Patent Publication Number: US-2023136440-A1

Title: Exposure Device

Description:
TECHNICAL FIELD 
     The present invention relates to an exposure device using a laser as a light source, and particularly to an exposure device using a reflective liquid-crystal modulating device. 
     BACKGROUND ART 
     There is known an exposure device including an illumination device including a scanning device with scanning illumination light, an optical element that is a hologram recording medium on which scanning light impinges, a spatial light modulator illuminated by light from the optical element, and an imaging optical system forming an image of light modulated by the spatial light modulator on a target (Patent Document 1). In the device of Patent Document 1, the use of, for example, LCOS as the spatial light modulator is proposed. 
     However, the exposure performed using the scanning device requires time required for scanning, and unless the scanning is dense, uniformity of illumination cannot be improved, and there is a limit to improvement of the throughput while ensuring exposure accuracy. 
     As another exposure device, there is known a device including an illumination light source, an intensity-uniformized optical system, a digital micromirror device that forms a pattern, and a projection lens that projects the pattern formed by the digital micromirror device (Patent Document 2). 
     However, in the digital micromirror device, a tilt angle of a micromirror is large in-plane variation, and an individual difference between the devices is large, so that it is not easy to ensure the uniformity of in-plane illuminance. Further, in the digital micromirror device, it is not easy to finely control gradation, and when the gradation is finely controlled, display time tends to be long because the gradation is controlled by time division, so that there is a limit to improvement of throughput of exposure. The digital micromirror device requires inclined incident illumination, and the optical system is not easy to assemble. 
     Citation List 
     Patent Document 
     
         
         Patent Document 1: JP 2012-114358 A 
         Patent Document 2: JP 2001-135562 A 
       
    
     DISCLOSURE OF THE INVENTION 
     The present invention has been made in view of the above-described background art, and an object of the invention is to provide an exposure device capable of improving the exposure accuracy while ensuring throughput. 
     In order to achieve the above-mentioned object, an exposure device according to the present invention includes: a reflective liquid-crystal modulating device; a light source device uniformly illuminating the reflective liquid-crystal modulating device with power-stabilized and pulsed laser light in an ultraviolet wavelength band; a projection optical system forming an image of reflected light modulated by the reflective liquid-crystal modulating device; and a stage supporting a target on which exposure is performed by a pattern imaged by the projection optical system. 
     In the exposure device described above, the reflective liquid-crystal modulating device is uniformly illuminated with the pulsed laser light, and the exposure is performed on the target on the stage by the pattern imaged by the projection optical system from the reflected light modulated by the reflective liquid-crystal modulating device, so that the exposure throughput can be maintained while the illuminance adjustment by the reflective liquid-crystal modulating device is performed with high accuracy. It is noted that, when the exposure is performed by changing the region while moving the stage, there is a certain limit to a moving speed from the viewpoint of ensuring highly accurate stage movement, and it is easy to perform rewriting the pattern of the reflective liquid-crystal modulating device for each picture or screen at a speed corresponding to the speed limit. 
     According to the specific aspect of the present invention, in the exposure device, while moving the target by the stage, exposures are performed at predetermined periodic timing, and the pattern in the reflective liquid-crystal modulating device is rewritten between the exposures. In this case, the exposure can be performed while continuously moving the stage, and the exposure with high accuracy can be performed quickly. 
     According to another aspect of the present invention, while moving the stage, exposures are sequentially performed on different partial regions of the target to expose the entire target. In this case, an exposure pattern can be transferred with spatial resolution higher than a pixel density of the reflective liquid-crystal modulating device. 
     According to yet another aspect of the present invention, the light source device includes a pulse laser and generates exposure light with a pulse width that can be considered that the stage is substantially stopped. In this case, the exposure with a short pulse can be performed by the pulse laser while stabilizing the movement of the stage, and the accuracy of the exposure pattern can be improved. 
     According to yet another aspect of the present invention, superposed exposure is performed with a predetermined shift amount of the pixel pitch or less. In this case, the resolution can be improved by setting a predetermined shift amount and combining a superposed pattern. 
     According to yet another aspect of the present invention, the exposure device further includes: two reflective liquid-crystal modulators; and a beam splitter splitting and distributing the laser light from the light source device into the two reflective liquid-crystal modulating devices according to a polarized state, wherein the beam splitter synthesizes the reflected light modulated by the two reflective liquid-crystal modulating devices. In this case, multiple exposures can be performed, and a processing speed of the exposure can be increased. 
     According to yet another aspect of the present invention, the beam splitter is a polarizing beam splitter, light having different polarized states is incident on the two reflective liquid-crystal modulating devices, and the reflected light having different polarized states modulated by the two reflective liquid-crystal modulating devices is synthesized. In this case, the laser light from the light source device can be efficiently used. 
     According to yet another aspect of the present invention, the two reflective liquid-crystal modulating devices have substantially the same pixel array pattern and are arranged so as to cause the predetermined shift in the image synthesized by the polarizing beam splitter. In this case, the resolution can be improved by setting the predetermined shift amount and combining the pattern formed on the two reflective liquid-crystal modulating devices. 
     According to yet another aspect of the present invention, the predetermined shift is the pixel pitch or less. In this case, the resolution can be improved by setting the predetermined shift amount and combining the pattern formed on the two reflective liquid-crystal modulating devices. 
     According to yet another aspect of the present invention, the light source device monitors the pulsed laser light source and energy of the laser light from the pulsed laser light source and blocks an output of the laser light when the energy reaches to a predetermined threshold value. When the exposure is repeated while moving the stage, the energy level can be prevented from fluctuating with each exposure, and the exposure accuracy of the repeated exposure pattern can be improved as a whole. 
     According to yet another aspect of the present invention, the reflective liquid-crystal modulating device adjusts a line width of the pattern to be exposed to the target by controlling gradation of the reflected light. Compared with a digital mirror device, the reflective liquid-crystal modulating device can easily allow the gradation to be finer, can widen the adjustment range of the line width of the pattern, and can perform the exposure with high accuracy. 
     According to yet another aspect of the present invention, the exposure device further includes a surface observation system monitoring an alignment state of the pattern with respect to the target on the stage, wherein the surface observation system superposes and enables to observe the pattern on the reflective liquid-crystal modulating device and the pattern provided on the target on the stage. 
     According to yet another aspect of the present invention, the exposure device includes an autofocus system monitoring an image-formed state of a target on the stage. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a block diagram describing an overall configuration of an exposure device according to an embodiment; 
         FIG.  2    is a conceptual cross-sectional view describing a structure of a reflective liquid-crystal modulating device; 
         FIG.  3    is an explanatory diagram of an optical path from which a surface observation system is extracted; 
         FIG.  4    is an explanatory diagram of an optical path from which an autofocus system is extracted; 
         FIG.  5    is a diagram describing a structure of a laser output stabilizing device incorporated in a light source device; 
         FIGS.  6 A and  6 B  are diagrams describing an operation of a laser output stabilizing device; 
         FIG.  7    is a diagram describing a basic operation of exposure; 
         FIGS.  8 A to  8 F  are diagrams describing mode types of exposure; and 
         FIG.  9    is a diagram describing a method of adjusting a line width. 
     
    
    
     MODE(S) FOR CARRYING OUT THE INVENTION 
     Hereinafter, an exposure device according to an embodiment of the present invention and operations thereof will be described with reference to the drawings. 
     With reference to  FIG.  1   , an exposure device  100  according to the embodiment includes a light source device  10 , an optical modulation unit  20 , a projection optical system  30 , a target stage  40 , a lens stage  50 , and a control device  90 . The exposure device  100  includes a surface observation system  60  and an autofocus system  70  as portions associated with an exposure operation. 
     The light source device  10  is an illumination light source for ultraviolet rays, which denotes a wavelength of 10 to 400 nm, but practically, a wavelength of 300 to 400 nm is targeted. The light source device  10  includes a pulse laser  11 , a laser output stabilizing device  12 , a λ/2 wave plate  13 , a homogenizer  14 , relay lenses  15   a  and  15   b , and a laser controller  19 . The pulse laser  11  is a Q-switched pulse YAG laser and outputs, for example, an ultraviolet laser pulse having a wavelength of 355 nm in response to a trigger signal from an outside. The laser output stabilizing device  12  described in detail later is a portion for controlling an energy value of a laser pulse output from the light source device  10 . The λ/2 wave plate  13  is arranged to adjust a polarization direction of the laser beam output from the pulse laser  11  via the laser output stabilizing device  12 . The homogenizer  14  two-dimensionally homogenizes the laser beam, and the relay lenses  15   a  and  15   b  are portions for guiding a homogenized laser light bundle L11 to the optical modulation unit  20  with an appropriate size. The homogenizer  14  can have a configuration in which fly-eye lenses are used in two stages, but a light tunnel or other members can be used. The laser controller  19  operates under the control of the control device  90  and a stage controller  49 , outputs the trigger signal to the pulse laser  11 , and controls output timing of the ultraviolet laser pulse. 
     The optical modulation unit  20  includes two reflective liquid-crystal modulating devices  21  and  22 , a polarizing beam splitter  23 , lenses  24  and  25 , and a modulation control device  29 . The two reflective liquid-crystal modulating devices  21  and  22  have the same structure. The first reflective liquid-crystal modulating device  21 , also called LCOS (Liquid Crystal On Silicon), includes pixels in a matrix array that changes a polarized state. The first reflective liquid-crystal modulating device  21  spatially modulates the polarized state of the laser light bundle of an S-polarized component reflected by the polarizing beam splitter  23 . The second reflective liquid-crystal modulating device  22 , also called LCOS, includes pixels in a matrix array that changes the polarized state. The second reflective liquid-crystal modulating device  22  spatially modulates the polarized state of the laser light bundle of a P-polarized component transmitted through the polarizing beam splitter  23 . Herein, the first reflective liquid-crystal modulating device  21  and the second reflective liquid-crystal modulating device  22  have substantially the same pixel array or arrangement pattern. Laser light bundles having different polarized states are incident on the first reflective liquid-crystal modulating device  21  and the second reflective liquid-crystal modulating device  22  due to optical branching by the polarizing beam splitter  23 . The lenses  24  and  25  have a role of converting a main light beam of the laser light bundle with which the reflective liquid-crystal modulating devices  21  and  22  are illuminated into a parallel light bundle. The lenses  24  and  25  function as a portion of the projection optical system  30  in the sense that pattern surfaces  21   p  and  22   p  of the reflective liquid-crystal modulating devices  21  and  22  are projected onto a surface of a target work WO. Pattern light L12, which is the P-polarized component modulated by the first reflective liquid-crystal modulating device  21 , is converted into information reflecting a luminance pattern by passing through the polarizing beam splitter  23  and is incident on an objective lens  31 . The pattern light L12, which is the S-polarized component modulated by the second reflective liquid-crystal modulating device  22 , is converted into information reflecting the luminance pattern by being reflected by the polarizing beam splitter  23  and incident on the objective lens  31 . The modulation control device  29  operates under the control of the control device  90  and controls a pattern or an amount of rotation of the polarization angle to be formed by the reflective liquid-crystal modulating devices  21  and  22  in units of a pixel. 
       FIG.  2    is a cross-sectional view illustrating an example of a structure of the first reflective liquid-crystal modulating device  21 . The first reflective liquid-crystal modulating device  21  has the structure in which a liquid crystal layer  21   c  is interposed between a light transmitting substrate  21   a  and a circuit functional layer  21   b . A transparent electrode  21   t  is formed on a surface of the light transmitting substrate  21   a . The circuit functional layer  21   b  includes a circuit layer  21   g , a light-shielding layer  21   h , and a reflective pixel electrode layer  21   i  on an Si substrate  21   e . An alignment film or layer  21   j  is formed on the surface of the transparent electrode  21   t  covering the light transmitting substrate  21   a , and an alignment film  21   k  and a dielectric multilayer film  21   u  are formed on the surface of the reflective pixel electrode layer  21   i  on the liquid crystal layer  21   c  side. The first reflective liquid-crystal modulating device  21  is assumed to be used in the ultraviolet wavelength band, the light transmitting substrate  21   a  is made of synthetic quartz, the liquid crystal layer  21   c  has less absorption in an ultraviolet band (particularly in the wavelength band longer than 300 nm), the alignment films  21   j  and  21   k  are made of SiO 2 , and the reflective pixel electrode layer  21   i  is formed of the dielectric multilayer film. The first reflective liquid-crystal modulating device  21  has a structure that can withstand long-term use in the ultraviolet band. Although not illustrated, the second reflective liquid-crystal modulating device  22  also has the same structure as the first reflective liquid-crystal modulating device  21  and can withstand long-term use in the ultraviolet band. The first reflective liquid-crystal modulating device  21  and the second reflective liquid-crystal modulating device  22  have the feature where a display time hardly changes even if gradation is increased as compared with a digital micromirror device. Specifically, about 1000 shades or gradations can be achieved with 10-bit information, and desired light intensity can be achieved simply by performing irradiation with the laser light bundle L11 having desired energy in a pulse shape. It is noted that, in the case of the digital micromirror device, it is necessary to express gradation by time modulation, and there is a problem that the time required for exposure is increased as the gradation is increased. 
     Returning to  FIG.  1   , in the projection optical system  30 , the objective lens  31  cooperates with the lenses  24  and  25  of the optical modulation unit  20  to project the pattern light modulated by the optical modulation unit  20  onto the surface of the work WO supported on the target stage  40 , specifically, on a resist film. The objective lens  31  can achieve high resolution in response to ultraviolet rays. With respect to the resist film, when a required energy amount of light is applied, a chemical reaction does not occur instantly, but photosensing gradually progresses. Projection magnification by the projection optical system  30  is not particularly limited, and for example, 1 times magnification projection is possible, and 1/16 times projection is also possible. The specific objective lens  31  is of a 1/16 times reduced projection type, and has NA of, for example, about 0.75. When 1/16 times projection is performed, the pixel size of the reflective liquid-crystal modulating devices  21  and  22  is 8 µm, and the pixel size on the surface of the work WO is 0.5 µm. 
     The target stage  40  can support the work WO and move in an XY direction and can be rotated around an X axis, a Y axis, and a Z axis. The operation of the target stage  40  is controlled by the stage controller  49 , and under the control of the control device  90 , the work WO can be accurately moved to a predetermined position, and the work WO can be moved along a predetermined path at a desired speed. The work WO is, for example, the mask for exposure, but may be the semiconductor wafer or the like. 
     The lens stage  50  can move the objective lens  31  up and down in the Z direction. The operation of the lens stage  50  is controlled by the stage controller  49 , and under the control of the control device  90 , the objective lens  31  can be moved in the Z direction to finely adjust the focus state of the pattern projected onto the work WO. 
     The surface observation system  60  includes a surface observation light source  61 , a polarizing plate  62 , a dichroic half mirror prism  63 , a lens  64 , a polarizing plate  65 , a λ/4 plate  66 , and a CCD camera  67 . The surface observation system  60  is fixed relative to the optical modulation unit  20 . 
       FIG.  3    illustrates the surface observation system  60  extracted. The surface observation light source  61  is configured with, for example, an LED or the like and emits illumination light L21 (for example, yellow light having a wavelength of 567 nm or other visible light) having a long wavelength and causing substantially no photosensitivity to a resist formed on the surface of the work WO on the target stage  40 . The polarizing plate  62  cuts the S polarization and made P polarization to be selectively incident into the dichroic half mirror prism  63 . The dichroic half mirror prism  63  selectively reflects the illumination light L21 and allows the illumination light L21 in the P-polarized state to be incident on the first reflective liquid-crystal modulating device  21  via the polarizing beam splitter  23  and the lens  24 . The reflected light from the first reflective liquid-crystal modulating device  21  includes a P component and an S component. The polarizing beam splitter  23  branches the polarized light with respect to the laser light bundle L11 in the ultraviolet band and does not branch the polarized light with respect to the long-wavelength illumination light L21, and the reflected light as modulated light from the first reflective liquid-crystal modulating device  21  passes through the polarizing beam splitter  23  at least partially. The reflected light from the first reflective liquid-crystal modulating device  21  further partially passes through the dichroic half mirror prism  63 , passes through the λ/4 plate  66 , is incident on the objective lens  31  in a state where right-handed circular polarization and left-handed circular polarization are mixed, and allows the work WO on the target stage  40  to be illuminated with. Image light L22 from the work WO passes through the λ/4 plate  66  in a state where P polarization and S polarization are mixed, is partially reflected by the dichroic half mirror prism  63 , passes through the lens  64  and the like, and is incident on the CCD camera  67  via the polarizing plate  65 . In the above description, also with respect to the illumination light L21, the pattern or image formed by the first reflective liquid-crystal modulating device  21  is projected onto the surface of the work WO by the lens  24  and the objective lens  31 , and the surface image of the work WO is formed on the image sensor of the CCD camera  67  by the objective lens  31  and the lens  64 . The polarizing plate  65  prevents the illumination light L21 in the P-polarized state from the surface observation light source  61  from being directly incident on the CCD camera  67 . By using the surface observation system  60 , the pattern formed by the first reflective liquid-crystal modulating device  21  and the base pattern formed on the substrate of the work WO can be superposed and observed, and by operating the stage controller  49  while analyzing the observation result by the control device  90 , the target stage  40  can be appropriately moved with respect to the optical modulation unit  20  and the projection optical system  30 , so that the pattern or exposing image formed on the reflective liquid-crystal modulating device  21  can be formed at the appropriate position on the work WO. 
     The surface observation system  60  can not only observe the pattern of the first reflective liquid-crystal modulating device  21  but also observe the pattern of the second reflective liquid-crystal modulating device  22 . 
     Returning to  FIG.  1   , the autofocus system  70  includes an AF light source  71 , a polarizing plate  72 , a stripe pattern mask  73 , a polarizing beam splitter  74 , half mirror prisms  75  and  76 , and a first image sensor  77   a , a second image sensor  77   b , and an AF control circuit  79 . The autofocus system  70  shares the lens  64  and the dichroic half mirror prism  63  which constitutes the surface observation system  60 . 
       FIG.  4    illustrates the autofocus system  70  extracted. The AF light source  71  is configured with, for example, an LED or the like and emits illumination light L31 (for example, yellow light having a wavelength of 567 nm or other visible light) having a long wavelength causing substantially no photosensitivity to a resist formed on the surface of the work WO. In the present embodiment, the wavelength of the illumination light L31 is allowed to be matched with the wavelength of the illumination light L21 of the surface observation system  60 . The polarizing plate  72  cuts S polarization and allows the P polarization to be selectively incident on the stripe pattern mask  73  and the polarizing beam splitter  74 . The stripe pattern mask  73  is for projecting a stripe pattern on the surface of the work WO at the time of focusing. The polarizing beam splitter  74  transmits the illumination light L31 passing through the stripe pattern mask  73  as it is, and the half mirror prism  75  reflects the illumination light L31 in the P-polarized state and allows the illumination light L31 to be incident on the λ/4 plate  66  through the lens  64  and the dichroic half mirror prism  63 . A circularly polarized illumination light L31 passing through the λ/4 plate  66  is incident on the objective lens  31 , and the work WO on the target stage  40  is illuminated with the circularly polarized illumination light L31. An image light L32 in the circular polarized state from the work WO passes through the λ/4 plate  66  and becomes S-polarized, is partially reflected by the dichroic half mirror prism  63  and passes through the lens  64  and the like, is bent along the optical path by the half mirror prism  75 , and is incident on the polarizing beam splitter  74 . The image light L32 reflected by the polarizing beam splitter  74  so as not to return to the AF light source  71  is branched by the half mirror prism  76  and incident on the first image sensor  77   a  and the second image sensor  77   b . In the above description, with respect to the illumination light L31, the stripe pattern of the stripe pattern mask  73  is projected onto the surface of the work WO by the lens  64  and the objective lens  31 , and the stripe pattern on the work WO is projected onto the image sensors  77   a  and  77   b  by the objective lens  31  and the lens  64 . The operations of the image sensors  77   a  and  77   b  are controlled by the AF control circuit  79 , the AF control circuit  79  can determine whether the objective lens  31  is in a focused state or a front-focus state or a rear-focus state based on the contrast of an image detected by the image sensors  77   a  and  77   b , and can output such an in-focus state or an out-focus state to the control device  90 . It is noted that the first image sensor  77   a  is arranged in the state of being shifted to the front side with respect to the focused state, and the second image sensor  77   b  is arranged in the state of being shifted to the rear side with respect to the focused state. Therefore, the focused state can be achieved by stopping the ascending/descending of the objective lens  31  at the position where the contrast of the pattern detected by the first image sensor  77   a  and the contrast of the pattern detected by the second image sensor  77   b  match with each other while the objective lens  31  is moved up and down in the Z direction by the lens stage  50 . 
     In order to avoid interference, the operation of the surface observation light source  61  of the surface observation system  60  is stopped when the autofocus system  70  operates, and the operation of the AF light source  71  of the autofocus system  70  is stopped when the surface observation system  60  operates. It is noted that, during the exposure described later, the surface observation function is stopped by turning off the light source  61  of the surface observation system  60 , and the autofocus function is operated in real time by turning on the light source  71  of the autofocus system  70 . 
       FIG.  5    is a diagram illustrating an example of the structure of the laser output stabilizing device  12  incorporated in the light source device  10  illustrated in  FIG.  1   . The laser output stabilizing device  12  includes a beam splitter  12   a , a first photodiode  12   b , an optical delay circuit  12   c , an optical switch  12   d , a beam splitter  12   e , and a second photodiode  12   f  as an optical system. The laser output stabilizing device  12  includes an integrator  12   h , a comparator  12   i , and a switch driver  12   j  as a circuit system. In the laser output stabilizing device  12 , the first photodiode  12   b  can detect the change in the output energy of the pulse laser  11  at an ultra-high speed. An optical delay circuit  12   c  includes mirrors  12   p  and  12   q  and a prism mirror  12   r  and can compensate for the processing delay in the circuit system. The optical delay circuit  12   c  can also move the prism mirror  12   r  in a Dj direction, the optical path length directed toward the optical switch  12   d  can be extended, and the optical path length can be extended or shortened. The optical switch  12   d  has a Pockels cell  12   s  and a polarizing beam splitter  12   t  and can block the laser light bundle L11 emitted by switching the polarization direction driven by the switch driver  12   j . The second photodiode  12   b  is a sensor for determining whether or not the energy of the laser light bundle L11 output from the laser output stabilizing device  12  has reached a target value. In the above description, the Pockels cell  12   s  operates even with ultraviolet rays having a wavelength of about 300 nm. Further, the rise time of the operation is about 0.5 ns or less, and a high-speed switch process can be performed. 
       FIG.  6 A  is a chart illustrating the operation of the laser output stabilizing device  12  and illustrates an input laser waveform W1 detected by the first photodiode  12   b  and an integrated waveform W2 corresponding to the output of the integrator  12   h . The every-time light emission of the input laser waveform W1 is not always stable, and the emission intensity tends to vary when the input laser waveform W1 is emitted the plurality of times. The comparator  12   i  determines whether or not an energy value of the integrated waveform W2 has reached a predetermined threshold value TH, and when the energy value of the integrated waveform W2 reaches the predetermined threshold value TH, the switch driver  12   j  switches the Pockels cell  12   s  from off to on to block the laser light bundle L11.  FIG.  6 B  illustrates the waveform of the laser light bundle L11 output from the laser output stabilizing device  12 , and an output laser waveform W3 of the laser light bundle L11 is almost returned to zero at the stage when the energy value of the integrated waveform W2 reaches a predetermined threshold value TH. As the result, the energy of the laser light bundle L11 output from the light source device  10  can be precisely maintained at the target value and stabilized. 
     The exposure operation by the exposure device  100  will be described with reference to  FIG.  7   . The exposure region AR obtained by combining the plurality of partial regions RE arranged in a matrix is set on the photomask which is the work WO. In this case, 6 × 4 partial region RE is set, but the setting of the partial region RE can be appropriately changed according to the size of the work WO and the exposure accuracy. In the illustrated example, the partial region RE has, for example, the pixels of the first reflective liquid-crystal modulating device  21  having a pixel size of 0.5 µm × 0.5 µm to have 1920 pixels in the horizontal direction and 1200 pixels in the vertical direction and has a size of 0.6 mm × 0.96 mm. The work WO is reciprocated at equal intervals as illustrated by the locus TR by using the target stage  40 . At this time, intermittent scan type exposure is performed. In the specific embodiment, the width of the partial region RE in the Y direction is 0.96 mm, and the interval of the locus TR is also 0.96 mm. Further, when the work WO is scanned and moved by using the target stage  40  and the shot exposure is performed in synchronization with the scanning movement, the light emission and the exposure are performed by a pulse pattern PP as illustrated on the left side of the drawing. An exposure time te which is the pulse width can be set to a nanosecond level, and an exposure interval ti is set to, for example, 50 ms. During the exposure interval ti, rewriting of the pattern of the first reflective liquid-crystal modulating device  21  and the pattern of the second reflective liquid-crystal modulating device  22  is performed. In the case of the embodiment, since the vertical width of the partial region RE is moved by 0.6 mm at the exposure interval ti = 50 ms, the moving speed of the target stage  40  is 12 mm/s. When such a moving speed of the target stage  40  is assumed, the exposure time te at the nanosecond level is extremely short and equivalent to the work WO being substantially stationary, and namely, the exposure light can be generated in a time width that can be considered that the target stage  40  is substantially stopped, and an image shift does not occur during the exposure on the work WO. Moreover, the first reflective liquid-crystal modulating device  21  can be rewritten or switched during the relative movement of the work WO, and low-speed switching of the first reflective liquid-crystal modulating device  21  can be compensated for by the pulse exposure of the light bundle. 
     The exposure mode will be described with reference to  FIGS.  8 A to  8 F .  FIGS.  8 A and  8 B  are diagrams illustrating operation in a “1x” mode. In this case, only one of the reflective liquid-crystal modulating devices  21  and  22  is operated, pixels PX are arranged in a matrix shape to form a pattern region PA, and a beam spot BS0 corresponding to the pixel PX is formed on the projection side. At the center of the beam spot BS0, the beam center BC is illustrated for ease of viewing. In the “1x” mode, the pixel PX of the reflective liquid-crystal modulating device  21  can be exposed at the resolution substantially equal to the resolution obtained by reduction projection by the objective lens  31 .  FIGS.  8 C and  8 D  are diagrams illustrating operation in a “2x” mode. In this case, the first reflective liquid-crystal modulating device  21  and the second reflective liquid-crystal modulating device  22  are operated, but a pattern region PA11 of the first reflective liquid-crystal modulating device  21  and a pattern region PA21 of the second reflective liquid-crystal modulating device  22  are arranged to be shifted by half pixel in the -Y direction. Further, the exposure by the first reflective liquid-crystal modulating device  21  and the second reflective liquid-crystal modulating device  22  is performed with being shifted by half pixel in the X direction to perform double exposure, so that the exposure is also performed by the pattern regions PA12 and PA22. As clearly viewed from the arrangement of the beam spot BS and the beam center BC formed by these pattern regions PA11, PA21, PA12, and PA22, it can be seen that the exposure is performed with a grid pattern MP reduced to ½ in the vertical and horizontal directions. By the exposure in the above-mentioned “2x” mode, the edges of the transfer pattern can be smoothed, and the accuracy can be improved.  FIGS.  8 E and  8 F  are diagrams illustrating operation in a “4x” mode. In this case, the pattern region PA11 of the first reflective liquid-crystal modulating device  21  and the pattern region PA21 of the second reflective liquid-crystal modulating device  22  are arranged to be shifted by ¼ pixel in the -Y direction and to be shifted by half pixel in the -X direction. Further, the exposure by the first reflective liquid-crystal modulating device  21  and the second reflective liquid-crystal modulating device  22  is performed with being shifted by ¼ pixel in the X direction and with being shifted by half pixel in the -Y direction to perform double exposure, so that the exposure is also performed by the pattern regions PA12 and PA22. As clearly viewed from the arrangement of the beam spot BS and the beam center BC formed by these pattern regions PA11, PA21, PA12, and PA22, it can be seen that the pseudo exposure is performed with the grid pattern MP reduced to ¼ in the vertical and horizontal directions. It is noted that the exposure modes illustrated in  FIGS.  8 A to  8 F  are merely examples, and various types of double or more exposures with changed arrangements are possible. 
       FIG.  9    illustrates a beam profile of the exposure light in units of a pixel of the pattern light L12 projected onto the work WO and is a diagram illustrating the exposure on the gray scale. In the figure, the horizontal axis indicates the position on the work WO, and the vertical axis indicates the light intensity projected onto the work WO. By using the light source device  10  described above, the laser light bundle L11 having a stabilized energy value can be generated, and there is a feature that pulse exposure can be performed on a pattern of 1000 shades of gradation as the feature of the reflective liquid-crystal modulating devices  21  and  22 . Therefore, it can be seen that the line width of the resist can be adjusted in a range of LW1 to LW3 by various beams BF1 to BF3 of which gradations are adjusted, with the photosensitive threshold value of the resist as RT. Such grayscale exposure can be utilized, for example, in various exposure modes illustrated in  FIGS.  8 A to  8 F . 
     As clearly viewed from the above description, according to the exposure device  100  according to the above-described embodiment, the reflective liquid-crystal modulating devices  21  and  22  are uniformly illuminated with the pulsed laser light bundle L11, and the exposure is performed on the work WO that is a target on the target stage  40  by a pattern imaged by the projection optical system  30  from the pattern light L12 which is the reflected light modulated by the reflective liquid-crystal modulating devices  21  and  22 , so that the exposure throughput can be maintained while the illuminance adjustment by the reflective liquid-crystal modulating devices  21  and  22  is performed with high accuracy. It is noted that, when the exposure is performed by changing the region while moving the work support portion of the target stage  40 , there is a certain limit to a moving speed from the viewpoint of moving the work support portion of the target stage  40  with high accuracy, and it is easy to perform rewriting the patterns of the reflective liquid-crystal modulating devices  21  and  22  of each picture or screen at a speed corresponding to the speed limit. 
     The invention is not limited to the above-described embodiment, but the invention can be implemented in various embodiments without departing from the spirit thereof. For example, in the optical modulation unit  20 , an exposure pattern can be synthesized by combining three or more reflective liquid-crystal modulating devices. On the contrary, in the optical modulation unit  20 , it is not necessary to use the two reflective liquid-crystal modulating devices  21  and  22 , and the exposure can be performed only by the single reflective liquid-crystal modulating device  21 . However, when the exposure is performed only by the reflective liquid-crystal modulating device  21 , it is preferable to improve the light utilization efficiency by converting all the pulse lasers  11  generated by the light source device  10  into S-polarized light. Even when the exposure is performed only by the single reflective liquid-crystal modulating device  21 , by repeating the exposure with the locus TR as illustrated in  FIG.  7   , the superposed exposure can be performed with a predetermined shift amount of the pixel pitch or less similarly to the case illustrated in  FIG.  8 B  or the like. 
     The structures exemplified as the surface observation system  60  and the autofocus system  70  are merely examples, and it is possible to perform alignment in which the target stage  40  and the projection optical system  30  are appropriately arranged with respect to the optical modulation unit  20  by various methods. 
     A plurality of the optical modulation units  20  and a plurality of the projection optical systems  30  can be combined side by side to form the device that exposes the large area.