voltage V _{C as} it is, and the light passing through the light modulator 310 is slightly modulated at the angular velocity ω.

The result of the modulation is detected by the photodetector 341 and reflected on the monitor signal _VMON . FIG. 5A shows an example of the contribution of the modulation signal V _MOD to the monitor signal V _MON . As shown in FIG. 5, when the applied voltage V _C is the voltage value V _B0 and the modulation signal V _MOD is superimposed, the AC component which is the contribution of the modulation signal V _MOD to the monitor signal V _MON is | C (V _C ) · sin ω · t | (C
(V _C ): average value of applied voltage (hereinafter, also simply referred to as “applied voltage”), which is a positive constant determined by V _C. Also,
When the applied voltage V _C is what the modulation signal V _MOD at a high enough voltage value V _B1 than the voltage value V _B0 superimposed, modulated signal V _MOD
The AC component which is the contribution to the monitor signal V _MON by
(C (V _C ) · sin ω · t). Although not shown, if the modulation signal V _MOD is superimposed on the applied voltage V _C at a voltage value sufficiently lower than the voltage value V _B0 , the modulation signal V _MOD contributes to the monitor signal V _MON . The AC component is (−C (V _C ) · sin ω · t).

Since the track holder 342 is in a track state as described later when it is not during the period in which the light pulse is generated, the integrator 332 supplies the modulation signal V
An AC component of the monitor signal _VMON , which is a contribution of the _MOD to the monitor signal _VMON , is input. The product of the AC component of the monitor signal V _MON and the reference signal V _REF is calculated by the integrator 332, and the calculation result is filtered by the low-pass filter 333 to remove high-frequency components. In this way, a DC-level error signal V _ERR detected synchronously is obtained. FIG. 5B shows the relationship between the error signal V _ERR and the applied voltage V _C. As shown in FIG. 5, the range of the applied voltage V _C is if the _{((-V T / 2) +} V B0) is up to _{(V T / 2 + V B} 0) , the applied voltage than the voltage value V _B0 It becomes the error signal V _ERR is positive if the value V _C is high, whereas, the voltage value V _B0
When the applied voltage value V _C is lower than that, the error signal V _ERR becomes negative.

The thus obtained error signal V _ERR
Is input to the subtractor 334. During the pulse train modulation period, the input voltage V _D to the subtractor 334 is 0 as described later.
Therefore, the error signal V _ERR is directly input to the integrator 335 and further smoothed. Then, the integration result is input to the adder 337 sign is reversed by the inverter 336, a monitor signal V _MON is superimposed, is outputted as the bias signal V _B.

In the above feedback control, the error voltage V _{ERR is set} to 0, that is, if the applied voltage value V _C is larger than the voltage value V _B0 , the applied voltage value V _C
(I.e., the bias voltage V _B) acts to lower the, also, the applied voltage value V _C is smaller than the voltage value V _B0 acts to increase the applied voltage V _C. As a result, the bias voltage V _B is maintained very _close to the voltage value V _B0 that maximizes the extinction ratio between the light pulses at that time.

In the feedback control described above, it is assumed that the monitor signal V _MON is obtained as a result of monitoring the emitted light between the light pulses. Synchronous detection is performed regardless of whether it is between optical pulses. However, to reflect the coherent detection result in the light pulses emitted to the bias signal V _B would reduce the extinction ratio between the optical pulses. Therefore, in the optical modulation device 160C, at the timing shown in FIG. 6, the operation state of the track holder 342 is set to the hold state during the emission of the light pulse, the interval between the light pulses is set to the track state, and the monitor signal during the emission of the light pulse is changed. _Avoids V _MON synchronous detection.

That is, the light supplied from the light amount control device 16C is
Trigger signal V for generating an optical pulse _TRGRises,
Pulse signal V for generating optical pulse_PAt the same time
And the output signal V of the one-shot circuit 343_HIs rising
Thus, the operation state of the track holder 342 is held.
And As a result, the track holder 342
The voltage value immediately before the state is continuously output. this
Later, at the timing when the light pulse ends,
Output signal V on path 343_HFalls and again
The rudder 342 is set to the track state. This track state
At this point, it is already between light pulses. But
Thus, the monitor signal V during light pulse emission _MONSync
Detection is prevented.

In the light source device 16, the light emitted from the optical modulator 160C is amplified by an optical fiber amplifier. The amplification factor of the optical fiber amplifier is determined by the doping element in the excited doping fiber in the excited state. Is determined by the amount of Therefore, if the light intensity of the light emitted from the light modulator during the non-exposure period in which the pulse train modulation is not performed is set to 0, the excitation by the excitation light is sufficiently performed in the non-exposure period. It has become the maximum as an amplifier. On the other hand, after a while after the pulse train modulation is started for the exposure, the light pulse train is input one after another and consumes the exposure ability, so that the amplifying ability is lower than immediately after the pulse train modulation is started. . Therefore, even if the pulse powers of the light pulses emitted from the light modulation device 160C are equalized, the pulse powers of the light pulses emitted as the light source device 16 are not equalized. For this reason, in the light modulation device 160C, the average emitted light amount a · I _IN during the pulse train modulation period is obtained,
The light amount is always emitted during periods other than the pulse train modulation period.

That is, as shown in FIGS. 7A and 7B, the constant a for which the ratio (I _OUT / I _IN ) is obtained
After calculating the applied voltage value V _C (see FIG. 7A),
Obtaining an error voltage value V _X in the case of the applied voltage V _C. Then, in a period other than the pulse train modulation period, turns on the switch 350 of FIG. 3, and receives the voltage V _X to the subtractor 334. Also in this case, since the feedback control based on the synchronous detection described above operates so that the error voltage V _ERR becomes 0, the voltage (V _X + V _B0 ) is applied to the bias voltage V _B during a period other than the pulse train modulation period. It is supposed to be.

FIG. 8 shows a timing chart of such an operation. That is, as shown in FIG. 8, the selection signal V _SEL supplied from the main controller 50 rises, and when it is instructed that the period is the non-exposure period, the switch 350 is turned on in response thereto, applied voltage V _C is the voltage value V _X. As a result, the emitted light intensity I _{OU T}
Becomes a · I _IN . Then, the selection signal V _SEL supplied from the main controller 50 rises, and when it is instructed to be the exposure period, the switch 35 is responded accordingly.
0 is turned off, the applied voltage V _C is the voltage value V _B0. Thereafter, the operation in the pulse train modulation period described above is performed. Thus, the emission light I _OUT having the waveform shown in FIG. 9 is emitted from the light modulation device 160C.

For example, the DFB is
The laser light oscillated by the semiconductor laser 160A has a pulse width of 1 ns and a repetition frequency of 100 kHz (a pulse period of about
Assuming that the pulse light is modulated into a pulse light of 0 μs), as a result of this light modulation, the peak output of the pulse light output from the light modulator 160C is 20 mW, and the average output is 2 μW.
Here, it is assumed that there is no loss due to the insertion of the optical modulation device 160C. However, when the insertion loss is present, for example, when the loss is −3 dB, the peak output of the pulse light is 10 m.
W, the average output is 1 μW.

When the repetition frequency is set to about 100 kHz or more, a decrease in the amplification factor due to the influence of ASE (Amplified Spontaneous Emission) noise can be prevented in a fiber amplifier described later. Is desirable.

The optical amplifying section 161 includes an optical modulator 160
It amplifies the pulsed light from C, and here includes a plurality of fiber amplifiers. In FIG.
One example of the configuration of the optical amplifying unit 161 is an optical modulator 160
Shown with C.

As shown in FIG. 10, the optical amplifier 1
Reference numeral 61 denotes a delay unit 167 having a total of 128 channels 0 to 127, and fiber amplifiers 168 ₁ to 168 ₁ connected to respective output stages of a total of 128 channels from channel 0 to channel 127 of the delay unit 167.
168 ₁₂₈ and these fiber amplifiers 168 _{1 to} 168
Narrowband filter 169 in each of the _{128 1-169 128} and the optical isolator 170 _{1-170 128} a fiber amplifier 171 ₁ of the last stage connected via respective ～171 ₁₂₈
Etc. are provided. In this case, as is apparent from FIG. 10, the fiber amplifier 168 _n and the narrow band filter 16
9 _n , optical isolator 170 _n , and fiber amplifier 17
_{1 n (n = 1,2, ......} , 128) by each optical path _{172 n (n = 1,2, ......} , 128) is formed.

The above components of the optical amplifying unit 161 will be described in more detail. The delay unit 167 has a total of 128 channels and provides a predetermined delay time (here, 3 ns) to the output of each channel. belongs to. In the present embodiment, the delay unit 167 is a light modulator 160
Erbium (Er) -doped fiber amplifier (EDFA) for amplifying the pulse light output from C by 35 dB (3162 times), and the output of this EDFA to channel 0
And a splitter (a flat waveguide 1 × 4 splitter) which is a light splitting means for splitting into four outputs in parallel to four outputs, and four lights having different lengths connected to respective output terminals of channels 0 to 3 of the splitter. Fibers, four splitters (flat waveguide 1 × 32 splitters) that divide the outputs of these four optical fibers into channels 0 to 31 respectively, and channels 1 to 31 except for channel 0 of each splitter are connected to the respective fibers. And 31 (total 124) optical fibers having different lengths. Hereinafter, the channels 0 to 31 of each of the splitters (flat waveguide 1 × 32 splitter) are collectively called a block.

This will be described in more detail.
The pulse light output from A has a peak output of about 63 W and an average output of about 6.3 mW. This pulsed light is split into channels 0 to 3 by a splitter (flat waveguide 1 × 4 splitter).
And the output light of each channel is given a delay corresponding to the length of the four optical fibers. For example, in the present embodiment, the propagation speed of light in an optical fiber is 2
× 10 ⁸ m / s, and the splitter (plate waveguide 1
.Times.4, splitter) channels 0, 1, 2, and 3 have optical fibers of 0.1 m, 19.3 m, 38.5 m, and 57.7 m length respectively (hereinafter, referred to as "first delay fiber").
Is connected. In this case, the optical delay between adjacent channels at the exit of each first delay fiber is 96 ns.

The channels 1 to 31 of the four splitters (flat waveguide 1 × 32 splitters) are respectively provided with optical fibers (hereinafter referred to as “No. 2 delay fibers). As a result, a delay of 3 ns is given between adjacent channels in each block, and the output of channel 31 is 3 × 31 = 9 with respect to the output of channel 0 of each block.
A 3 ns delay is provided.

On the other hand, a delay of 96 ns is given between each of the first to fourth blocks by the first delay fiber as described above at the time of input of each block. Accordingly, the channel 0 output of the second block has a delay of 96 ns with respect to the channel 0 output of the first block, and the delay with the channel 31 of the first block is 3 ns. This is the same between the second and third blocks and the third and fourth blocks. As a result, a total output of 12
At the output terminals of the eight channels, pulse light having a delay of 3 ns between adjacent channels is obtained.

By the above branching and delay, a pulse light having a delay of 3 ns between adjacent channels can be obtained at the output terminals of a total of 128 channels. At this time, the optical pulse observed at each output terminal is an optical pulse. The same 100 kHz (pulse period of 10
μs). Therefore, looking at the entire laser beam generator, 9.62 after generating 128 pulses at 3 ns intervals.
The repetition that the next pulse train is generated at intervals of μs is performed at 100 kHz. That is, the total output is 12
8 × 100 × 10 ³ = 1.28 × 10 ⁷ pulses / sec.

In this embodiment, an example has been described in which the number of divisions is set to 128 and a short delay fiber is used. 9.62 μs between each pulse train
Although the interval of non-emission occurred, increase the number of divisions or lengthen the delay fiber to an appropriate length,
Alternatively, by using these in combination, it is possible to make the pulse intervals completely equal.

The fiber amplifier 168 _n (n = 1,
2,..., 128), the erbium (Er) -doped fiber whose mode field diameter (hereinafter referred to as “mode diameter”) of the optical fiber is 5 to 6 μm, similar to that used in normal communication. Amplifier (hereinafter referred to as "EDF
A "). This fiber amplifier 1
The output light from each channel of the delay unit 167 is amplified by 68 _n according to a predetermined amplification gain. The pump light source of the fiber amplifier 168 _n will be described later.

The narrow band filter 169 _n (n = 1,
2,..., 128) cut the ASE light generated in the fiber amplifier 168 _n , and
By transmitting the output wavelength of A (the wavelength width is about 1 pm or less), the wavelength width of the transmitted light is substantially narrowed. As a result, the ASE light is transmitted to the subsequent fiber amplifier 17.
1 _n to reduce the amplification gain of the laser light, or prevent scattering of the laser light due to propagation of ASE noise. Here, the narrow band filter 16
9 _n While it is preferred that the transmission wavelength width of about 1 pm, practically since the wavelength width of the ASE light is about several tens of nm, even using a narrow-band filter transmission wavelength width of about 100pm obtained at the present time The ASE light can be cut to such an extent that there is no problem.

In the present embodiment, as described later, D
Since the output wavelength of the FB semiconductor laser 160A may be positively changed, the transmission wavelength width (about the same as the variable width) corresponding to the variable width of the output wavelength (for example, about ± 20 pm in the exposure apparatus of the present embodiment). It is preferable to use a narrow band filter having the above. In a laser device applied to an exposure apparatus, the wavelength width is set to about 1 pm or less.

The optical isolator 170 _n (n = 1,
2,..., 128) correspond to the optical isolator 16 described above.
Like OB, it is for reducing the effect of the return light.

The fiber amplifier 171 _n (n = 1,
2, 128), the mode diameter of the optical fiber is smaller than that used in normal communication (5 to 6 μm) in order to avoid an increase in the spectrum width of the amplified light due to the nonlinear effect in the optical fiber. Wide, for example, 20-30μ
An EDFA with a large mode diameter of m is used. The fiber amplifier 171 _n is the same as the fiber amplifier 168 _n described above.
The optical output from each channel of the delay unit 167 that has been amplified by the above is further amplified. As an example, the average output of each channel in the delay unit 167 is 50 μW, and the average output of all channels is 6.3.
mW is increased by a total of 4 by the two-stage EDFAs 168 _n and 171 _n .
Assuming that amplification of 6 dB (40600 times) is performed, at the output end of the optical path 172 _n corresponding to each channel (the output end of the optical fiber constituting the fiber amplifier 171 _n ),
A peak output of 20 kW, a pulse width of 1 ns, a pulse repetition of 100 kHz, an average output of 2 W, and an average output of 256 W in all channels are obtained. The fiber amplifier 171
_{The n} excitation light sources and the like will be described later.

In the present embodiment, the output end of the optical path 172 _n corresponding to each channel in the delay section 167, that is, the output end of each optical fiber constituting the fiber amplifier 171 _n is bundled in a bundle. 173
(See FIG. 12). At this time, since the clad diameter of each optical fiber is about 125 μm,
The diameter of the bundle at the output end of 128 bundles is about 2 mm
It can be: In this embodiment, the fiber bundle 173 is formed by using the output end of EDFA171 _n of the last stage as it is, the final stage EDFA17
It is also possible to couple an undoped optical fiber to 1 _n and form a bundle-fiber at its output end.

The connection between the previous-stage fiber amplifier 167 _n having a standard mode diameter and the last-stage fiber amplifier 171 _n having a large mode diameter is made by using an optical fiber whose mode diameter increases in a tapered shape. Is being done.

Next, an excitation light source and the like of each fiber amplifier will be described with reference to FIG. FIG. 11 shows a fiber amplifier constituting the optical amplifying unit 161 and its peripheral parts.
It is schematically shown together with a part of the wavelength converter 163.

In FIG. 11, a semiconductor laser 178 for excitation is fiber-coupled to a first-stage fiber amplifier 168 _n, and the output of the semiconductor laser 178 is supplied to a wavelength division multiplexer (Wavelength Division Multiplexer).
(iplexer: WDM) 179 to be incident on the doped fiber for the fiber amplifier, whereby the doped fiber is excited.

On the other hand, a fiber amplifier 17 having a large mode diameter
In 1 _n, a semiconductor laser 174 as an excitation light source for exciting a large fiber amplifier for doped fiber mode diameter of the fiber coupled to large mode diameter fiber to match the diameter of a fiber amplifier for doped fiber The light emitted from the semiconductor laser 174 is transmitted to the WDM 176.
Is used to enter the doped fiber for an optical amplifier to excite the doped fiber.

The laser light amplified by the large mode diameter fiber (fiber amplifier) 171 _n is
, Where the wavelength is converted to ultraviolet laser light. The configuration and the like of the wavelength converter 163 will be described later.

Large mode diameter fiber (fiber amplifier) 1
The laser light (signal) to be amplified propagating through 71 _n is
It is desirable that the fundamental mode is mainly used, and this can be realized by selectively exciting the fundamental mode mainly in a single mode or a multimode fiber having a low mode order.

In the present embodiment, four high-power semiconductor lasers coupled to a large-mode diameter fiber are coupled to four fibers from the front and four from the rear. Here, in order to efficiently couple the semiconductor laser light for excitation to the doped fiber for optical amplification, an optical fiber having a double clad structure having a double clad structure is used as the doped fiber for optical amplification. desirable. At this time, the semiconductor laser light for excitation is introduced into the inner clad of the double clad by the WDM 176.

The semiconductor lasers 178 and 174 are controlled by a light quantity control device 16C.

[0091] Further, in the present embodiment, the fiber amplifier 168 _n, 1 as optical fibers constituting the optical path 172 _n
Since 71 _n is provided, the difference between the gains of the fiber amplifiers causes variations in the optical output of each channel. For this reason, in the present embodiment, the fiber amplifier (1
68 _n , 171 _n ) are partially branched, and photoelectric conversion elements 180, 181 provided at the respective branch ends.
Respectively, so that they are photoelectrically converted. The output signals of these photoelectric conversion elements 180 and 181 are supplied to the light quantity control device 16C.

In the light amount control device 16C, each of the pumping semiconductor lasers (178, 178) is controlled so that the light output from each fiber amplifier becomes constant (ie, balanced) at each amplification stage.
The drive current of 174) is feedback-controlled.

Further, in this embodiment, as shown in FIG. 11, the light split by the beam splitter in the middle of the wavelength converter 163 is photoelectrically converted by the photoelectric conversion element 182, and the output signal of the photoelectric conversion element 182 is output. Is supplied to the light amount control device 16C. The light amount control device 16C monitors the light intensity in the wavelength conversion unit 163 based on the output signal of the photoelectric conversion element 182, and controls the excitation semiconductor laser so that the light output from the wavelength conversion unit 163 becomes a predetermined light output. At least one of the drive currents 178 and 174 is feedback-controlled.

With such a configuration, the amplification factors of the fiber amplifiers of the respective channels are made constant for each amplification stage. Strength is obtained. Further, by monitoring the light intensity in the wavelength conversion unit 163, a predetermined predetermined light intensity is fed back to each amplification stage, and a desired ultraviolet light output can be stably obtained.

The optical amplifying unit 16 constructed as described above
From 1 (the output end of each optical fiber forming the bundle-fiber 173), all the pulsed lights are output in a state of being circularly polarized. These circularly polarized pulse lights are converted by the quarter-wave plate 162 (see FIG. 2) into linearly polarized lights, all of which have the same polarization direction.
3 is incident.

The wavelength converter 163 includes a plurality of nonlinear optical crystals, and the amplified pulse light (wavelength 1.54
(4 μm light) is wavelength-converted into its 8th harmonic or 10th harmonic, and the same output wavelength (19) as that of the ArF excimer laser.
3 nm) or the same output wavelength as the F ₂ laser (157 n
m) pulsed ultraviolet light is generated.

FIGS. 12A and 12B show examples of the configuration of the wavelength converter 163. FIG. Here, a specific example of the wavelength conversion unit 163 will be described based on these drawings.

FIG. 12A shows the fiber bundle 17.
The wavelength of the fundamental wave having a wavelength of 1.544 μm emitted from the output end of No. 3 is converted into an eighth harmonic (harmonic wave) using a nonlinear optical crystal, and the wavelength is converted to 193 which is the same wavelength as that of the ArF excimer laser.
1 shows a configuration example for generating ultraviolet light of nm. FIG.
(B) shows that a fundamental wave having a wavelength of 1.57 μm emitted from the output end of the fiber bundle 173 is generated as a tenth harmonic using a nonlinear optical crystal, and an ultraviolet ray of 157 nm, which is the same wavelength as the F ₂ laser, is generated. An example of a configuration for generating light is shown.

In the wavelength converter shown in FIG. 12A, the fundamental wave (wavelength: 1.544 μm) → the second harmonic wave (wavelength: 772 nm) →
Third harmonic (wavelength 515 nm) → fourth harmonic (wavelength 386 nm)
→ 7th harmonic (wavelength 221 nm) → 8th harmonic (wavelength 193n)
The wavelength conversion is performed in the order of m).

More specifically, the wavelength outputted from the output end of the fiber bundle 173 is 1.544 μm.
The fundamental wave of (frequency ω) is the first-stage nonlinear optical crystal 53
3 is incident. When the fundamental wave passes through the nonlinear optical crystal 533, the second harmonic generation causes the fundamental wave to have a frequency ω of 2
Double, ie, frequency 2ω (wavelength is ２ of 772 nm)
Is generated.

As the first-stage nonlinear optical crystal 533, a LiB ₃ O ₅ (LBO) crystal is used, and a fundamental wave of 2
A method by temperature control of LBO crystal for phase matching for wavelength conversion to harmonic, NCPM (Non-Critical Phase Match)
ing) is used. The NCPM enables high-efficiency conversion to a second harmonic wave because an angle shift (Walk-off) between the fundamental wave and the second harmonic in the nonlinear optical crystal does not occur. This is advantageous because the beam is not deformed by the walk-off. In the case of FIG. 6A,
The above-described linear polarization by the quarter-wave plate 162 is performed so that the nonlinear optical crystal 533 has a polarization direction in which the second harmonic is generated most efficiently. The setting of the polarization direction of the linearly polarized light is performed by adjusting the direction of the optical axis of the 波長 wavelength plate 162.

The fundamental wave transmitted without wavelength conversion by the nonlinear optical crystal 533 and the second harmonic wave generated by the wavelength conversion are given a half wavelength and a one wavelength delay by the next-stage wavelength plate 534, respectively. Only the fundamental wave rotates its polarization direction by 90 degrees,
The light is incident on the nonlinear optical crystal 536 of the stage. An LBO crystal is used as the second-stage nonlinear optical crystal 536, and the LBO crystal is the first-stage nonlinear optical crystal (LBO crystal).
Crystal) 533 is used in NCPM at a different temperature.
In this nonlinear optical crystal 536, a third harmonic (wavelength: 515 nm) is generated from the second harmonic generated in the first-stage nonlinear optical crystal 533 and the fundamental wave transmitted through the nonlinear optical crystal 533 without wavelength conversion. Get)

Next, the 3D obtained by the nonlinear optical crystal 536
The harmonic, the fundamental wave and the second harmonic transmitted through the nonlinear optical crystal 536 without wavelength conversion are separated by a dichroic mirror 537, and the third harmonic reflected here is collected by a condenser lens 540 and a dichroic.・ Mirror 543
And enters the fourth-stage nonlinear optical crystal 545. On the other hand, the fundamental wave and the second harmonic transmitted through the dichroic mirror 537 pass through the condenser lens 538 and enter the third-stage nonlinear optical crystal 539.

As the third-stage nonlinear optical crystal 539, L
A BO crystal is used, and the fundamental wave is
While passing through the BO crystal, the second harmonic is 2
It is converted into a fourth harmonic (wavelength 386 nm) by generation of the second harmonic. The fourth harmonic obtained by the nonlinear optical crystal 539 and the fundamental wave transmitted therethrough are separated by the dichroic mirror 541, and the fundamental wave transmitted therethrough is collected by the condenser lens 54.
4 and is reflected by a dichroic mirror 546 to enter a fifth-stage nonlinear optical crystal 548. On the other hand, the fourth harmonic reflected by the dichroic mirror 541 reaches the dichroic mirror 543 through the condensing lens 542, where it is coaxially combined with the third harmonic reflected by the dichroic mirror 537 to form a fourth stage. The light enters the nonlinear optical crystal 545 of the eye.

The fourth-stage nonlinear optical crystal 545 includes:
β-BaB ₂ O ₄ (BBO) crystal is used,
Seventh harmonic (wavelength 221 nm) by sum frequency generation from harmonics
Get. The seventh harmonic obtained by the non-linear optical crystal 545 passes through the condenser lens 547 and is coaxially synthesized by the dichroic mirror 546 with the fundamental wave transmitted through the dichroic mirror 541.
8 is incident.

As the fifth-stage nonlinear optical crystal 548, LB
An O crystal is used, and an eighth harmonic (wavelength 193 nm) is obtained from the fundamental wave and the seventh harmonic by generating a sum frequency. In the above configuration, instead of the seventh harmonic generation BBO crystal 545 and the eighth harmonic generation LBO crystal 548, CsLiB ₆ O ₁₀ (CL
BO) crystal or Li ₂ B ₄ O ₇ (LB4) crystal can also be used.

In the configuration example of FIG. 12A, since the third harmonic and the fourth harmonic enter the fourth-stage nonlinear optical crystal 545 through optical paths different from each other, a lens for condensing the third harmonic. The 540 and the lens 542 that collects the fourth harmonic can be placed in separate optical paths. Third-stage nonlinear optical crystal 539
The cross-sectional shape of the fourth harmonic generated in the above is oval due to the walk-off phenomenon. Therefore, in order to obtain good conversion efficiency in the fourth-stage nonlinear optical crystal 545, it is desirable to perform beam shaping of its fourth harmonic. In this case, since the condenser lenses 540 and 542 are arranged in separate optical paths,
For example, a cylindrical lens pair can be used as the lens 542, and beam shaping of the fourth harmonic can be easily performed. Therefore, the fourth-stage nonlinear optical crystal (B
(BO crystal) 545, and the conversion efficiency can be increased.

Further, the lens 544 for condensing the fundamental wave incident on the fifth-stage nonlinear optical crystal 548 and the lens 547 for condensing the seventh harmonic can be placed on different optical paths. The seventh harmonic generated by the fourth-stage nonlinear optical crystal 545 has an elliptical cross-sectional shape due to the walk-off phenomenon. Therefore, in order to obtain good conversion efficiency in the fifth-stage nonlinear optical crystal 548, it is preferable to perform beam shaping of the seventh harmonic thereof. In the present embodiment, the condenser lens 544,
Since the 547s can be arranged in separate optical paths, for example, a pair of cylindrical lenses can be used as the lens 547, and the beam shaping of the seventh harmonic can be easily performed. Therefore, the fifth-stage nonlinear optical crystal (LBO)
It is possible to make the overlap with the fundamental wave at (crystal) 548 good and increase the conversion efficiency.

The second-stage nonlinear optical crystals 536 and 4
The configuration between the non-linear optical crystal 545 of the stage and FIG.
It is not limited to (A), but a nonlinear optical crystal 536
And a fourth harmonic obtained by wavelength-converting the second harmonic generated by the dichroic mirror 537 and reflected by the dichroic mirror 537 and the second harmonic generated by the non-linear optical crystal 536 through the dichroic mirror 537. Any configuration may be used as long as the two optical path lengths between the two nonlinear optical crystals 536 and 545 are equal so that the light beams enter the nonlinear optical crystal 545 at the same time. This is because the third-stage nonlinear optical crystal 539 and the fifth-stage nonlinear optical crystal 5
The same applies to the case of 48.

In the wavelength converter shown in FIG. 12B, the fundamental wave (wavelength 1.57 μm) → the second harmonic wave (wavelength 785 nm) → 4
Harmonic (wavelength 392.5 nm) → 8th harmonic (wavelength 196.2)
The wavelength is converted in the order of 5 nm) to 10th harmonic (wavelength: 157 nm). In this configuration example, in each wavelength conversion stage from the second harmonic generation to the eighth harmonic generation, the second harmonic generation of the wavelength incident on each wavelength conversion stage is performed.

In this configuration example, as a nonlinear optical crystal used for wavelength conversion, an LBO crystal is used as a nonlinear optical crystal 602 for generating a second harmonic by generating a second harmonic from a fundamental wave. An LBO crystal is used as the nonlinear optical crystal 604 that generates the fourth harmonic by generating the second harmonic. Further, Sr ₂ Be ₂ B ₂ O ₇ is applied to the nonlinear optical crystal 609 for generating the eighth harmonic by the second harmonic generation from the fourth harmonic.
An (SBBO) crystal is used, and an SBBO crystal is used as the nonlinear optical crystal 611 that generates a tenth harmonic (wavelength: 157 nm) by sum frequency generation from the second harmonic and the eighth harmonic.

The second harmonic generated from the nonlinear optical crystal 602 passes through the condenser lens 603 and passes through the nonlinear optical crystal 6.
In this case, the nonlinear optical crystal 604 generates the above-described fourth harmonic and a second harmonic whose wavelength is not converted. Next, the second harmonic transmitted through the dichroic mirror 605 passes through the condenser lens 606 and the dichroic mirror 60
The light is reflected by 7 and enters the nonlinear optical crystal 611. On the other hand, the fourth harmonic reflected by the dichroic mirror 605 is incident on the nonlinear optical crystal 609 through the condenser lens 608, and the eighth harmonic generated here is collected by the condenser lens 610,
Then, the light enters the nonlinear optical crystal 611 through the dichroic mirror 607. Further, the nonlinear optical crystal 611
Generates a 10th harmonic (wavelength: 157 nm) from the second harmonic and the eighth harmonic that are coaxially synthesized by the dichroic mirror 607 by generating a sum frequency.

By the way, in the present configuration example, the second harmonic and the fourth harmonic generated from the second-stage nonlinear optical crystal 604 are branched by the dichroic mirror 605, so that the second harmonic and the fourth harmonic are transmitted therethrough. The eighth harmonic obtained by wavelength-converting the wave by the nonlinear optical crystal 609 is configured to enter the fourth-stage nonlinear optical crystal 611 through different optical paths, but without using the dichroic mirrors 605 and 607. Four nonlinear optical crystals 602, 604, 609, 611
May be arranged on the same optical axis.

However, in this configuration example, the fourth harmonic generated in the second-stage nonlinear optical crystal 604 has an oval cross section due to the Walk-off phenomenon. For this reason, in order to obtain good conversion efficiency in the fourth-stage nonlinear optical crystal 611 using this beam as an input, the beam shape of the fourth harmonic wave as an incident beam is shaped to improve the overlap with the second harmonic wave. Is desirable. In the present configuration example, the condenser lenses 606 and 608 can be arranged in separate optical paths.
As 08, a cylindrical lens can be used, and beam shaping of the fourth harmonic can be easily performed.
For this reason, it is possible to make the overlap with the second harmonic in the fourth-stage nonlinear optical crystal 611 good, and to increase the conversion efficiency.

The wavelength converters shown in FIGS. 12A and 12B are merely examples, and the configuration of the wavelength converter of the present invention is not limited to this.

Returning to FIG. 2, the beam monitor mechanism 164
Here is the Fabry-Perot etalon
etalon: hereinafter, also referred to as an “etalon element” and an energy monitor (not shown) including a photoelectric conversion element such as a photodiode. Light incident on the etalon element constituting the beam monitor mechanism 164 is
The light is transmitted at a transmittance corresponding to the frequency difference between the resonance frequency of the etalon element and the frequency of the incident light, and an output signal of a photodiode or the like that detects the transmitted light intensity at this time is supplied to the laser control device 16B. The laser control device 16B performs predetermined signal processing on this signal to obtain information on the optical characteristics of the incident light with respect to the beam monitor mechanism 164, specifically, the etalon element (specifically, the center wavelength and the wavelength width of the incident light ( The information on the optical characteristics is obtained in real time by the main controller 5.
0 is notified.

The frequency characteristics of the transmitted light intensity generated by the etalon element are affected by the temperature and pressure of the atmosphere, and the resonance frequency (resonance wavelength) is temperature-dependent. Therefore, in order to accurately control the center wavelength and the spectral half width of the laser beam oscillated from the laser light source 160A based on the detection result of the etalon element, it is necessary to examine the temperature dependence of the resonance wavelength. is important. In the present embodiment, the temperature dependence of the resonance wavelength is measured in advance, and the measurement result is stored as a temperature dependence map in a memory 51 (see FIG. 1) as a storage device provided in the main control device 50. . Then, the main controller 50 performs, for example, when the absolute wavelength calibration of the beam monitor mechanism 164 is performed.
In order to make the resonance wavelength (detection reference wavelength) at which the transmittance of the etalon element becomes the maximum exactly coincide with the set wavelength, an instruction is given to the laser control device 16B so that the temperature of the etalon element in the beam monitor mechanism 164 is reduced. They are actively controlled.

The output of the energy monitor constituting the beam monitor mechanism 164 is supplied to the main controller 50. The main controller 50 detects the energy power of the laser beam based on the output of the energy monitor, and The amount of the laser light oscillated by the DFB semiconductor laser 160A via the control device 16B is controlled as necessary,
For example, the semiconductor laser 160A is turned off. However, in the present embodiment, as will be described later, the normal light amount control (exposure amount control) is mainly performed by the light amount control device 16C to control the peak power or frequency of the output pulse light of the light modulation device 160C, or to control the light amplification unit. 161 is performed by on / off control of the output light of each fiber amplifier.
When the energy power of the laser light fluctuates greatly for some reason, main controller 50 controls laser controller 16B as described above.

The absorption cell 165 performs absolute wavelength calibration of the oscillation wavelength of the DFB semiconductor laser 160A,
That is, it is an absolute wavelength source for absolute wavelength calibration of the beam monitor mechanism 164. In this embodiment,
Since the absorption cell 165 uses a DFB semiconductor laser 160A having an oscillation wavelength of 1.544 μm as a laser light source, an isotope of acetylene having an absorption line densely in a wavelength band near this wavelength is used. .

As will be described later, as the light for monitoring the wavelength of the laser light, together with or instead of the fundamental wave, the intermediate wave (second harmonic wave, third wave) of the above-described wavelength converter 163 is used.
In the case of selecting a harmonic wave, a fourth harmonic wave or the like, or light after wavelength conversion, an absorption cell in which absorption lines exist densely in a wavelength band such as an intermediate wave may be used. For example, when the third harmonic is selected as the wavelength monitoring light, the wavelength 503 is selected.
An iodine molecule having an absorption line densely in the vicinity of nm to 530 nm may be used as an absorption cell, an appropriate absorption line of the iodine molecule may be selected, and the wavelength may be used as an absolute wavelength.

The absolute wavelength source is not limited to the absorption cell, but may be an absolute wavelength light source.

The laser control device 16B detects the center wavelength and the wavelength width (spectral half width) of the laser beam based on the output of the beam monitoring mechanism 164 so that the center wavelength becomes a desired value (set wavelength). DFB semiconductor laser 16
The temperature control (and current control) of 0 A is performed by feedback control. In this embodiment, the DFB semiconductor laser 160
The temperature of A can be controlled in 0.001 ° C. units.

The laser control device 16B operates in response to an instruction from the main control device 50,
Switching between a pulse output of 60 A and continuous output, control of an output interval and a pulse width at the time of the pulse output, and control of the DF so as to compensate for output fluctuation of the pulsed light.
The oscillation of the B semiconductor laser 160A is controlled.

As described above, in the laser control device 16B, the oscillation wavelength is stabilized and controlled to a constant wavelength, or the output wavelength is finely adjusted. Conversely, the laser controller 16B responds to an instruction from the main controller 50 to
The output wavelength may be adjusted by positively changing the oscillation wavelength of the B semiconductor laser 160A.

For example, according to the former, the occurrence of the aberration (imaging characteristics) of the projection optical system PL due to the wavelength fluctuation or the fluctuation thereof is prevented, and the image characteristics (optical characteristics such as image quality) during the pattern transfer are prevented. Will not change.

According to the latter, an altitude difference and a pressure difference between a manufacturing site where an exposure apparatus is assembled and adjusted and an installation place (delivery destination) of the exposure apparatus, and a difference in environment (atmosphere in a clean room) and the like. Therefore, fluctuations in the imaging characteristics (such as aberration) of the projection optical system PL that occur in accordance with the above conditions can be offset, and the time required to start up the exposure apparatus at the delivery destination can be reduced. Furthermore, according to the latter, during the operation of the exposure apparatus, it is possible to cancel the variation of the aberration, projection magnification, and focal position of the projection optical system PL caused by the irradiation of the exposure illumination light and the change in the atmospheric pressure. Thus, the pattern image can always be transferred onto the substrate in the best image forming state.

As described above, the light quantity control device 16C includes the fiber amplifiers 168 _n , 17
Each excitation semiconductor laser (178, 17) is based on the output of the photoelectric conversion element 180, 181, which detects the 1 _n light output.
4) feedback control of the drive current to stabilize the amplification factor of the fiber amplifier of each channel for each amplification stage, and a photoelectric conversion element for detecting light split by the beam splitter in the wavelength conversion section 163 182, based on the output signal of the semiconductor laser 182,
A feedback control of at least one of the drive currents to feed back a predetermined light intensity to each amplification stage to stabilize a desired ultraviolet light output.

Further, in the present embodiment, the light amount control device 16
C also has the following functions.

That is, in response to an instruction from the main controller 50, the light amount controller 16C outputs the output of the fiber of each channel constituting the fiber bundle 173,
That is, a function of controlling the average light output of the entire bundle by individually turning on and off the output of each optical path 172 _n (hereinafter, referred to as a “first function” for convenience) and a main controller 50 The light modulation device 1
By controlling the frequency of the pulsed light output from the 60C, the average light output (output energy) of each channel of the optical amplifying unit 161 per unit time, that is, the output light from each optical path 172 _n per unit time is output. A function for controlling the intensity (hereinafter, referred to as a “second function” for convenience) and an optical modulation device 1 according to an instruction from main controller 50.
By controlling the peak power of the pulsed light output from the 60C, the average light output (output energy) of each channel of the optical amplifier 161 per unit time, that is, the output light from each optical path 172 _n per unit time. (Hereinafter, referred to as “third function” for convenience).

In the present embodiment, upon exposure to be described later,
The first function of the light quantity control device 16C performs coarse adjustment of the exposure amount, and fine adjustment of the exposure amount is performed using the second and third functions.

The light quantity control device 16C also controls the start and stop of pulse output based on an instruction from the main control device 50.

As described above, under the control of the main controller 50, the light output from the light source section 16A passes through the optical shutter 17 that transmits light only during the exposure period, that is, during the pulse train modulation period in the light modulator 160C. Is injected.
Thus, only the light pulse train is emitted from the light source device 16 during the exposure period.

Returning to FIG. 1, the illumination optical system 12 includes a beam shaping optical system 18, a fly-eye lens system 22 as an optical integrator (homogenizer), an illumination system aperture stop plate 24, a beam splitter 26, and a first relay lens 28A. , A second relay lens 28B, a fixed reticle blind 30A, a movable reticle blind 30B, a mirror M for bending the optical path, a condenser lens 32, and the like.

The beam shaping optical system 18 includes the light source device 1
The cross-sectional shape of the ultraviolet light (hereinafter referred to as “laser beam”) LB generated by the wavelength conversion of the wavelength conversion unit 163 of FIG. 6 is converted to the fly-eye lens system 22 provided behind the optical path of the laser beam LB. The beam is shaped so as to be incident efficiently, and includes, for example, a cylinder lens and a beam expander (both not shown).

The fly-eye lens system 22 is arranged on the optical path of the laser beam LB emitted from the beam shaping optical system 18, and is a surface light source comprising a large number of light source images for illuminating the reticle R with a uniform illuminance distribution. That is, a secondary light source is formed.
The laser beam emitted from the secondary light source is also referred to as “exposure light IL” in this specification.

In the vicinity of the exit surface of the fly-eye lens system 22, an illumination system aperture stop plate 24 made of a disc-like member is arranged. The illumination system aperture stop plate 24 includes, at equal angular intervals, an aperture stop composed of, for example, a normal circular aperture, an aperture stop composed of a small circular aperture, for reducing the σ value, which is a coherence factor, and a ring for annular illumination. A band-shaped aperture stop, a modified aperture stop having a plurality of apertures eccentrically arranged for the modified light source method (only two types of aperture stops are shown in FIG. 1) and the like are arranged. . The illumination system aperture stop plate 24 is configured to be rotated by a driving device 40 such as a motor controlled by a main control device 50, so that one of the aperture stops responds to the exposure light IL according to the reticle pattern. It is selectively set on the optical path.

Exposure light IL emitted from illumination system aperture stop plate 24
A beam splitter 26 having a small reflectance and a large transmittance is disposed on the optical path of the first relay lens 28A, and the first relay lens 28A and the second relay A relay optical system including a lens 28B is provided.

The fixed reticle blind 30A is arranged on a plane slightly defocused from a plane conjugate to the pattern plane of the reticle R, and has a rectangular opening defining an illumination area 42R on the reticle R. Further, a movable reticle blind 30B having an opening whose position and width in the scanning direction are variable near the fixed reticle blind 30A.
Is arranged, and at the start and end of the scanning exposure, the illumination area 42R is further restricted via the movable reticle blind 30B, so that exposure of an unnecessary portion is prevented.

A bending mirror M for reflecting the exposure light IL passing through the second relay lens 28B toward the reticle R is disposed on the optical path of the exposure light IL behind the second relay lens 28B constituting the relay optical system. And this mirror M
A condenser lens 32 is arranged on the optical path of the rear exposure light IL.

Further, an integrator sensor 46 and a reflected light monitor 4 are provided on one of the optical paths which are bent vertically by the beam splitter 26 in the illumination optical system 12 and on the other optical path.
7 are arranged respectively. The integrator sensor 46 and the reflected light monitor 47 have a high sensitivity in the deep ultraviolet region and the vacuum ultraviolet region, and have a high response frequency for detecting the pulse light emission of the light source device 16.
Type photodiodes are used. Note that a semiconductor light receiving element having a GaN-based crystal can be used as the integrator sensor 46 and the reflected light monitor 47.

In the above configuration, the entrance surface of the fly-eye lens system 22, the arrangement surface of the movable reticle blind 30B, and the pattern surface of the reticle R are optically set to be conjugate with each other. The light source surface and the Fourier transform surface (exit pupil surface) of the projection optical system PL are optically set to be conjugate to each other to form a Koehler illumination system.

The operation of the illumination system 12 configured as described above will be briefly described. A laser beam LB pulse-emitted from the light source device 16 enters a beam shaping optical system 18 where a rear fly-eye is formed. After its cross-sectional shape is shaped so as to efficiently enter the lens system 22, the light enters the fly-eye lens system 22. As a result, a secondary light source is formed on the exit-side focal plane of the fly-eye lens system 22 (pupil plane of the illumination optical system 12). The exposure light IL emitted from the secondary light source passes through one of the aperture stops on the illumination system aperture stop plate 24, and then reaches a beam splitter 26 having a large transmittance and a small reflectance. The exposure light IL transmitted through the beam splitter 26 passes through the first relay lens 28A, passes through the rectangular opening of the fixed reticle blind 30A and the movable reticle blind 30B, passes through the second relay lens 28B, and is mirrored by the mirror M. After the optical path is bent vertically downward, the rectangular illumination area 42R on the reticle R held on the reticle stage RST is illuminated with a uniform illuminance distribution via the condenser lens 32.

On the other hand, the exposure light IL reflected by the beam splitter 26 is received by an integrator sensor 46 via a condenser lens 44, and a photoelectric conversion signal of the integrator sensor 46 is converted into a peak hold circuit (not shown) and an A / D converter.
It is supplied to the main controller 50 as an output DS (digit / pulse) via a converter. The correlation coefficient between the output DS of the integrator sensor 46 and the illuminance (exposure amount) of the exposure light IL on the surface of the wafer W is stored in a memory 51 provided as a storage device provided in the main controller 50. ing.

The illuminated area 42R on the reticle R, and the reflected light beam reflected on the pattern surface of the reticle (the lower surface in FIG. 1) passes through the condenser lens 32 and the relay optical system in the opposite direction to the front, and The light is reflected by the beam splitter 26 and received by a reflected light monitor 47 via a condenser lens 48. When the Z tilt stage 58 is below the projection optical system PL, the exposure light IL transmitted through the pattern surface of the reticle is applied to the projection optical system PL and the surface of the wafer W (or the surface of a reference mark plate FM described later). The reflected light flux passes through the projection optical system PL, the reticle R, the condenser lens 32, and the relay optical system sequentially in the opposite direction to the front, is reflected by the beam splitter 26, and is reflected by the condensing lens 48. The light is received by the monitor 47. Each optical element disposed between the beam splitter 26 and the wafer W has an anti-reflection film formed on the surface thereof, but the exposure light IL is slightly reflected on the surface, and the reflected light is also reflected light. The light is received by the monitor 47. The photoelectric conversion signal of the reflected light monitor 47 is supplied to the main controller 50 via a peak hold circuit and an A / D converter (not shown). In this embodiment, the reflected light monitor 47 is mainly used for measuring the reflectance of the wafer W and the like. Note that the reflected light monitor 47 may be used for the preliminary measurement of the transmittance of the reticle R.

As the fly-eye lens system 22, for example, JP-A-1-235289 (corresponding US Pat. No. 5,307,207) and JP-A-7-142354 (corresponding US Pat. No. 5,534,970) ) May be used to form a Koehler illumination system.

Further, together with the fly-eye lens system 22,
A diffractive optical element may be used. When such a diffractive optical element is used, the light source device 16 and the illumination optical system 12 may be connected via a diffractive optical element. That is, a diffractive optical element in which a diffractive element is formed corresponding to each fiber of the fiber bundle 173 is provided in the beam shaping optical system 18, and the laser beam output from each fiber is diffracted, and the incident light of the fly-eye lens system 22 is incident. You may make it superimpose on a surface. In this example, the output end of the fiber bundle 173 may be arranged on the pupil plane of the illumination optical system.
(Thinning), the intensity distribution on the pupil plane (that is, the shape and size of the secondary light source) changes, and the shape and size may be different from the optimum shape and size for the reticle pattern. Therefore, it is preferable that the laser beam from each fiber is superimposed on the pupil plane of the illumination optical system or the entrance plane of the optical integrator using the above-described diffractive optical element or the like.

In any case, in the present embodiment, even if the distribution of the light output portion of the fiber bundle 173 changes due to the first function of the light amount control device 16C described above, the pattern surface of the reticle R can be changed. The uniformity of the illuminance distribution can be sufficiently ensured on both the (object surface) and the surface (image surface) of the wafer W.

A reticle R is mounted on the reticle stage RST, and is held by suction via a vacuum chuck (not shown). The reticle stage RST is finely drivable in a horizontal plane (XY plane), and is scanned by a reticle stage driving unit 49 in a predetermined stroke range in a scanning direction (here, the Y direction which is the horizontal direction of the paper of FIG. 1). It has become so. The position and the rotation amount of the reticle stage RST during the scanning are measured by an external laser interferometer 54R via a movable mirror 52R fixed on the reticle stage RST, and the measured value of the laser interferometer 54R is used as a main controller. 50.

Note that the material used for the reticle R needs to be properly used depending on the wavelength of the exposure light IL. That is,
When using exposure light having a wavelength of 193 nm, synthetic quartz can be used. However, when using exposure light having a wavelength of 157 nm, it is necessary to use fluorite, synthetic quartz doped with fluorine, quartz, or the like.

The projection optical system PL is, for example, a double-sided telecentric reduction system, and includes a plurality of lens elements 70a, 70b,... Having a common optical axis in the Z-axis direction. As the projection optical system PL, one having a projection magnification β of, for example, １ ／, 、, 、, or the like is used. Therefore, as described above, when the illumination area 42R on the reticle R is illuminated by the exposure light IL, the image formed by reducing the pattern formed on the reticle R by the projection optical system PL at the projection magnification β is applied to the surface. Is projected onto a slit-shaped exposure region 42W on a wafer W on which a resist (photosensitive agent) is applied and transferred.

In the present embodiment, among the above lens elements, a plurality of lens elements can be independently moved. For example, the uppermost lens element 70a closest to the reticle stage RST is held by a ring-shaped support member 72.
Telescopic drive elements, for example, piezo elements 74a, 74
b, 74c (the drive element 74c on the far side of the drawing is not shown) is supported at three points and is connected to the lens barrel 76. The drive elements 74a, 74b, and 74c allow the three peripheral points of the lens element 70a to be independently moved in the optical axis AX direction of the projection optical system PL. That is, the lens element 70a can be translated along the optical axis AX according to the displacement of the driving elements 74a, 74b, 74c, and can be arbitrarily inclined with respect to a plane perpendicular to the optical axis AX. . Then, these drive elements 74a, 74b, 74
The voltage applied to c is controlled by the imaging characteristic correction controller 78 based on a command from the main controller 50, whereby the displacement of the driving elements 74a, 74b, 74c is controlled. In FIG. 1, the optical axis AX of the projection optical system PL refers to the optical axis of the lens element 70b fixed to the lens barrel 76 and other lens elements (not shown).

In the present embodiment, the relationship between the vertical amount of the lens element 70a and the change amount of the magnification (or distortion) is obtained in advance by experiments, and this is stored in the memory inside the main controller 50. The vertical amount of the lens element 70a is calculated from the magnification (or distortion) corrected by the main controller 50 at the time of correction, and an instruction is given to the imaging characteristic correction controller 78 to drive the drive elements 74a, 7a.
By driving the 4b and 74c, magnification (or distortion) correction is performed. The relationship between the vertical amount of the lens element 70a and the amount of change in magnification or the like may use an optically calculated value. In this case, an experiment is performed to determine the relationship between the vertical amount of the lens element 70a and the amount of change in magnification. Process can be omitted.

As described above, the lens element 70a closest to the reticle R is movable, but this element 70a is one of the elements whose influence on magnification and distortion characteristics is large and easy to control as compared with other lens elements. Is selected, and any lens element that satisfies the same condition may be configured to be movable to adjust the lens interval instead of the lens element 70a.

By moving at least one lens element other than the lens element 70a, other optical characteristics such as curvature of field, astigmatism, coma, and spherical aberration can be adjusted. In addition, by providing a sealed chamber between specific lens elements near the center of the projection optical system PL in the optical axis direction, and adjusting the pressure of gas in the sealed chamber by a pressure adjusting mechanism such as a bellows pump, An imaging characteristic correction mechanism for adjusting the magnification of the projection optical system PL may be provided. Alternatively, for example, an aspherical lens may be used as a part of the lens elements constituting the projection optical system PL, and the lens may be rotated. You may.
In this case, so-called rhombic distortion can be corrected. Alternatively, a parallel plane plate may be provided in the projection optical system PL, and the imaging characteristic correction mechanism may be configured by a mechanism that tilts or rotates it.

When a laser beam having a wavelength of 193 nm is used as the exposure light IL, synthetic quartz, fluorite or the like can be used as each lens element (and the above-mentioned parallel plane plate) constituting the projection optical system PL. But the wavelength 15
When using a laser beam of 7 nm, the projection optical system P
Fluorite is used for all materials such as lenses used for L.

The XY stage 14 is two-dimensionally driven by a wafer stage driving section 56 in the Y direction, which is the scanning direction, and the X direction, which is orthogonal to the scanning direction (the direction perpendicular to the plane of FIG. 1). A wafer W is held on a Z tilt stage 58 mounted on the XY stage 14 via a wafer holder 61 (not shown) by vacuum suction or the like. The Z tilt stage 58 adjusts the position (focus position) of the wafer W in the Z direction by, for example, three actuators (piezo elements or voice coil motors), and also adjusts the position of the wafer W with respect to the XY plane (the image plane of the projection optical system PL). It has the function of adjusting the inclination angle of. Also,
The position of the XY stage 14 is controlled by an external laser interferometer 5 via a movable mirror 52W fixed on a Z tilt stage 58.
4 W, and the measured value of the laser interferometer 54 W is supplied to the main controller 50.

Here, the movable mirrors actually include an X movable mirror having a reflective surface perpendicular to the X axis and a Y movable mirror having a reflective surface perpendicular to the Y axis. Interferometers for X-axis position measurement, Y-axis position measurement, and rotation (including yawing amount, pitching amount, and rolling amount) are provided, respectively. , A moving mirror 52W, and a laser interferometer 54W.

Further, on the Z tilt stage 58, a light receiving surface having the same height as the exposure surface of the wafer W is provided near the wafer W, and the amount of the exposure light IL passing through the projection optical system PL is detected. Dose monitor 59 is provided. The irradiation amount monitor 59 has a rectangular housing in plan view extending in the X direction, which is slightly larger than the exposure area 42W. A slit-shaped opening having substantially the same shape as the exposure area 42W is formed in the center of the housing. This opening is actually formed by removing a part of the light shielding film formed on the upper surface of the light receiving glass made of synthetic quartz or the like forming the ceiling surface of the housing. Si underneath the opening via a lens
An optical sensor having a light receiving element such as a system PIN type photodiode is arranged.

The irradiation amount monitor 59 is used for measuring the intensity of the exposure light IL applied to the exposure area 42W. A light amount signal corresponding to the amount of light received by the light receiving element constituting the irradiation amount monitor 59 is supplied to the main controller 50.

The optical sensor does not necessarily need to be provided inside the Z tilt stage 58. An optical sensor is provided outside the Z tilt stage 58, and the illumination light beam relayed by the relay optical system is transmitted through an optical fiber or the like. Needless to say, the light sensor may be guided to the optical sensor.

On the Z-tilt stage 58, a reference mark plate FM used for performing reticle alignment and the like described later is provided. The surface of the reference mark plate FM has substantially the same height as the surface of the wafer W. Reference marks such as a reticle alignment reference mark and a baseline measurement reference mark are formed on the surface of the reference mark plate FM.

Although not shown in FIG. 1 from the viewpoint of avoiding complicating the drawing, this exposure apparatus 10 actually has a reticle alignment system for performing reticle alignment.

When performing alignment of reticle R, first, reticle stage RST and XY stage 14 are driven by reticle stage driving section 49 and wafer stage driving section 56 by main controller 50, and rectangular exposure area 42W A reticle alignment reference mark on the reference mark plate FM is set, and the relative position between the reticle R and the Z tilt stage 58 is set so that the reticle mark image on the reticle R substantially overlaps the reference mark. In this state, both marks are imaged by the main controller 50 using the reticle alignment system.
Then, the imaging signal is processed to calculate the amount of displacement in the X and Y directions of the projected image of the reticle mark with respect to the corresponding reference mark.

A detection signal (image signal) of the projected image of the reference mark obtained as a result of the alignment of the reticle.
It is also possible to obtain a focus offset and a leveling offset (the focal position of the projection optical system PL, the image plane inclination, and the like) based on the contrast information included in.

In the present embodiment, at the time of the reticle alignment, the main controller 50 also measures the baseline amount of the wafer-side off-axis alignment sensor (not shown) provided on the side surface of the projection optical system PL. Done. That is, a reference mark for baseline measurement is formed on the reference mark plate FM in a predetermined positional relationship with respect to the reference mark for reticle alignment, and the amount of displacement of the reticle mark is measured via a reticle alignment system. At this time, by measuring the amount of displacement of the baseline measurement reference mark with respect to the detection center of the alignment sensor through the alignment sensor on the wafer side, the baseline amount of the alignment sensor, that is, the reticle projection position and the alignment sensor Are measured.

Further, as shown in FIG. 1, the exposure apparatus 10 of the present embodiment has a light source whose ON / OFF is controlled by the main controller 50, and is directed toward the image forming plane of the projection optical system PL. An irradiation optical system 60a for irradiating an image forming light beam for forming images of a large number of pinholes or slits obliquely with respect to the optical axis AX, and a wafer W of the image forming light beam
An obliquely incident light type multi-point focal position detection system (focus sensor) including a light receiving optical system 60b for receiving a light beam reflected on the surface is provided. The main controller 50 controls the inclination of the reflected light flux of the parallel plate (not shown) in the light receiving optical system 60b with respect to the optical axis, thereby offsetting the focus detection system (60a, 60b) in accordance with the focus fluctuation of the projection optical system PL. To perform the calibration. As a result, the image plane of the projection optical system PL and the surface of the wafer W coincide with each other within the range (width) of the depth of focus in the above-described exposure area 42W. The detailed configuration of the multipoint focus position detection system (focus sensor) similar to that of the present embodiment is disclosed in, for example, Japanese Patent Application Laid-Open No. 6-283403.

At the time of scanning exposure or the like, the main controller 50 controls the Z tilt stage 58 so that the defocus becomes zero based on a defocus signal (defocus signal) from the light receiving optical system 60b, for example, an S-curve signal. By controlling the Z position via a drive system (not shown), auto focus (auto focus) and auto leveling are executed.

The reason why a parallel plate is provided in the light receiving optical system 60b to provide an offset to the focus detection systems (60a, 60b) is that, for example, the focus is adjusted by moving the lens element 70a up and down for magnification correction. Also, since the projection optical system PL absorbs the exposure light IL, the imaging characteristics change and the position of the imaging surface fluctuates. In such a case, an offset is given to the focus detection system, and the focus detection system This is because it is necessary to match the in-focus position with the position of the imaging plane of the projection optical system PL. For this reason, in the present embodiment, the relationship between the vertical amount of the lens element 70a and the focus change amount is also obtained by an experiment in advance and stored in the memory inside the main control device 50. The lens element 70
A calculated value may be used for the relationship between the vertical amount of a and the focus change amount. Also, the auto-leveling may not be performed in the scanning direction, but may be performed only in the non-scanning direction orthogonal to the scanning direction.

The main controller 50 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), an RA
M (random access memory) or the like, and includes a so-called microcomputer (or workstation). In addition to performing the various controls described above, the reticle R is used to perform the exposure operation properly. , Scanning of the wafer W, stepping of the wafer W, exposure timing, and the like. Further, in the present embodiment, the main controller 50 controls the exposure amount at the time of scanning exposure as described later, calculates the amount of change in the imaging characteristics of the projection optical system PL by calculation, and On the basis of the result, an image forming characteristic of the projection optical system PL is adjusted via the image forming characteristic correcting controller 78, and the whole apparatus is controlled overall.

More specifically, main controller 50 synchronizes, for example, during scanning exposure, when reticle R is scanned via reticle stage RST in the + Y direction (or -Y direction) at a speed V _R = V. Then, the wafer W is moved in the −Y direction (or + Y direction) with respect to the exposure area 42W via the XY stage 14.
The laser interferometer 54 is scanned at a speed V _W = β · V (β is a projection magnification from the reticle R to the wafer W).
The positions and speeds of the reticle stage RST and the XY stage 14 are controlled via the reticle stage driving unit 49 and the wafer stage driving unit 56 based on the measured values of R and 54W, respectively. Further, at the time of stepping, main controller 50 controls XY stage 14 via wafer stage driving unit 56 based on the measurement value of laser interferometer 54W.
Control the position of.

Next, an exposure sequence when a reticle pattern is exposed on a predetermined number (N) of wafers W in exposure apparatus 10 of the present embodiment will be described.
The following description focuses on the control operation.

First, main controller 50 loads reticle R to be exposed onto reticle stage RST using a reticle loader (not shown).

Next, reticle alignment is performed using a reticle alignment system, and baseline measurement is performed.

Next, main controller 50 instructs a wafer transfer system (not shown) to replace wafer W. As a result, the wafer is exchanged (mere wafer loading when there is no wafer on the stage) by the wafer transfer system and a wafer transfer mechanism (not shown) on the XY stage 14, and then so-called search alignment and fine alignment (such as EGA) Is performed in a series of alignment steps.
Since the wafer exchange and wafer alignment are performed in the same manner as in a known exposure apparatus, further detailed description is omitted here.

Next, based on the alignment result and the shot map data, the operation of moving the wafer W to the scanning start position for exposure of each shot area on the wafer W and the above-described scanning exposure operation are repeated. Then, the reticle pattern is transferred to a plurality of shot areas on the wafer W by a step-and-scan method. During this scanning exposure, the main controller 50 issues a command to the light amount controller 16C while monitoring the output of the integrator sensor 46 to give the target integrated exposure amount determined according to the exposure conditions and the resist sensitivity to the wafer W. give. Thus, in the light amount control device 16C, the coarse adjustment of the exposure amount is performed by the first function, and the second function and the third function are adjusted.
Controls the frequency and peak power of the laser beam (ultraviolet pulsed light) from the light source device 16 to perform fine adjustment of the exposure amount.

The main controller 50 controls the illumination system aperture stop plate 24 via the driving device 40, and further synchronizes with the stage system operation information to move the movable reticle blind 30B.
Control the opening and closing operations of

When exposure of the first wafer W is completed, main controller 50 instructs a wafer transfer system (not shown) to replace wafer W. As a result, the wafer is exchanged by the wafer transfer system and the wafer transfer mechanism (not shown) on the XY stage 14, and thereafter, search alignment and fine alignment are performed on the replaced wafer in the same manner as described above. In this case, the main controller 50 causes the integrator sensor 46 and the reflected light monitor 47 to change the irradiation variation of the imaging characteristics (including the focus variation) of the projection optical system PL from the start of the exposure on the first wafer W.
Is given to the imaging characteristic correction controller 78 and an offset is given to the light receiving optical system 60b. Further, main controller 50 also obtains the atmospheric pressure fluctuation of the imaging characteristic of projection optical system PL based on the measurement value of atmospheric pressure sensor 77, and issues a command value for correcting this irradiation fluctuation to the imaging characteristic. It is provided to the correction controller 78 and the light receiving optical system 6
0b is given an offset.

Then, similarly to the above, the reticle pattern is transferred to a plurality of shot areas on the wafer W by the step-and-scan method.

In this case, the above-described rough adjustment of the exposure amount (light amount) may be performed by performing test emission before the actual exposure and performing control with accuracy of 1% or less with respect to the exposure amount set value. Good.

The dynamic range of the coarse adjustment of the exposure amount in the present embodiment can be set within a range of 1 to 1/128, but the dynamic range normally required is typically about 1 to 1/7. Therefore, the number of channels (the number of optical fibers) for which the optical output should be turned on may be controlled between 128 and 18. As described above, in the present embodiment, the coarse adjustment of the exposure amount according to the difference in the resist sensitivity or the like for each wafer can be accurately performed by controlling the exposure amount by individually turning on / off the optical output of each channel.

The light amount control by the second and third functions by the above-described light amount control device 16C is characterized by a high control speed and a high control accuracy. It is possible to surely satisfy the required control requirements.

Therefore, in order to control the exposure amount, the light amount control device 16C only needs to perform at least one of the light amount control by the second and third functions.

Also, in the exposure apparatus 10 of this embodiment, the exposure amount is controlled by combining any one of the light amount control by the second and third functions of the light amount control device 16C and the scanning speed. , Of course.

The exposure condition of the wafer W is changed according to the reticle pattern to be transferred onto the wafer W. For example, the intensity distribution of the illumination light on the pupil plane of the illumination optical system (ie, the shape of the secondary light source) Or the size), or an optical filter that shields a circular area centered on the optical axis on almost the pupil plane of the projection optical system PL is inserted and removed. The illuminance on the wafer W changes due to the change in the exposure condition, but this also occurs due to the change in the reticle pattern. this is,
This is due to the difference in the occupied area of the light shielding portion (or the transmission portion) of the pattern. Therefore, when the illuminance changes due to a change in the exposure condition and / or the reticle pattern, it is desirable to control at least one of the above-described frequency and peak power so that an appropriate exposure amount is given to the wafer (resist). . At this time, in addition to at least one of the frequency and the peak power, the scanning speed of the reticle and the wafer may be adjusted.

As described above in detail, according to the optical modulation device 160C of the present embodiment, the light modulator 310 transmits the light from the optical modulator 310 during periods other than the respective light pulse emission periods within the pulse train modulation period, which is the extinction period. based on the monitoring result of the injection light being, correction signal generator 330 generates a bias signal V _B for correcting the pulse train signal V _P for the pulse train modulated. Then, the pulse train signal V _P supplies the applied voltage V _C that is corrected by a bias signal V _B to the optical modulator 310, in the period of the pulse train modulated, sufficient extinction ratio of periods other than the light pulse emitted period Value can be maintained.

The light modulation device 160 according to the present embodiment
According to C, the correction signal generator 330 operates during the pulse train modulation period.
Intensity of light emitted from the optical modulator 310 during a period other than
From the optical modulator 310 during the pulse train modulation.
Average intensity (a · I _OUT)
Of each light pulse of the light pulse train emitted from the light source unit 16A.
Loose power can be made uniform. In addition, this embodiment
According to the light modulator 160C according to the embodiment, the applied voltage V_CBut
Voltage signal, and the optical modulator 310 is an electro-optical modulator.
Therefore, light modulation can be performed with high accuracy.

Also, the light modulation device 160 according to the present embodiment
According to C, the correction signal generator 330 is connected to the optical modulator 310
Light emitted synchronously detects from, so generating a bias signal V _B on the basis of the detection result, it is possible to set a good extinction and emission light intensity precision.

According to the light source device of this embodiment, since the pulse train modulation is performed by the light modulator 160C, the pulse power (energy) is high, the extinction ratio between light pulses is improved, and the pulse power is increased. A uniform light pulse train can be generated.

Further, according to the light source device of this embodiment, since the laser light source 160A is a single light source, a pulse train of a single wavelength can be emitted.

Further, according to the light source device of the present embodiment, since the wavelength conversion device 163 including the non-linear optical crystal that receives the light emitted from the optical amplification unit 161 and performs harmonic conversion is further provided, the exposure device UV light of a short wavelength suitable for the above can be generated.

Further, according to the light source device of the present embodiment, since the light shutter 17 for blocking the emission light during the period other than the pulse train modulation period in the light modulator 160C is further provided, only the light pulse train can be emitted. .

Since the exposure apparatus according to the present embodiment includes the above-described light source device 16 as an exposure beam generating device,
Exposure amount control can be accurately performed by pulse number control or pulse power control. Therefore, a predetermined pattern can be transferred onto the wafer W with improved exposure accuracy.

In the above embodiment, the optical modulator 310
However, as shown in FIG. 13, an optical modulator 310 ′ configured similarly to the optical modulator 310 may be connected in series to the optical modulator 310. Here, the optical modulator 31
When serially connecting 0 'and the optical modulator 310, the optical modulator 310' may be arranged on the upstream side or on the downstream side. Further, the applied voltage supplied to the optical modulator 310 ′ may or may not be corrected for improving the extinction ratio as in the optical modulator 310.

In the above embodiment, the optical amplifying unit 161
Has been described in the case of having a light path of 128 channels, but the number of light paths may be arbitrary, and a product to which the light source device according to the present invention is applied, for example, a specification (illuminance on a wafer) required in an exposure apparatus, The number may be determined according to the optical performance, that is, the transmittance of the illumination optical system or the projection optical system, the conversion efficiency of the wavelength conversion unit, the output of each optical path, and the like. Even in such a case, the control of the light amount and the exposure amount by the frequency control and the peak power control of the pulse light output from the light modulation device described above can be suitably applied.

Further, in the above-described embodiment, the wavelength of the ultraviolet light is set to be substantially the same as the wavelength of the ArF excimer laser or the F ₂ laser. However, the set wavelength may be arbitrarily set. And the laser light source 160A
, The configuration of the wavelength conversion unit 163, the harmonic magnification, and the like may be determined. The set wavelength may be determined, for example, according to the design rule (line width, pitch, etc.) of the pattern to be transferred onto the wafer. (Phase shift type or not) may be considered.

In the above embodiment, the laser light source 16
In order to control the oscillation wavelength of 0A, the laser light is monitored by the beam monitor mechanism 164 immediately after the laser light source 160A. However, the present invention is not limited to this. For example, as shown by a dotted line in FIG. The light beam is branched in the section 163 (or behind the wavelength conversion section 163), and is split into a beam monitor mechanism 183 similar to the beam monitor mechanism 164.
Alternatively, the monitoring may be performed. Then, based on the monitoring result by the beam monitoring mechanism 183, it is detected whether or not the wavelength conversion is performed accurately, and based on the detection result, the main controller 50 performs feedback control of the laser controller 16B. You may. Of course, using the monitoring results of both beam monitoring mechanisms,
The oscillation wavelength control of A may be performed.

In the above embodiment, the fly-eye lens system 22 is used as an optical integrator (homogenizer). However, a rod integrator may be used instead. In an illumination optical system using a rod integrator, the rod integrator is arranged so that its exit surface is substantially conjugate with the pattern surface of the reticle R. The blind 30A and the movable reticle blind 30B may be arranged.

Although not particularly described in the above embodiment, in the case of an apparatus for performing exposure with an exposure wavelength of 193 nm or less as in this embodiment, the light beam passing portion passes through a chemical filter. It is necessary to take measures such as filling or flowing clean air, dry air, N ₂ gas, or an inert gas such as helium, argon, or krypton, or evacuating the light passing portion.

The exposure apparatus of the above embodiment is manufactured by assembling various subsystems including each component so as to maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. Before and after this assembly, adjustments to achieve optical accuracy for various optical systems, adjustments to achieve mechanical accuracy for various mechanical systems, and various electric systems to ensure these various accuracy Are adjusted to achieve electrical accuracy. The assembling process from various subsystems to the exposure apparatus is performed by
Mechanical connection, wiring connection of an electric circuit, piping connection of a pneumatic circuit, and the like are included. It goes without saying that there is an assembling process for each subsystem before the assembling process from these various subsystems to the exposure apparatus. When the process of assembling the various subsystems into the exposure apparatus is completed, comprehensive adjustment is performed, and various precisions of the entire exposure apparatus are secured. It is desirable that the manufacture of the exposure apparatus be performed in a clean room in which the temperature, cleanliness, and the like are controlled.

Further, in the above embodiment, the case where the light source device according to the present invention is applied to the step-and-scan type scanning exposure apparatus has been described. The light source device according to the present invention can also be applied to a laser repair device used for cutting a part (such as a fuse) of the formed circuit pattern. Further, the light source device according to the present invention can be applied to an inspection device using visible light or infrared light. In this case, it is not necessary to incorporate the above-mentioned wavelength converter into the light source device. That is, the present invention is effective not only for an ultraviolet laser device but also for a laser device that generates a fundamental wave in the visible or infrared region and has no wavelength conversion unit. Further, the present invention is not limited to the step-and-scan type scanning exposure apparatus, but can be suitably applied to a static exposure type, for example, an exposure apparatus (stepper or the like) of a step-and-repeat type. Further, the present invention can be applied to a step-and-stitch type exposure apparatus, a mirror projection aligner, and the like.

The projection optical system and the illumination optical system shown in the above embodiments are only examples, and it goes without saying that the present invention is not limited to these. For example, the projection optical system is not limited to the refractive optical system, but may be a reflective system including only a reflective optical element, or a catadioptric system having a reflective optical element and a refractive optical element (a catadioptric system). Vacuum ultraviolet light (VUV light) with a wavelength of about 200 nm or less
In an exposure apparatus using, a catadioptric system may be used as the projection optical system. As the catadioptric projection optical system, for example, a catadioptric system having a beam splitter and a concave mirror as a reflective optical element, or a catadioptric system disclosed in Japanese Patent Application Laid-Open Nos. A catadioptric system having a concave mirror or the like can be used as a reflective optical element without using a beam splitter as disclosed in Japanese Unexamined Patent Publication No. Hei 8-334695 and Japanese Unexamined Patent Publication No. Hei 10-3039.

In addition, US Pat. No. 5,488,229
And a plurality of refractive optical elements and two mirrors (a primary mirror which is a concave mirror and a reflective surface formed on the side opposite to the incident surface of the refractive element or the parallel flat plate) disclosed in Japanese Patent Application Laid-Open No. 10-104513. And a reflection mirror that re-images an intermediate image of the reticle pattern formed by the plurality of refractive optical elements on the wafer by the primary mirror and the secondary mirror. A refraction system may be used. In this catadioptric system, a primary mirror and a secondary mirror are arranged following a plurality of refractive optical elements, and illumination light is reflected through a part of the primary mirror in the order of a secondary mirror and a primary mirror. Part to reach the wafer.

Of course, not only an exposure apparatus used for manufacturing a semiconductor element, but also an exposure apparatus for transferring a device pattern onto a glass plate and a thin-film magnetic head used for manufacturing a display including a liquid crystal display element and the like. The present invention can also be applied to an exposure apparatus used to transfer a device pattern onto a ceramic wafer, an exposure apparatus used to manufacture an imaging device (such as a CCD), and the like.

[0204]

As described above in detail, according to the optical modulation device of the present invention, it is possible to reduce
A correction signal generator generates a correction signal for correcting a main modulation signal, which is a pulse train signal for pulse train modulation, based on a result of monitoring light emitted from the optical modulator during a period other than each light pulse emission period. Therefore, the extinction ratio in a period other than each light pulse emission period in the pulse train modulation period can be maintained at a sufficient value.

Further, according to the light source device of the present invention, since the light emitted from the light source is pulse train-modulated by the optical modulator of the present invention and amplified by the optical fiber amplifier, the pulse power (energy) is large and the light pulse An optical pulse train with an improved extinction ratio can be generated.

Further, according to the exposure apparatus of the present invention, since the light source device of the present invention having the light blocking mechanism is provided as a device for generating an exposure beam, the exposure amount can be accurately controlled by controlling the number of pulses and the pulse power. . Therefore, a predetermined pattern can be transferred to the substrate with improved exposure accuracy.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an internal configuration of the light source device of FIG. 1 together with a main controller.

FIG. 3 is a diagram illustrating a configuration of the light modulation device in FIG. 2;

FIG. 4 is a graph showing characteristics of the optical modulator of FIG.

FIGS. 5A and 5B are diagrams for explaining a principle for obtaining a bias voltage at the time of extinction based on synchronous detection. FIG.

FIG. 6 is a timing chart for explaining processing of a monitor signal during a pulse train modulation period.

FIGS. 7A and 7B are diagrams for explaining how to obtain a bias voltage value during a period other than the pulse train modulation period.

FIG. 8 is a timing chart for explaining a process of generating a bias voltage in a period other than the pulse train modulation period.

FIG. 9 is a diagram showing a waveform of light emitted from an optical modulator.

FIG. 10 is a diagram schematically illustrating a configuration of an optical amplification unit in FIG. 2;

FIG. 11 is a diagram schematically showing a fiber amplifier constituting the optical amplification unit of FIG. 2 and a peripheral part thereof together with a part of a wavelength conversion unit.

FIG. 12A shows a fiber bundle 173;
The figure which shows the example of a structure of the wavelength conversion part which converts the fundamental wave of wavelength 1.544 micrometers emitted from the output terminal of a wavelength into an 8th harmonic (harmonic wave) using a nonlinear optical crystal, and generates 193 nm ultraviolet light. FIG. 12B shows the fiber bundle 17.
The wavelength of the fundamental wave having a wavelength of 1.57 μm emitted from the output terminal of No. 3 is converted into a 10th harmonic using a nonlinear optical crystal, and 157 is obtained.
FIG. 3 is a diagram illustrating a configuration example of a wavelength conversion unit that generates ultraviolet light of nm.

FIG. 13 is a diagram illustrating a configuration of a light modulation device according to a modification.

[Explanation of symbols]

10 Exposure device, 16 Light source device, 160A DFB semiconductor laser (light source), 160C Light modulation device, 161
Optical amplifying unit, 163 wavelength converting unit, 168 _n optical fiber amplifier, 171 _n optical fiber amplifier, 310 optical modulator (first optical modulator), 310 ′ optical modulator (second optical modulator) , 312... Optical path (first optical waveguide), 313... Optical path (second optical waveguide), 315a, 315b.
0: pulse generator, 330: correction signal generator, W: wafer (substrate).

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/30 527 F term (Reference) 2H079 AA02 AA12 BA03 CA24 EA05 EB05 FA01 HA02 HA13 KA11 2H097 AB09 BB01 BB02 CA07 CA13 CA17 GB01 LA10 LA12 2K002 AB12 CA02 DA01 DA08 HA20 HA32 5F046 AA07 BA04 BA05 CA04 DA02 DA03

Claims (17)

[Claims] 1. An optical modulator for modulating a pulse train of an incident light and emitting the light, wherein the first light whose transmittance changes in a range from substantially 0 to a predetermined value of 1 or less according to a value of the first modulation signal. A modulator;
A first pulse generator for generating a first main modulation signal toward the optical modulator; and a monitor result of light emitted from the optical modulator during a period other than each light pulse emission period in the pulse train modulation period. And a correction signal generator for generating a first correction signal for correcting the first main modulation signal to make the light emitted from the optical modulator zero during a period other than the light pulse emission period. Modulation device. 2. The apparatus according to claim 1, wherein said correction signal generator further generates a second correction signal for correcting the intensity of light emitted from said first optical modulator to a predetermined intensity during a period other than said pulse train modulation period. The light modulation device according to claim 1. 3. The optical modulation device according to claim 2, wherein the predetermined intensity is an average intensity of light emitted from the optical modulator during the period of the pulse train modulation. 4. The light modulation device according to claim 1, wherein the first modulation signal is an electric signal, and the first light modulator is an electro-optic modulator. . 5. The first modulation signal is a voltage signal; the first optical modulator is a first optical demultiplexer that divides the incident light into a first light and a second light; A first optical waveguide for guiding the first light; a second optical waveguide for guiding the second light and having a refractive index that varies according to an applied voltage value; and at least one of the second optical waveguides. A first electrode for applying a voltage according to the first modulation signal to a portion; the first light through the first waveguide;
A first light combining the second light with the second light passing through the second waveguide;
The optical modulator according to claim 4, further comprising a multiplexer. 6. The correction signal generator includes: a synchronous detector for synchronously detecting light emitted from the first optical modulator; and the first optical modulation during a period other than the light pulse emission period by the synchronous detector. A first bias signal to be added to the first main modulation signal based on a detection result of light emitted from the optical modulator, in order to make light emitted from the first optical modulator zero during a period other than the light pulse emission period. The light modulation device according to claim 4, further comprising a first bias generator that generates the light. 7. A second bias generator for generating a second bias signal for correcting a light intensity of light emitted from the first optical modulator to a predetermined intensity during a period other than the pulse train modulation period. The light modulation device according to claim 6, further comprising a modulator. 8. A second optical modulator connected in series with the first optical modulator, the transmittance of which varies in a range from approximately 0 to a predetermined value of 1 or less according to a value of the second modulation signal; The optical modulation device according to claim 1, further comprising: a second pulse generator that generates a second main modulation signal toward the second optical modulator. 9. The optical modulation device according to claim 8, wherein the second modulation signal is an electric signal, and the second light modulator is an electro-optic modulator. 10. The second modulation signal is a voltage signal, the second optical modulator includes: a second optical demultiplexer that divides incident light into third light and fourth light; A third optical waveguide that guides the third light; a fourth optical waveguide that guides the fourth light and changes the refractive index according to the applied voltage value; and at least one of the fourth optical waveguide. A second electrode for applying a voltage based on the second modulation signal to a portion; and the third light via the third waveguide;
A second optical coupler for multiplexing the fourth light with the fourth light via the fourth waveguide;
The optical modulator according to claim 9, further comprising a multiplexer. 11. An optical modulator for modulating a pulse train of incident light and emitting the light, wherein the transmittance of the incident light is substantially zero according to the value of the first modulation signal.
A first optical modulator that changes in a range from to a predetermined value equal to or less than 1; a first pulse generator that generates a first main modulation signal toward the first optical modulator; Are connected in series, and the transmittance is approximately 0 to 1 depending on the value of the second modulation signal.
A second optical modulator that changes in a range up to the following predetermined value; and a second optical modulator that generates a second main modulation signal toward the second optical modulator.
An optical modulation device comprising a pulse generator. 12. The apparatus according to claim 11, wherein the first modulation signal and the second modulation signal are electric signals, and the first light modulator and the second light modulator are electro-optic modulators. 3. The light modulation device according to claim 1. 13. A light source; a light modulator for performing pulse train modulation on light emitted from the light source; and light for amplifying light emitted from the light modulator. A light source device comprising a fiber amplifier. 14. The light source device according to claim 13, wherein the light source is a single wavelength laser light source. 15. The light source device according to claim 13, further comprising a wavelength conversion device including a non-linear optical crystal that receives the light emitted from the optical fiber amplifier and performs harmonic conversion. 16. The optical modulator according to claim 13, further comprising a light blocking mechanism provided on the downstream side of said optical fiber amplifier, for blocking emitted light in a period other than a pulse train modulation period in said light modulation device. The light source device according to claim 1. 17. An exposure apparatus for transferring a predetermined pattern onto a substrate by irradiating the substrate with an exposure beam, comprising the light source device according to claim 16 as a device for generating the exposure beam. Exposure equipment.