exposure equipment

Abstract

The present invention provides an exposure device with which it is possible to enhance exposure accuracy, while guaranteeing throughput. An exposure device (100) is provided with: reflective liquid-crystal modulating devices (21, 22); a light source device (10) that uniformly illuminates the reflective liquid-crystal modulating devices (21, 22) with uniform pulsed laser light in the ultraviolet wavelength band; a projection optical system (30) that forms an image with reflected light modulated by the reflective liquid-crystal modulating devices (21, 22); and a stage (40) that supports an item to be exposed with a pattern of the image formed by the projection optical system (30).

Description

[Technical Field]

[0001] The present invention relates to an exposure apparatus that uses a laser as a light source, and more particularly to an exposure apparatus that uses a reflective liquid crystal modulator. [Background technology]

[0002] A known exposure apparatus includes an illumination device including a scanning device that scans illumination light, an optical element that is a holographic recording medium onto which the scanning light is incident, a spatial light modulator that is illuminated by the light from the optical element, and an imaging optical system that images the light modulated by the spatial light modulator onto an object (Patent Document 1). In the apparatus of Patent Document 1, the use of, for example, an LCOS is proposed as the spatial light modulator.

[0003] However, exposure using a scanning device requires time for scanning, and unless the scanning is dense, the uniformity of illumination cannot be improved, and there are limits to improving throughput while maintaining exposure accuracy.

[0004] Another known exposure apparatus includes an illumination light source, an intensity uniforming 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).

[0005] However, digital micromirror devices have large in-plane variations in the tilt angle of the micromirrors and large individual differences between devices, making it difficult to ensure uniform in-plane illuminance. Furthermore, digital micromirror devices do not easily allow for fine gradation control, and when fine gradation is achieved, the display time tends to become longer because the gradation is controlled on a time-division basis, limiting the improvement of exposure throughput. Digital micromirror devices require oblique incidence illumination, making it difficult to assemble the optical system. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-114358 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-135562 Summary of the Invention

[0007] The present invention has been made in view of the above-mentioned background art, and has as its object to provide an exposure apparatus that can improve exposure accuracy while ensuring throughput.

[0008] In order to achieve the above object, the exposure apparatus of the present invention comprises a reflective liquid crystal modulator, a light source device that uniformly illuminates the reflective liquid crystal modulator with pulsed laser light in a homogenized ultraviolet wavelength range, a projection optical system that forms an image of the reflected light modulated by the reflective liquid crystal modulator, and a stage that supports an object to be exposed using the pattern formed by the projection optical system.

[0009] In the above exposure apparatus, the reflective liquid crystal modulator is uniformly illuminated with pulsed laser light, and the reflected light modulated by the reflective liquid crystal modulator is used to expose the target on the stage using a pattern formed by a projection optical system, so that it is possible to maintain exposure throughput while maintaining high precision in adjusting the illuminance by the reflective liquid crystal modulator. Note that when exposure is performed by changing the area while moving the stage, there is a certain limit to the movement speed in order to ensure high precision in stage movement, and it is easy to rewrite the pattern on the reflective liquid crystal modulator for each screen at a speed corresponding to this speed limit.

[0010] According to a specific aspect of the present invention, in the exposure apparatus, exposure is performed at a predetermined periodic timing while the target is moved by the stage, and the pattern is rewritten on the reflective liquid crystal modulator between exposures. In this case, exposure can be performed while the stage is continuously moved, allowing for rapid, high-precision exposure.

[0011] According to another aspect of the present invention, the entire target is exposed by sequentially exposing different partial areas of the target while moving the stage, which allows the exposure pattern to be transferred with a spatial resolution higher than the pixel density of the reflective liquid crystal modulator.

[0012] According to yet another aspect of the present invention, the light source device includes a pulsed laser and generates exposure light with a pulse width that allows the stage to be regarded as substantially stationary. In this case, short-pulse exposure is possible with the pulsed laser while stabilizing the movement of the stage, thereby improving the accuracy of the exposure pattern.

[0013] According to yet another aspect of the present invention, overlapping exposure is performed with a predetermined shift amount equal to or less than the pixel pitch, and in this case, the resolution can be improved by combining the setting of the predetermined shift amount with the overlapping pattern.

[0014] According to yet another aspect of the present invention, there is provided two reflective liquid crystal modulators and a beam splitter that splits and distributes laser light from a light source to the two reflective liquid crystal modulators according to the polarization state, and the beam splitter combines the reflected light modulated by the two reflective liquid crystal modulators. In this case, multiple exposure can be performed, and the exposure processing speed can be increased.

[0015] According to yet another aspect of the present invention, the beam splitter is a polarizing beam splitter that causes light beams with different polarization states to be incident on two reflective liquid crystal modulators and combines the reflected light beams with different polarization states that have been modulated by the two reflective liquid crystal modulators, thereby enabling efficient use of the laser light from the light source device.

[0016] According to yet another aspect of the present invention, the two reflective liquid crystal modulators have substantially the same pixel arrangement pattern and are arranged so as to cause a predetermined shift in the image combined by the polarizing beam splitter. In this case, the resolution can be improved by combining the setting of the predetermined shift amount with the patterns formed on the two reflective liquid crystal modulators.

[0017] According to yet another aspect of the present invention, the predetermined shift is equal to or less than the pixel pitch, and in this case, the resolution can be improved by combining the setting of the predetermined shift amount with the patterns formed on the two reflective liquid crystal modulators.

[0018] According to yet another aspect of the present invention, the light source device monitors the energy of the pulsed laser light source and the laser light from the pulsed laser light source, and cuts off the output of the laser light when the energy reaches a predetermined threshold. When exposure is repeated while moving the stage, fluctuations in the energy level between exposures can be prevented, and exposure accuracy can be improved overall for the repeated exposure pattern.

[0019] According to yet another aspect of the present invention, a reflective liquid crystal modulator adjusts the line width of a pattern to be exposed on a target by controlling the gradation of reflected light. Compared to digital mirror devices, a reflective liquid crystal modulator can easily achieve finer gradations and has a wider adjustment range for the line width of the pattern, enabling high-definition exposure.

[0020] According to yet another aspect of the present invention, a surface observation system is provided for monitoring the alignment state of the pattern relative to the object on the stage, and the surface observation system makes it possible to observe the pattern on the reflective liquid crystal modulation device and the pattern provided on the object on the stage in a superimposed manner.

[0021] According to yet another aspect of the present invention, an autofocus system is provided that monitors the imaging state of an object on a stage. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a block diagram illustrating the overall configuration of an exposure apparatus according to an embodiment. [Figure 2] 1 is a conceptual cross-sectional view illustrating the structure of a reflective liquid crystal modulation device. [Figure 3] FIG. 1 is an explanatory diagram of an optical path with a surface observation system removed. [Figure 4]FIG. 2 is an explanatory diagram of an optical path with an autofocus system removed. [Figure 5] 1A and 1B are diagrams illustrating the structure of a laser output stabilization device incorporated in a light source device. [Figure 6] 6A and 6B are diagrams illustrating the operation of the laser output stabilization device. [Figure 7] FIG. 2 is a diagram illustrating a basic exposure operation. [Figure 8] 8A to 8F are diagrams for explaining types of exposure modes. [Figure 9] FIG. 10 is a diagram illustrating a method for adjusting line width. DETAILED DESCRIPTION OF THE INVENTION

[0023] An exposure apparatus according to one embodiment of the present invention and its operation will be described below with reference to the drawings.

[0024] 1, exposure apparatus 100 of the embodiment includes a light source device 10, a light modulation unit 20, a projection optical system 30, an object stage 40, a lens stage 50, and a control device 90. Exposure apparatus 100 also includes a surface observation system 60 and an autofocus system 70 as parts associated with the exposure operation.

[0025] Light source device 10 is an ultraviolet illumination light source. Here, ultraviolet light refers to a wavelength of 10 to 400 nm, but in practice, wavelengths of 300 to 400 nm are targeted. Light source device 10 includes a pulsed laser 11, a laser output stabilizer 12, a λ / 2 wave plate 13, a homogenizer 14, relay lenses 15a and 15b, and a laser controller 19. Pulsed laser 11 is a Q-switched pulsed YAG laser that outputs ultraviolet laser pulses, for example, with a wavelength of 355 nm, in response to an external trigger signal. Laser output stabilizer 12, which will be described in detail later, controls the energy value of the laser pulses output from light source device 10. λ / 2 wave plate 13 is arranged to adjust the polarization direction of the laser beam output from pulsed laser 11 via laser output stabilizer 12. The homogenizer 14 homogenizes the laser beam two-dimensionally, and the relay lenses 15a and 15b guide the homogenized laser light beam L11 to the light modulation unit 20 at an appropriate size. The homogenizer 14 can be configured using two fly-eye lenses, but a light tunnel or other components can also be used. The laser controller 19 operates under the control of the control device 90 and the stage controller 49, outputs a trigger signal to the pulse laser 11, and controls the output timing of the ultraviolet laser pulse.

[0026] The light modulation unit 20 includes two reflective liquid crystal modulators 21 and 22, a polarizing beam splitter 23, lenses 24 and 25, and a modulation control device 29. The two reflective liquid crystal modulators 21 and 22 have the same structure. The first reflective liquid crystal modulator 21, also known as LCOS (Liquid Crystal on Silicon), includes pixels arranged in a matrix that change the polarization state. The first reflective liquid crystal modulator 21 spatially modulates the polarization state of the S-polarized component of the laser beam reflected by the polarizing beam splitter 23. The second reflective liquid crystal modulator 22, also known as LCOS, includes pixels arranged in a matrix that change the polarization state. The second reflective liquid crystal modulator 22 spatially modulates the polarization state of the P-polarized component of the laser beam that has passed through the polarizing beam splitter 23. The first reflective liquid crystal modulator 21 and the second reflective liquid crystal modulator 22 have approximately the same pixel arrangement pattern. Laser beams of different polarization states are incident on the first reflective liquid crystal modulator 21 and the second reflective liquid crystal modulator 22 due to optical branching by the polarizing beam splitter 23. The lenses 24 and 25 serve to collimate the principal rays of the laser beams illuminating the reflective liquid crystal modulators 21 and 22. The lenses 24 and 25 function as part of the projection optical system 30 to project the pattern surfaces 21p and 22p of the reflective liquid crystal modulators 21 and 22 onto the surface of the target workpiece WO. The pattern light L12, which is a P-polarized component modulated by the first reflective liquid crystal modulator 21, passes through the polarizing beam splitter 23 and is converted into information reflecting the luminance pattern, and then enters the objective lens 31. The pattern light L12, which is an S-polarized component modulated by the second reflective liquid crystal modulator 22, is reflected by the polarizing beam splitter 23 and is converted into information reflecting the luminance pattern, and then enters the objective lens 31. The modulation control device 29 operates under the control of the control device 90, and controls the pattern to be formed by the reflective liquid crystal modulation devices 21 and 22 or the amount of rotation of the polarization angle on a pixel-by-pixel basis.

[0027] 2 is a cross-sectional view illustrating an example of the structure of the first reflective liquid crystal modulator 21. The first reflective liquid crystal modulator 21 has a structure in which a liquid crystal layer 21c is sandwiched between a light-transmitting substrate 21a and a circuit functional layer 21b. A transparent electrode 21t is formed on the surface of the light-transmitting substrate 21a. The circuit functional layer 21b includes a circuit layer 21g, a light-shielding layer 21h, and a reflective pixel electrode layer 21i on a Si substrate 21e. An alignment film 21j is formed on the surface of the transparent electrode 21t covering the light-transmitting substrate 21a, and an alignment film 21k and a dielectric multilayer film 21u are formed on the surface of the reflective pixel electrode layer 21i facing the liquid crystal layer 21c. The first reflective liquid crystal modulator 21 is designed for use in the ultraviolet wavelength range. The light-transmitting substrate 21a is made of synthetic quartz, the liquid crystal layer 21c has low absorption in the ultraviolet range (especially wavelengths longer than 300 nm), the alignment films 21j and 21k are made of SiO2, and the reflective pixel electrode layer 21i is formed of a dielectric multilayer film. The first reflective liquid crystal modulator 21 has a structure that can withstand long-term use in the ultraviolet range. Although not shown, the second reflective liquid crystal modulator 22 has a similar structure to the first reflective liquid crystal modulator 21 and is also capable of withstanding long-term use in the ultraviolet range. Compared to digital micromirror devices, the first reflective liquid crystal modulator 21 and the second reflective liquid crystal modulator 22 have the advantage that the display time remains almost constant even when the number of gradations is increased. Specifically, approximately 1000 gradations can be achieved with 10-bit information, and the desired light intensity can be achieved simply by irradiating a pulsed laser beam L11 with the desired energy. In the case of a digital micromirror device, gradation expression by time modulation is required, and the more gradations there are, the longer the time required for exposure becomes.

[0028] Returning to FIG. 1 , in the projection optical system 30, the objective lens 31 cooperates with the lenses 24 and 25 of the light modulation unit 20 to project the pattern light modulated by the light modulation unit 20 onto the surface of the workpiece WO supported on the object stage 40, specifically onto a resist film. The objective lens 31 is capable of achieving high resolution with ultraviolet light. When the resist film is exposed to light with the required energy, a chemical reaction does not occur instantaneously, but rather the film gradually becomes photosensitive. There is no particular limit to the projection magnification of the projection optical system 30; for example, projection at 1x or 1 / 16x is possible. Specifically, the objective lens 31 is a 1 / 16x reduction projection type with, for example, an NA of approximately 0.75. For 1 / 16x projection, if the pixels or pixel size of the reflective liquid crystal modulation devices 21 and 22 are 8 μm, the pixel size on the surface of the workpiece WO is 0.5 μm.

[0029] The object stage 40 supports the workpiece WO and can move it in the X and Y directions, and can rotate it about the X, Y, and Z axes. The operation of the object stage 40 is controlled by a stage controller 49, and under the control of the control device 90, the object stage 40 can move the workpiece WO precisely to a predetermined position and move the workpiece WO along a predetermined path at a desired speed. The workpiece WO is, for example, a mask for exposure, but it may also be a semiconductor wafer or the like.

[0030] The lens stage 50 can raise and lower the objective lens 31 up and down in the Z direction. The operation of the lens stage 50 is controlled by a stage controller 49, and under the control of the control device 90, the objective lens 31 can be slightly moved in the Z direction to adjust the focus state of the pattern projected onto the workpiece WO.

[0031] 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 relatively to the light modulation unit 20.

[0032] FIG. 3 shows the surface observation system 60. The surface observation light source 61 is composed of, for example, an LED, and emits long-wavelength illumination light L21 (e.g., red light with a wavelength of 567 nm or other visible light) that is substantially non-photosensitive to the resist formed on the surface of the workpiece WO on the object stage 40. The polarizing plate 62 cuts S-polarized light and selectively allows P-polarized light to enter the dichroic half-mirror prism 63. The dichroic half-mirror prism 63 selectively reflects the illumination light L21, and allows the P-polarized illumination light L21 to enter the first reflective liquid crystal modulator 21 via the polarizing beam splitter 23 and lens 24. The reflected light from the first reflective liquid crystal modulator 21 contains P and S components. The polarizing beam splitter 23 splits the ultraviolet laser light beam L11 into polarized light, but does not split the long-wavelength illumination light L21 into polarized light. The reflected light from the first reflective liquid crystal modulator 21 passes at least partially through the polarizing beam splitter 23 as modulated light. The reflected light from the first reflective liquid crystal modulator 21 further passes partially through the dichroic half-mirror prism 63 and through the λ / 4 plate 66 to enter the objective lens 31 in a state where right-handed circularly polarized light and left-handed circularly polarized light are mixed, and illuminates the workpiece WO on the object stage 40. The image light L22 from the workpiece WO passes through the λ / 4 plate 66 to become a state where P-polarized light and S-polarized light are mixed, is partially reflected by the dichroic half-mirror prism 63, passes through the lens 64, etc., passes through the polarizing plate 65, and enters the CCD camera 67. In the above, also with regard to the illumination light L21, the pattern or image formed by the first reflective liquid crystal modulator 21 is projected onto the surface of the workpiece WO by the lens 24 and the objective lens 31, and an image of the surface of the workpiece 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 directly entering the CCD camera 67.By utilizing the surface observation system 60, the pattern formed by the first reflective liquid crystal modulator 21 and the base pattern formed on the substrate of the workpiece WO can be superimposed and observed, and by operating the stage controller 49 while analyzing the observation results using the control device 90, the object stage 40 can be moved appropriately relative to the light modulation unit 20 and the projection optical system 30, and the pattern or exposure image formed on the first reflective liquid crystal modulator 21 can be formed at an appropriate position on the workpiece WO.

[0033] The surface observation system 60 is capable of observing not only the pattern of the first reflective liquid crystal modulator 21 but also the pattern of the second reflective liquid crystal modulator 22 .

[0034] 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, a first image sensor 77a, a second image sensor 77b, and an AF control circuit 79. The autofocus system 70 shares the lens 64 and dichroic half-mirror prism 63 that constitute the surface observation system 60.

[0035] FIG. 4 shows the autofocus system 70. The AF light source 71 is composed of, for example, an LED, and emits long-wavelength illumination light L31 (e.g., red light or other visible light with a wavelength of 567 nm) that is substantially non-photosensitive to the resist formed on the surface of the workpiece WO. In this embodiment, the wavelength of the illumination light L31 is matched to the wavelength of the illumination light L21 from the surface observation system 60. The polarizing plate 72 cuts S-polarized light and selectively allows P-polarized light to enter the stripe pattern mask 73 and the polarizing beam splitter 74. The stripe pattern mask 73 projects a stripe pattern onto the surface of the workpiece WO when focused. The polarizing beam splitter 74 transmits the illumination light L31 that passes through the stripe pattern mask 73 as is, while the half-mirror prism 75 reflects the P-polarized illumination light L31 and directs it to the λ / 4 plate 66 via the lens 64 and the dichroic half-mirror prism 63. The circularly polarized illumination light L31 that passes through the λ / 4 plate 66 enters the objective lens 31 and illuminates the workpiece WO on the object stage 40. The circularly polarized image light L32 from the workpiece WO passes through the λ / 4 plate 66 and becomes S-polarized light. The image light L32 is partially reflected by the dichroic half mirror prism 63, passes through the lens 64, etc., has its optical path bent by the half mirror prism 75, and enters the polarizing beam splitter 74. The image light L32 that is reflected by the polarizing beam splitter 74 so as not to return to the AF light source 71 is split by the half mirror prism 76 and enters the first image sensor 77a and the second image sensor 77b. Regarding the illumination light L31, the stripe pattern of the stripe pattern mask 73 is projected onto the surface of the workpiece WO by the lens 64 and the objective lens 31, and the stripe pattern on the workpiece WO is projected onto the image sensors 77a and 77b by the objective lens 31 and the lens 64. The operation of the image sensors 77a and 77b is controlled by an AF control circuit 79, which can determine whether the objective lens 31 is in focus, in front focus, or in back focus from the contrast of the images detected by the image sensors 77a and 77b, and can output such focus state or out-of-focus state to the control device 90.The first image sensor 77a is positioned in a state shifted forward relative to the in-focus state, and the second image sensor 77b is positioned in a state shifted backward relative to the in-focus state. Therefore, while moving the objective lens 31 up and down in the Z direction by the lens stage 50, the in-focus state can be achieved by stopping the elevation of the objective lens 31 at a position where the contrast of the pattern detected by the first image sensor 77a and the contrast of the pattern detected by the second image sensor 77b match.

[0036] 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 is operating, and the operation of the AF light source 71 of the autofocus system 70 is stopped when the surface observation system 60 is operating. During exposure, which will be described later, the light source 61 of the surface observation system 60 is turned off to stop the surface observation function, while the light source 71 of the autofocus system 70 is turned on to operate the autofocus function in real time.

[0037] FIG. 5 illustrates an example of the structure of the laser output stabilizer 12 incorporated in the light source device 10 shown in FIG. The laser output stabilizer 12 includes, as its optical system, a beam splitter 12a, a first photodiode 12b, an optical delay circuit 12c, an optical switch 12d, a beam splitter 12e, and a second photodiode 12f. The laser output stabilizer 12 includes, as its circuit system, an integrator 12h, a comparator 12i, and a switch driver 12j. In the laser output stabilizer 12, the first photodiode 12b can detect changes in the output energy of the pulsed laser 11 at ultrahigh speed. The optical delay circuit 12m includes mirrors 12p and 12q and a prism mirror 12r, and can compensate for processing delays in the circuit system. The optical delay circuit 12c can also move the prism mirror 12r in the Dj direction, thereby extending the optical path length toward the optical switch 12d and shortening the optical path length. The optical switch 12d has a Pockels cell 12s and a polarizing beam splitter 12t, and is driven by a switch driver 12j to switch the polarization direction, thereby blocking the emitted laser beam L11. The second photodiode 12b is a sensor for determining whether the energy of the laser beam L11 output from the laser output stabilizer 12 is at a target value. In the above, the Pockels cell 12s is capable of operating with ultraviolet light having a wavelength of approximately 300 nm. In addition, the rise time of operation is approximately 0.5 ns or less, enabling high-speed switching processing.

[0038] FIG. 6A is a chart illustrating the operation of the laser output stabilizer 12, showing the input laser waveform W1 detected by the first photodiode 12b and the integrated waveform W2 corresponding to the output of the integrator 12h. The input laser waveform W1 is not necessarily stable with each emission, and the emission intensity tends to vary when emitted multiple times. The comparator 12i determines whether the energy value of the integrated waveform W2 reaches a predetermined threshold TH. If the integrated waveform W2 reaches the predetermined threshold TH, the switch driver 12j switches the Pockels cell 12s from off to on, blocking the laser beam L11. FIG. 6B shows the waveform of the laser beam L11 output from the laser output stabilizer 12. The output laser waveform W3 of the laser beam L11 returns to almost zero when the energy value of the integrated waveform W2 reaches the predetermined threshold TH. As a result, the energy of the laser beam L11 output from the light source device 10 can be precisely stabilized at a target value.

[0039] The exposure operation by the exposure apparatus 100 will be described with reference to FIG. 7. An exposure area AR is defined on the photomask, which is the workpiece WO, by combining multiple partial areas RE arranged in a matrix. In this example, 6 × 4 partial areas RE are defined, but the definition of the partial areas RE can be changed as appropriate depending on the size of the workpiece WO and the exposure accuracy. In the illustrated example, the partial area RE has a size of 0.6 mm × 0.96 mm, assuming that the pixels of the first reflective liquid crystal modulator 21 are 0.5 μm × 0.5 μm, there are 1920 pixels horizontally, and 1200 pixels vertically. Using the target stage 40, the workpiece WO is moved back and forth at equal intervals as shown by the trajectory TR. During this process, intermittent scanning exposure is performed. In a specific example, the width of the partial area RE in the Y direction is 0.96 mm, and the spacing of the trajectory TR is also 0.96 mm. Furthermore, when performing shot exposure in synchronization with the scanning movement of the workpiece WO using the object stage 40, light emission and exposure are performed using a pulse pattern PP as shown on the left side of the drawing. The exposure time te, which is the pulse width, can be set to the nanosecond level, and the exposure interval ti is, for example, 50 ms. During the exposure interval ti, the patterns of the first reflective liquid crystal modulator 21 and the second reflective liquid crystal modulator 22 are rewritten. In this embodiment, the exposure interval ti = 50 ms, and the partial area RE is moved by a vertical width of 0.6 mm, so the movement speed of the object stage 40 is 12 mm / s. Given this movement speed of the object stage 40, the nanosecond-level exposure time te is extremely short and is equivalent to the workpiece WO being substantially stationary. In other words, the exposure light can be generated for a time duration that can be considered as if the object stage 40 is substantially stationary, and no image shift occurs during exposure on the workpiece WO. Moreover, the first reflective liquid crystal modulator 21 can be rewritten or switched while the workpiece WO is moving relatively, and the slow switching speed of the first reflective liquid crystal modulator 21 can be compensated for by pulse exposure of the light beam.

[0040] The exposure modes will be described with reference to FIGS. 8A to 8F. FIGS. 8A and 8B are diagrams illustrating operation in the "1x" mode. In this case, only one of the reflective liquid crystal modulators 21 and 22 is operated. The pixels PX are arranged in a matrix to form a pattern area PA. A beam spot BS0 corresponding to the pixel PX is formed on the projection side. A beam center BC is indicated at the center of the beam spot BS0 for ease of viewing. In the "1x" mode, exposure is possible at a resolution substantially equal to the resolution obtained by reducing and projecting the pixels PX of the reflective liquid crystal modulator 21 using the objective lens 31. FIGS. 8C and 8D are diagrams illustrating operation in the "2x" mode. In this case, the first reflective liquid crystal modulator 21 and the second reflective liquid crystal modulator 22 are operated, but the pattern area PA11 of the first reflective liquid crystal modulator 21 and the pattern area PA21 of the second reflective liquid crystal modulator 22 are shifted by half a pixel in the -Y direction. Furthermore, exposure by the first reflective liquid crystal modulator 21 and the second reflective liquid crystal modulator 22 is offset by half a pixel in the X direction, resulting in double exposure. The arrangement of the beam spots BS and beam centers BC formed by these pattern regions PA11, PA21, PA12, and PA22 clearly shows that exposure is performed using a grid pattern MP that is reduced by half both vertically and horizontally. Exposure in the "2x" mode described above smooths the edges of the transferred pattern and increases its resolution. Figures 8E and 8F illustrate operation in the "4x" mode. In this case, the pattern region PA11 of the first reflective liquid crystal modulator 21 and the pattern region PA21 of the second reflective liquid crystal modulator 22 are offset by a quarter pixel in the -Y direction and a half pixel in the -X direction. Furthermore, exposure is also performed by pattern areas PA12 and PA22 by shifting the exposure by the first reflective liquid crystal modulator 21 and the second reflective liquid crystal modulator 22 by a quarter pixel in the X direction and a half pixel in the -Y direction, thereby performing double exposure. As is clear from the arrangement of the beam spots BS and beam centers BC formed by these pattern areas PA11, PA21, PA12, and PA22, it can be seen that exposure is performed in a manner similar to a grid pattern MP that is reduced vertically and horizontally to a quarter.It should be noted that the exposure modes shown in FIGS. 8A to 8F are merely examples, and it goes without saying that various types of double or more exposures are possible by changing the arrangement.

[0041] FIG. 9 illustrates the beam profile of the exposure light in pixel units of the pattern light L12 projected onto the workpiece WO, illustrating grayscale exposure. In the figure, the horizontal axis represents the position on the workpiece WO, and the vertical axis represents the light intensity projected onto the workpiece WO. The light source device 10 described above can generate a laser beam L11 with a stabilized energy value, and the reflective liquid crystal modulators 21 and 22 are characterized by their ability to pulse-expose patterns with 1,000 gradations. Therefore, it can be seen that, with the resist's photosensitivity threshold set to RT, the resist line width can be adjusted within the range of LW1 to LW3 using various beams BF1 to BF3 with adjusted gradations. Such grayscale exposure can be utilized in various exposure modes, such as those shown in FIGS. 8A to 8F.

[0042] As is clear from the above explanation, according to the exposure apparatus 100 of the above embodiment, the reflective liquid crystal modulators 21, 22 are uniformly illuminated with a pulsed laser beam L11, and the pattern light L12, which is reflected light modulated by the reflective liquid crystal modulators 21, 22, is used to expose the workpiece WO, which is the target on the object stage 40, with a pattern formed by the projection optical system 30, so that it is possible to maintain exposure throughput while highly accurately adjusting the illuminance by the reflective liquid crystal modulators 21, 22. Note that when exposure is performed by moving the work support part of the object stage 40 to change the area, there is a certain limit to the movement speed from the perspective of moving the work support part of the object stage 40 with high precision, and it is easy to rewrite the pattern of the reflective liquid crystal modulators 21, 22 for each screen at a speed corresponding to this speed limit.

[0043] The present invention is not limited to the above-described embodiments and can be embodied in various forms without departing from the spirit and scope of the present invention. For example, the light modulation unit 20 can combine three or more reflective liquid crystal modulators to synthesize an exposure pattern. Conversely, the light modulation unit 20 does not need to use two reflective liquid crystal modulators 21 and 22, and can be configured to perform exposure using only a single reflective liquid crystal modulator 21. However, when performing exposure using only the reflective liquid crystal modulator 21, it is desirable to increase light utilization efficiency by converting all pulsed laser light 11 generated by the light source device 10 into S-polarized light. Even when performing exposure using only a single reflective liquid crystal modulator 21, by repeating exposure along the locus TR shown in FIG. 7, it is possible to perform superimposed exposure or superimposed exposure with a predetermined shift amount equal to or less than the pixel pitch, as in the case shown in FIG. 8B, etc.

[0044] The structures illustrated as the surface observation system 60 and the autofocus system 70 are merely examples, and various methods can be used to align the object stage 40 and the projection optical system 30 to the light modulation unit 20 appropriately.

[0045] A plurality of light modulation units 20 and projection optical systems 30 can be arranged and combined to form an apparatus for exposing a large area.

Claims

1. two reflective liquid crystal modulators; a light source device that uniformly illuminates the two reflective liquid crystal modulation devices with a uniform pulsed laser beam in the ultraviolet wavelength range; a polarizing beam splitter that splits and distributes the laser light from the light source device to the two reflective liquid crystal modulators according to a polarization state, and combines the reflected light modulated by the two reflective liquid crystal modulators; a projection optical system that forms an image using the reflected light modulated by the two reflective liquid crystal modulators; a stage for supporting an object to be exposed by a pattern imaged by the projection optical system; While moving the object by the stage, partial areas arranged in a grid pattern on the object are sequentially exposed at predetermined periodic timing, thereby exposing the entire object; Rewriting patterns for the two reflective liquid crystal modulation devices between exposures; the light source device includes a pulse laser, and generates exposure light for each partial region with a pulse width that allows the stage to be regarded as substantially stationary; The two reflective liquid crystal modulation devices each have a reflective pixel electrode formed of a dielectric multilayer film, the two reflective liquid crystal modulators have substantially the same pixel arrangement pattern and are arranged to cause a predetermined shift in the image synthesized by the polarizing beam splitter; Exposure equipment.

2. 2. The exposure apparatus according to claim 1, wherein overlapping exposure is performed with a predetermined shift amount equal to or less than the pixel pitch.

3. 3. The exposure apparatus according to claim 1, wherein the polarizing beam splitter causes light of different polarization states to be incident on the two reflective liquid crystal modulators, and combines reflected light of different polarization states modulated by the two reflective liquid crystal modulators.

4. 4. The exposure apparatus according to claim 1, wherein the light source device is a pulsed laser light source, and monitors the energy of the laser light from the pulsed laser light source, and cuts off the output of the laser light when the energy reaches a predetermined threshold.

5. 5. The exposure apparatus according to claim 4, wherein said reflective liquid crystal modulation device adjusts the line width of a pattern to be exposed onto an object by controlling the gradation of reflected light.

6. a surface observation system for monitoring an alignment state of the pattern relative to the object on the stage; 6. The exposure apparatus according to claim 1, wherein the surface observation system makes it possible to observe a pattern on the reflective liquid crystal modulation device and a pattern provided on the target on the stage in a superimposed manner.

7. 7. The exposure apparatus according to claim 1, further comprising an autofocus system that monitors an imaging state for the object on the stage.

Images