JP2011197554A - Optical modulation device and exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical modulation device which has a high-power resistance and high resistance to optical damage with respect to short wavelength light and achieves high-speed modulation, and to provide an exposure device using the optical modulation device.SOLUTION: An electro-optical crystal substrate 15 having an outer shape of a quadrangular prism is formed in such a manner that the periphery of an electro-optical crystal layer 11 is surrounded by a crystal part 14 (electro-optical crystal layers 12, 13) with both end faces 11a, 11b exposed. Electrodes 16a, 16b are formed on the upper surface and lower surface of the electro-optical crystal substrate 15, respectively. The electrodes 16a, 16b are electrically connected with a potential applying part 17. When a positive potential and a negative potential are supplied from the potential applying part 17 to the electrodes 16a, 16b, the refractive indexes of the electro-optical crystal layer 11 and the crystal part 14 are increased and reduced, respectively. Incident light Lin is confined in the electro-optical crystal layer 11 and propagated. When the opposite potential is applied, the incident light Lin is spread so as to be sucked into the crystal part 14.

Description

  The present invention relates to a light modulation device using an electro-optic crystal and an exposure apparatus equipped with the light modulation device.

As a light modulation device using an electro-optic crystal, for example, a Mach-Zehnder type light modulation device is widely known. This light modulation device is a device in which two optical waveguides branching to an electro-optic crystal whose refractive index changes due to an electric field such as lithium niobate (LiNbO ₃ ) are formed, and voltage is applied to these optical waveguides. Is used for optical modulation. In other words, a phase difference is provided by changing the phase of light in the optical waveguide by applying voltage, and interference is used when combining the light propagating through each optical waveguide. It will be in the ON state and will be in the OFF state in the case of reverse phase.

“Applied Physics Handbook” edited by the Society of Applied Physics, Maruzen Co., Ltd., March 30, 1990, p. 109

  In the optical modulation device configured as described above, the optical waveguide is bent relatively gently while avoiding a sharp bend of the optical waveguide in order to suppress optical loss that occurs when the optical waveguide is branched or combined. For this reason, it is necessary to design the light modulation device long in the light propagation direction in which light travels through the optical waveguide, and it is not uncommon for the length of the device in the light propagation direction to exceed 5 cm. In addition, in order to prevent the light propagating through the optical waveguides from affecting each other, the optical waveguides must be sufficiently separated in the width direction orthogonal to the light propagation direction. This is a major obstacle to increasing density. In general, the width of the optical waveguide is about several microns and is formed by a method such as proton exchange or titanium diffusion. As a result, the refractive index of the optical member constituting the optical waveguide is relatively high, and the force for confining light in the optical waveguide is increased. Therefore, in order to avoid a multimode, that is, to make the optical waveguide into a single mode waveguide, the width of the optical waveguide in the width direction is designed to be as narrow as several microns. Fortunately, even in a bent portion where light branching or photosynthesis is performed, light loss can be reduced and light can be guided well. However, on the other hand, due to such a technical background, the width of the optical waveguide has to be narrowed to increase the power density in the optical waveguide, and there are problems such as optical damage in the power resistance limit and short wavelength light. Has occurred.

  The present invention has been made in view of the above problems, and provides a light modulation device having high power resistance performance, high optical damage performance with short wavelength light, and capable of high-speed modulation, and an exposure apparatus using the light modulation device The purpose is to provide.

  In order to achieve the above object, the light modulation device according to the present invention includes a first electro-optic crystal layer that guides light incident from one end face in the first direction and emits the light from the other end face. An electro-optic crystal substrate configured to be sandwiched from a second direction orthogonal to the first direction by a second electro-optic crystal layer and a third electro-optic crystal layer having a crystal axis orientation different from that of the optical crystal layer; The first electrode provided on the surface of the electro-optic crystal layer, the second electrode provided on the surface of the third electro-optic crystal layer, and the potential applied to the first electrode and the second electrode are controlled to control the incident light. And a potential applying unit that changes the refractive index of the first electro-optic crystal layer, the second electro-optic crystal layer, and the third electro-optic crystal layer to change the intensity of light emitted from the other end face.

  In order to achieve the above object, an exposure apparatus according to the present invention modulates a light modulation device configured as described above, a light source unit that makes light incident on one end face of the first electro-optic crystal layer, and a light modulation device. And an optical system that guides the modulated light emitted from the other end face of the first electro-optic crystal layer to the exposed surface.

  In the invention thus configured (light modulation device and exposure apparatus), the first electro-optic crystal layer is formed by using the second electro-optic crystal layer and the third electro-optic crystal having a crystal axis orientation different from that of the first electro-optic crystal layer. An electro-optic crystal substrate is formed by sandwiching the layers. In addition, the first electrode is provided on the surface of the second electro-optic crystal layer, and the second electrode is provided on the surface of the third electro-optic crystal layer, and a potential is applied to these electrodes from the potential applying unit. It is done. Then, by controlling the potential difference between the first electrode and the second electrode, the direction and magnitude of the electric field generated between the first electrode and the second electrode can be changed. On the other hand, in the electro-optic crystal substrate, the refractive indexes of the first electro-optic crystal layer, the second electro-optic crystal layer, and the third electro-optic crystal layer with respect to the light incident on the first electro-optic crystal layer correspond to the electric field, respectively. Value. Thus, by controlling the potential application to the first electrode and the second electrode, it is possible to control the refractive index distribution state in the electro-optic crystal substrate. The intensity of light guided by one electro-optic crystal layer and emitted from the other end face changes. That is, light modulation can be performed by controlling the potentials of the first electrode and the second electrode.

  Here, the second electro-optic crystal layer and the third electro-optic crystal layer are integrally formed to form a crystal part, and the crystal part surrounds the first electro-optic crystal layer in a cross section with respect to the first direction. Also good. In this case, the first electro-optic crystal layer is the core by potential control, and the light incident on the first electro-optic crystal layer is caused by the action of the electro-optic crystal substrate, like an optical waveguide whose crystal portion corresponds to the clad. It is possible to propagate in the first direction while confining within the first electro-optic crystal layer.

  Further, the second electro-optic crystal layer and the third electro-optic crystal layer are formed apart from each other in the second direction, that is, the electro-optic crystal substrate is arranged in the second direction (second electro-optic crystal layer-first electro-optic crystal). It may be configured to have a three-layer structure of (layer-third electro-optic crystal layer).

  Further, the crystal axis orientations of the first electro-optic crystal layer and the crystal axis orientations of the second electro-optic crystal layer and the third electro-optic crystal layer may be different from each other. It is desirable to do. In addition, it is desirable that the crystal axis orientation of the first electro-optic crystal layer and the crystal axis orientations of the second and third electro-optic crystal layers are parallel to the second direction. . Further, the first electro-optic crystal layer, the second electro-optic crystal layer, and the third electro-optic crystal layer may be composed of the same type of crystal. In this case, when the same potential is applied to the first electrode and the second electrode, This is equivalent to forming the electro-optic crystal substrate with the same crystal as a whole.

  The length of the first electro-optic crystal layer in the first direction is preferably 1 mm or more and 50 mm or less, and the thickness of the first electro-optic crystal layer in the second direction is preferably 5 μm or more and 100 μm or less. .

  Furthermore, the number of the first electrodes and the second electrodes is not limited to “1”, and a plurality of the first electrodes and the second electrodes may be provided, thereby obtaining a multi-channel light modulation device. That is, n (n ≧ 2) first electrodes are provided on the first surface of the second electro-optic crystal layer so as to be separated from each other in the third direction orthogonal to the first direction and the second direction, and the second electrode is provided N electrodes spaced apart from each other in the third direction and provided on the second surface of the third electro-optic crystal layer, and composed of a first electrode and a second electrode facing each other across the first electro-optic crystal layer N pairs may be provided. Then, by independently controlling the potential applied to the n pairs of electrodes, light modulation can be performed independently on each electrode pair. In this case, the first electrode and the second electrode are extended in parallel with the first direction, so that light modulation at each electrode pair can be performed stably.

  According to the present invention, the light applied to the first electro-optic crystal layer is controlled by controlling the potential applied to the first electrode and the second electrode, thereby controlling the refractive index distribution in the electro-optic crystal substrate. Since modulation is performed, high-speed optical modulation is possible. In addition, when the refractive index in the electro-optic crystal substrate is changed by applying a potential difference, since the change in the refractive index is slight, the cross-sectional area of the first electro-optic crystal layer with respect to the propagation direction (first direction) of incident light. Can be set relatively wide, and even if high-power light or short-wavelength light is incident on the first electro-optic crystal layer, light modulation can be performed without causing defects such as light damage. That is, high power resistance performance and optical damage performance with short wavelength light can be enhanced.

It is a figure which shows 1st Embodiment of the light modulation device concerning this invention. It is a figure which shows typically the structure and operation | movement of a light modulation device of FIG. It is a graph which shows the result of the simulation by BPM method in an ON state. It is a graph which shows the result of the simulation by the BPM method in an intermediate state. It is a graph which shows the result of the simulation by BPM method in an OFF state. It is a figure which shows 2nd Embodiment of the light modulation device concerning this invention. It is a figure which shows 3rd Embodiment of the light modulation device concerning this invention. It is a figure which shows 4th Embodiment of the light modulation device concerning this invention. It is a figure which shows 5th Embodiment of the light modulation device concerning this invention. It is a figure which shows one Embodiment of the exposure apparatus equipped with the light modulation device concerning this invention. It is a figure which shows other embodiment of the exposure apparatus equipped with the light modulation device concerning this invention. It is a perspective view which shows the main-body part of the exposure apparatus shown in FIG. It is a block diagram which shows the electric constitution of the exposure apparatus of FIG. It is a figure which simplifies and shows the internal structure of an optical head. It is a perspective view of a slit board.

<First Embodiment of Optical Modulation Device>
FIG. 1 is a diagram showing a first embodiment of a light modulation device according to the present invention. FIG. 1A is a perspective view of the light modulation device, and FIGS. 1B to 1D are views of the light modulation device. It is a figure which shows a light modulation operation | movement typically. FIG. 2 is a diagram schematically showing the configuration and operation of the light modulation device of FIG. This light modulation device 1A includes a uniaxial electro-optic crystal layer 11 having a quadrangular prism shape extending in the Z direction. Both end surfaces 11a and 11b of the electro-optic crystal layer 11 have a rectangular shape. When light Lin enters the electro-optic crystal layer 11 through the one end surface 11a, the electro-optic crystal layer 11 is guided in the direction Z. The light is emitted from the other end face 11b. As the electro-optic crystal layer 11, uniaxial electro-optic crystals such as LN (LiNbO ₃ ) and LT (LiTaO ₃ ) can be used, for example.

  In addition, electro-optic crystal layers 12 and 13 made of the same material as the electro-optic crystal layer 11 are disposed so as to sandwich the electro-optic crystal layer 11 from the vertical direction Y perpendicular to the light propagation direction Z. These electro-optic crystal layers 12 and 13 are integrated to form a crystal portion 14. That is, the electro-optic crystal substrate 15 having a quadrangular prism appearance is formed by surrounding the electro-optic crystal layer 11 with the crystal portion 14 (electro-optic crystal layers 12 and 13) with both end faces 11a and 11b exposed. Has been.

  Further, in the present embodiment, as will be described later, since r33 having the largest electrooptic coefficient is used, the crystal axis orientation of the electrooptic crystal layer 11 (also referred to as the crystal C axis orientation) is the end face 11a of FIG. It is facing upward as shown by the arrow in the middle. On the other hand, the crystal part 14 has an orientation different from the crystal axis orientation of the electro-optic crystal layer 11. In particular, in this embodiment, the crystal axis orientation of the crystal part 14 is shifted by 180 ° from the crystal axis orientation of the electro-optic crystal layer 11. In other words, the direction is opposite to the electro-optic crystal layer 11. As described above, the arrow in the crystal portion 14 indicates the direction of polarization (this also applies to the drawings described later).

  The upper surface of the electro-optic crystal substrate 15 thus configured (the upper surface of the electro-optic crystal layer 12) is finished in a horizontal plane parallel to the XZ plane, and the first electrode 16a is formed on the entire upper surface. Further, the lower surface of the electro-optic crystal substrate 15 (the lower surface of the electro-optic crystal layer 12) is also finished in a horizontal plane parallel to the XZ plane. The second electrode 16b is formed on the entire lower surface of the electro-optic crystal substrate 15, and the electro-optic crystal substrate 15 is sandwiched between the two electrodes 16a and 16b in the vertical direction Y. The electrodes 16a and 16b are electrically connected to the potential applying unit 17, and the potential applying unit 17 can arbitrarily control the potential applied to the electrodes 16a and 16b. Then, by applying a potential difference between the electrodes 16a and 16b, an electric field is generated in a direction parallel to the crystal axis orientation of the electro-optic crystal layer 11 and the crystal portion 14, that is, the vertical direction Y. Therefore, by controlling the potential difference between the first electrode 16a and the second electrode 16b, the direction and magnitude of the electric field can be changed. As will be described next, in the electro-optic crystal substrate 15, The distribution state of the refractive index can be controlled, and the intensity of the light Lout emitted from the other end face 11b of the first electro-optic crystal layer 11 changes according to the distribution state of the refractive index.

  When the same potential is applied to the electrodes 16a and 16b and the potential difference is set to zero as shown in FIGS. 1C and 2B, the entire electro-optic crystal substrate 15 has a refractive index with respect to the incident light Lin. It is equivalent to “n” uniform crystals. Therefore, when an extraordinary single-mode light (light having a Gaussian distribution) Lin polarized in the direction of the crystal axis is incident on the electro-optic crystal layer 11 through the one end face 11a of the electro-optic crystal layer 11, the light Lin is one. The light propagates in a single mode in the light propagation direction Z through the inside of the electro-optic crystal substrate 15 while spreading in a divergent manner in the same manner as in propagation in such a crystal. Therefore, the intensity of the light Lout emitted from the other end face 11b of the electro-optic crystal layer 11 gradually decreases as the length of the electro-optic crystal substrate 15 in the light propagation direction Z increases. A state in which the potential difference is set to zero and light Lout having a relatively low light intensity is emitted is referred to as an “intermediate state”. In the following description, “refractive index” means a refractive index with respect to incident light Lin unless otherwise specified.

  Further, as shown in FIGS. 1B and 2A, the potential of the electro-optic crystal layer 11 on the crystal axis orientation side, that is, the upper electrode 16a is higher than the potential of the lower electrode 16b. When a voltage is applied, an electric field directed from top to bottom is generated in the electro-optic crystal substrate 15 and the refractive index of the electro-optic crystal layer 11 is increased by Δne to become (n + Δne), while the crystal portion 14 (electro-optics). The refractive index of the crystal layers 12, 13) decreases by Δne and becomes (n−Δne). For this reason, the electro-optic crystal substrate 15 acts like an optical waveguide in which the electro-optic crystal layer 11 is a core and the crystal portion 14 surrounding the electro-optic crystal layer 11 in a cross section orthogonal to the light propagation direction Z corresponds to a clad. The light Lin is confined in the electro-optic crystal layer 11 and propagates in the light propagation direction Z in a single mode. Therefore, the intensity of the light Lout emitted from the other end face 11b of the electro-optic crystal layer 11 is higher than that in the intermediate state (the state shown in FIG. 1B or FIG. 2B). The state in which the voltage L is applied and the light Lout having a relatively high light intensity is emitted from the other end surface 11b of the electro-optic crystal layer 11 is referred to as an “ON state”.

  In addition, a voltage opposite to the ON state is applied, that is, as shown in FIGS. 1D and 2C, the potential of the electrode 16a on the crystal axis orientation side of the electro-optic crystal layer 11, that is, the upper electrode 16a is When a voltage is applied so as to be lower than the potential of the lower electrode 16b, an electric field directed from the bottom to the top is generated in the electro-optic crystal substrate 15, and the refractive index of the electro-optic crystal layer 11 is decreased by Δne, On the other hand, the refractive index of the crystal part 14 (electro-optic crystal layers 12 and 13) is increased by Δne and becomes (n + Δne). Thus, since the refractive index of the crystal part 14 is higher than that of the electro-optic crystal layer 11 in the central part, the light Lin incident on the electro-optic crystal layer 11 spreads so as to be actively sucked into the crystal part 14. . Therefore, as the length of the electro-optic crystal substrate 15 in the light propagation direction Z increases, the intensity of the light Lout emitted from the other end face 11b of the electro-optic crystal layer 11 decreases extremely, and the light intensity is higher than that in the intermediate state. It is even lower and close to zero. A state in which the intensity of the light Lout emitted from the other end surface 11b of the electro-optic crystal layer 11 by applying a voltage in this way is nearly zero is referred to as an “OFF state”.

As described above, according to the light modulation device 1 </ b> A according to the first embodiment, the light emitted from the other end surface 11 b of the electro-optic crystal layer 11 by controlling the potential applied from the potential applying unit 17 to the electrodes 16 a and 16 b. The intensity of Lout can be favorably modulated, and high-speed light modulation is possible. Here, in order to verify the modulation performance of the optical modulation device 1 </ b> A configured as described above, the following conditions are provided: Electro-optic crystal layers 11 to 13: LN (LiNbO ₃ )
End faces 11a and 11b of the electro-optic crystal layer 11: 30 μm square Thickness of the crystal part 14: 15 μm
・ Length in Z direction: 20mm
-Crystal axis (C axis) orientation of the electro-optic crystal layer 11: upward (on the first electrode 16a side)
-Crystal axis (C-axis) orientation of crystal part 14: downward (second electrode 16b side)
-Wavelength λ of incident light Lin: 633 nanometers (nm)
-Potential application in the ON state: 10 V from top to bottom
-Potential application in the intermediate state: potential difference 0V
・ Electric potential application in OFF state: 10V from bottom to top
A two-dimensional BPM (Beam Propagation Method) method is used to simulate an extraordinary Gaussian beam polarized in the direction of the crystal axis of 1 / e diameter and 30 μm of the light peak. did.

  FIG. 3 is a graph showing the result of simulation by the BPM method in the ON state. In this ON state, as shown in FIGS. 1B and 2A, the refractive index of the electro-optic crystal layer 11 increases by Δne and becomes (n + Δne), while the crystal portion 14 (electro-optic crystal layer) 12 and 13) is decreased by Δne to (n−Δne), and the electro-optic crystal substrate 15 is like an optical waveguide in which the electro-optic crystal layer 11 is a core and the crystal portion 14 is a clad. Works. As can be seen from the simulation results, the light Lout can be emitted from the electro-optic crystal layer 11 while suppressing light loss.

  FIG. 4 is a graph showing the result of simulation by the BPM method in the intermediate state. In this intermediate state, as shown in FIGS. 1C and 2B, the entire electro-optic crystal substrate 15 is the same as a crystal having a uniform refractive index. As can be seen from the simulation results, the incident light propagates in the single-mode in the light propagation direction Z in the light propagation direction Z while spreading in a divergent manner in the same manner as propagating in a uniform crystal. The intensity of the light Lout emitted from the other end face 11b of the crystal layer 11 does not decrease to zero, but is significantly reduced compared to the ON state.

  FIG. 5 is a graph showing the result of simulation by the BPM method in the OFF state. In this OFF state, as shown in FIGS. 1D and 2C, the refractive index of the crystal portion 14 is higher than that of the electro-optic crystal layer 11 in the central portion. As can be seen from the simulation results, the incident light is actively guided to the crystal portion 14 and the intensity of the light Lout emitted from the other end face 11b of the electro-optic crystal layer 11 is further reduced from the intermediate state, and is zero. The value is close to.

As described above, according to the light modulation device 1A according to the present embodiment, three-stage light modulation can be performed with excellent modulation performance. Of course, the number of stages of modulation is not limited to “3”, and the potential applied to the first electrode 16a and the second electrode 16b is switched to two stages for ON / OFF control, or conversely, the number of potential switching stages is set. It is also possible to perform gradation modulation by increasing the number. That is, the absolute value Δne of the change amount of the refractive index changes according to the electric field generated between the electrodes 16a and 16b as shown in the following equation. Further, the sign is determined by the crystal axis orientation and the electric field orientation, and in the same case, it decreases by (−) minus, and in the opposite case, it increases by (+) plus. The symbol Γ in the equation is an electric field reduction coefficient.

By controlling the generation of the electric field in this way, the light L can be modulated by changing the change amount Δne of the refractive index. However, as shown in the following equation, the electric field is the gap g between the electrodes 16a and 16b in the direction Y (see FIG. 1 (c)) and the potential difference v between the electrodes 16a and 16b.

Therefore, the following equation is obtained by substituting Equation 2 into Equation 1. As is apparent from the following equation, it is understood that the refractive index change Δne can be controlled by controlling the potential difference v.

For example, the electro-optic crystal layers 11 to 13 are all composed of LN (LiNbO ₃ ). Further, when the one end face 11a and the other end face 11b of the electro-optic crystal layer 11 are set to 30 μm square and the thickness of the crystal part 14 is set to 15 μm, the gap g between the electrodes 16a and 16b in the direction Y becomes 60 μm. Then, an extraordinary ray of light Lin having a wavelength λ of 633 nm and polarized in the direction of the crystal axis is incident on one end face 11a of the electro-optic crystal layer 11, and a potential is applied to the first electrode 16a and the second electrode 16b at a voltage v = 10V. Is calculated based on Equation 3, the refractive index change Δne is about 2.73 × 10 ⁻⁵ . Here, the calculation is performed on the assumption that the electric field reduction coefficient Γ is 1.

Further, in the optical modulation device 1A having the configuration shown in FIG. 1, the refractive index difference changes in the opposite direction between the central portion and the peripheral portion, so that the refractive index difference of the entire device is 2 × Δne≈5.46 × 10 ^{−. 5} , which is much smaller than a normal optical waveguide such as an optical fiber. Accordingly, when used in the ON state as shown in FIGS. 1B and 2A, the electro-optic crystal layer 11 is a core and the crystal portion 14 is an optical waveguide corresponding to a cladding. Although the crystal substrate 15 acts, the force for confining the light Lin in the electro-optic crystal layer (core portion) 11 is very weak. Therefore, if fundamental mode light, that is, light having a Gaussian distribution is allowed to pass through the electro-optic crystal layer 11, for example, “Introduction to optical waveguide analysis” written by Tetsuro Tsuji, published by Morikita Publishing, October 5, 2007, p. Based on the theory of mode propagation described in 43 to 46, etc., a waveguide of several tens of μm is required, and a sufficiently large incident cross section and output cross section are required as compared with the optical waveguide of an optical fiber or an integrated optical circuit. . In this way, widening the end surfaces 11a and 11b of the electro-optic crystal layer 11 is directly connected to reducing the light energy density in the electro-optic crystal layer 11, and reduces high energy light propagation or optical damage. It is suitable for. That is, according to the present embodiment, the cross-sectional area of the electro-optic crystal layer 11 with respect to the propagation direction (first direction) Z of the incident light Lin can be set relatively wide, and high-power light and short-wavelength light can be electrically Even if the light is incident on the optical crystal layer 11, light modulation can be performed without causing problems such as light damage.

  In the above embodiment, the electrodes 16a and 16b are formed on the entire upper surface (the upper surface of the electro-optic crystal layer 12) and the entire lower surface (the lower surface of the electro-optic crystal layer 12) of the electro-optic crystal substrate 15, respectively. For this reason, the interaction range between the electric field generated between the electrodes 16a and 16b and the incident light Lin is widened, and light modulation can be performed at a low voltage.

  Further, since the electro-optic crystal layer 11 and the crystal portion 14 (electro-optic crystal layers 12 and 13) are made of the same material, the light Lin is transmitted when the potential difference between the electrodes 16a and 16b is zero. Therefore, the light can be favorably modulated.

  In the first embodiment, the light modulation device 1A in which the length of the first electro-optic crystal layer 11 in the light propagation direction Z corresponding to the “first direction” of the present invention is set to 20 mm has excellent light modulation performance. As described above, the length of the first electro-optic crystal layer 11 in the light propagation direction Z is preferably set to 1 mm or more and 50 mm or less. This is because of the following reason. Since this length corresponds to the interaction distance between the light and the electric field (E), the drive voltage can be lowered and the high-speed modulation can be achieved by increasing the length. In the OFF state, the light Lout emitted from the first electro-optic crystal layer 11 is reduced by light escaping from the first electro-optic crystal layer 11 to the crystal portion 14 as described above. The extinction ratio can be increased. For this reason, in order to perform light modulation at a low voltage, it is necessary to set the length of the first electro-optic crystal layer 11 in the light propagation direction Z to 20 mm and at least 1 mm. Further, although the voltage drop and the extinction ratio are improved as the first electro-optic crystal layer 11 is lengthened in the Z direction, the manufacturing limit of an ingot (wafer) from which the electro-optic crystal is cut out is desired to be smaller than the conventional light modulation device. From the standpoints of such a demand and a decrease in light intensity due to light attenuation, it is desirable to make it 50 mm or less.

  Furthermore, in the first embodiment, the light modulation device 1A in which the thickness of the first electro-optic crystal layer 11 in the vertical direction Y corresponding to the “second direction” of the present invention is set to 30 μm exhibits excellent light modulation performance. As described above, the thickness of the first electro-optic crystal layer 11 in the vertical direction Y is preferably set to 5 μm or more and 100 μm or less. This is because of the following reason. Since the electric field is generated in the electro-optic crystal substrate 15 as described above, when the thickness of the first electro-optic crystal layer 11 in the vertical direction Y corresponding to the “second direction” of the present invention increases. Therefore, it becomes necessary to increase the potential difference between the electrodes 16a and 16b, and when it exceeds 100 μm, only a modulation speed equivalent to or lower than that of the conventional device can be obtained. Therefore, in order to ensure high-speed modulation, it is desirable to suppress the thickness of the first electro-optic crystal layer 11 to 100 μm or less. In the light modulation device 1A, even when the potential difference between the electrodes 16a and 16b is controlled, the first electro-optic crystal layer 11 and the crystal portion 14 (the second electro-optic crystal layer 12 and the third electro-optic crystal layer 113). The refractive index difference is significantly smaller than that of a waveguide such as an optical fiber. Therefore, a thickness of 5 μm or more is required to propagate light having a large power while confining it within the first electro-optic crystal layer 11.

<Second Embodiment of Optical Modulation Device>
FIG. 6 is a view showing a second embodiment of the light modulation device according to the present invention. FIG. 6A is a perspective view of the light modulation device, and FIGS. 6B to 6D are views of the light modulation device. It is a figure which shows a light modulation operation | movement typically. The second embodiment is greatly different from the first embodiment in the cross-sectional configuration of the electro-optic crystal layer 11. In other words, the cross section of the electro-optic crystal layer 11 is rectangular in the first embodiment, whereas the cross section of the electro-optic crystal layer 11 is circular in the second embodiment. That is, in the second embodiment, the cylindrical electro-optic crystal layer 11 is provided, and the electro-optic crystal composed of the same material as the electro-optic crystal layer 11 so as to sandwich the electro-optic crystal layer 11 from the vertical direction Y. The layers 12 and 13 are disposed, and the electro-optic crystal layers 12 and 13 are integrated to form a crystal portion 14. Note that the external shape of the electro-optic crystal substrate 15 is a quadrangular prism shape as in the first embodiment. Other configurations are the same as those of the first embodiment. Therefore, about the same structure, the same code | symbol is attached | subjected and description is abbreviate | omitted (this is the same also in the following embodiment).

  In the light modulation device 1B configured as described above, the light Lin is incident on the circular end surface 11a of the electro-optic crystal layer 11, and the potential applied to the first electrode 16a and the second electrode 16b is controlled. As a result, it is switched to the ON state (FIG. 2B), the intermediate state (FIG. 3C), and the OFF state (FIG. 3D), and three-stage light modulation is executed. The same effect can be obtained.

<Third Embodiment of Optical Modulation Device>
FIG. 7 is a view showing a third embodiment of the light modulation device according to the present invention. FIG. 7 (a) is a perspective view of the light modulation device, and FIGS. 7 (b) to (d) are views of the light modulation device. It is a figure which shows a light modulation operation | movement typically. The third embodiment is greatly different from the first embodiment in the structure of the electro-optic crystal substrate 15. In the light modulation device 1 </ b> C according to the third embodiment, the electro-optic crystal layer 12 is formed on the upper surface of the uniaxial electro-optic crystal layer 11 having a quadrangular prism shape extending in the Z direction. An electro-optic crystal layer 13 is formed on the lower surface of the substrate. That is, the third embodiment has a three-layer structure in which the electro-optic crystal layer 11 is sandwiched from the vertical direction Y in a state where the electro-optic crystal layers 12 and 13 are separated from each other in the direction Y. These electro-optic crystal layers 11 to 13 are made of the same material, for example, uniaxial electro-optic crystals such as LN (LiNbO ₃ ) and LT (LiTaO ₃ ), as in the first embodiment. The crystal axis orientation of the electro-optic crystal layer 11 is upward as shown by the arrow in the end face 11a in FIG. 7, while the crystal axis orientation of the electro-optic crystal layers 12 and 13 is in the end faces 12a and 13a in FIG. It is facing down as shown by the arrow. As described above, the crystal axis orientation of the electro-optic crystal layer 11 and the crystal axis orientations of the electro-optic crystal layers 12 and 13 are shifted from each other by 180 ° and are in opposite directions. Other configurations are the same as those of the first embodiment.

  In the light modulation device 1 </ b> C configured as described above, as illustrated in FIG. 7A, the light Lin shaped into a slab is incident on the one end surface 11 a of the electro-optic crystal layer 11. Then, the potential applied to the first electrode 16a and the second electrode 16b is controlled to be in an ON state (FIG. (B)), an intermediate state (FIG. (C), and an OFF state (FIG. (D)). Thus, the three-stage optical modulation is performed, so that the same effect as the first embodiment can be obtained.

<Fourth Embodiment of Light Modulation Device>
FIG. 8 is a view showing a light modulation device according to a fourth embodiment of the present invention. FIG. 8 (a) is a perspective view of the light modulation device, and FIGS. 8 (b) to (d) are views of the light modulation device. It is a figure which shows a light modulation operation | movement typically. The features of the fourth embodiment are the structure of the electro-optic crystal substrate 15 and the electrode structure. Among these, the structure of the electro-optic crystal substrate 15 is the same as that of the third embodiment in that the electro-optic crystal layer 11 is sandwiched from the vertical direction Y with the electro-optic crystal layers 12 and 13 being separated from each other in the direction Y 3. It has a layer structure.

  On the other hand, the electrode structure is different from that of the third embodiment. That is, in the fourth embodiment, the first electrodes 16a are formed on both side surfaces of the electro-optic crystal layer 12 in the left-right direction X orthogonal to both the light propagation direction Z and the up-down direction Y, and in the left-right direction X Second electrodes 16 b are formed on both side surfaces of the electro-optic crystal layer 13. Other configurations are the same as those of the third embodiment.

  In the light modulation device 1D configured in this way, as shown in FIG. 8A, the light Lin shaped into a slab of extraordinary rays polarized in the crystal axis direction is one end face of the electro-optic crystal layer 11 11a. Then, by controlling the potentials applied to the first electrodes 16a and 16a and the second electrodes 16b and 16b, the ON state (FIG. (B)), the intermediate state (FIG. (C) and the OFF state (FIG. Therefore, the same effect as in the first embodiment can be obtained, and in the fourth embodiment, the electrode 16a is formed on the side surface of the electro-optic crystal substrate 15. 16b, the light modulation device 1D can be downsized in the vertical direction Y.

<Fifth Embodiment of Optical Modulation Device>
FIG. 9 is a view showing a fifth embodiment of the light modulation device according to the present invention. This light modulation device 1E can perform light modulation independently for a plurality of channels, and is configured as follows. The electro-optic crystal substrate 15 of the light modulation device 1E has a three-layer structure in which a plate-like electro-optic crystal layer 11 having a thickness of 5 to 100 μm is sandwiched between the electro-optic crystal layers 12 and 13 from the vertical direction Y. Also in the fifth embodiment, the electro-optic crystal layers 11 to 13 are made of the same uniaxial electro-optic crystal as in the third and fourth embodiments, but the electro-optic crystal layer 11 9 is directed upward as indicated by the arrow in the side surface of FIG. 9, while the crystal axis orientation of the electro-optic crystal layers 12 and 13 is directed downward as indicated by the arrow in the side surface of FIG. Yes. As described above, the crystal axis orientation of the electro-optic crystal layer 11 and the crystal axis orientations of the electro-optic crystal layers 12 and 13 are shifted from each other by 180 ° and are in opposite directions.

  The upper surface of the electro-optic crystal substrate 15 thus configured (the upper surface of the electro-optic crystal layer 12) is finished in a horizontal plane parallel to the XZ plane. A plurality (five in this embodiment) of first electrodes 16a are arranged on the upper surface in parallel to each other while being spaced apart from each other in the X direction by a predetermined interval. In the fifth embodiment, each first electrode 16 a extends in parallel with the light propagation direction Z and extends from the (−Z) side end of the electro-optic crystal substrate 15 to the (+ Z) side end. Further, the lower surface of the electro-optic crystal substrate 15 (the lower surface of the electro-optic crystal layer 13) is also finished in a horizontal plane parallel to the XZ plane, and the same number of second electrodes 16b as the first electrodes 16a with respect to the lower surface are the first electrodes 16a. And the electro-optic crystal substrate 15 in a one-to-one relationship. Thus, five pairs of electrodes are formed as shown in FIG. 9B, and a region sandwiched between the electrodes 16a and 16b (hereinafter referred to as “channel region”) in the X direction is formed on the electro-optic crystal substrate 15. It exists side by side. Accordingly, focusing on one channel region, the first electrode 16a is disposed on the upper surface and the second electrode 16b is disposed on the lower surface. Such a configuration is the same as that of the light modulation device 1C of the third embodiment. is there. That is, in the light modulation device 1E according to the fifth embodiment, five configurations equivalent to those of the light modulation device 1C according to the third embodiment are arranged in parallel in the X direction. Then, as shown in FIG. 6A, slab-shaped light Lin having a cross section extending in the X direction of extraordinary rays polarized in the direction of the crystal axis is incident on one end face 11a of the electro-optic crystal layer 11 to form a channel region. To propagate.

  The electrodes 16a and 16b are electrically connected to the potential applying unit 17, and the potential applied from the potential applying unit 17 to the electrodes 16a and 16b can be arbitrarily controlled. For example, the potential applied to the first electrode 16a disposed on the upper surface of the channel region CR1 located at the left end in FIG. 9B is based on the potential applied to the second electrode 16b disposed on the lower surface of the channel region CR1. When a potential is applied to these electrodes 16a and 16b so that the height is higher, the refractive index is distributed in the channel region CR1 as follows. That is, in the channel region CR1, the refractive index of the electro-optic crystal layer 11 located at the center in the vertical direction Y increases by Δne as shown in FIG. On the other hand, the refractive indexes of the electro-optic crystal layers 12 and 13 positioned in the vertical direction of the electro-optic crystal layer 11 in the channel region CR1 are decreased by Δne as shown in FIG. 5E and become (n−Δne). For this reason, the light Lin propagated through the channel region CR1 propagates in the light propagation direction Z in a single mode while being confined in the electro-optic crystal layer 11. Therefore, the intensity of the light Lout emitted from the other end face 11b of the electro-optic crystal layer 11 becomes relatively high as shown in FIG. Further, the channel regions located second and third from the left end in FIG. 9B are also in the “ON state” as in the channel region CR1.

  When the same potential is applied to the first electrode 16a disposed on the upper surface of the channel region CR4 located fourth from the left end in FIG. 9B and the second electrode 16b disposed on the lower surface, In the channel region CR4, the entire electro-optic crystal substrate 15 has a refractive index n as shown in FIGS. For this reason, the intensity of the light Lout emitted from the other end face 11b of the electro-optic crystal layer 11 is lower than that in the ON state as shown in FIG.

  Further, the potential applied to the first electrode 16a disposed on the upper surface of the channel region CR5 located at the right end in FIG. 9B is the potential applied to the second electrode 16b disposed on the lower surface of the channel region CR5. When a potential is applied to these electrodes 16a and 16b so as to be lower, the refractive index is distributed in the channel region CR5 as follows. That is, in the channel region CR5, the refractive index of the electro-optic crystal layer 11 located at the center in the up-down direction Y decreases by Δne as shown in FIG. On the other hand, in the channel region CR5, the refractive indexes of the electro-optic crystal layers 12 and 13 positioned in the vertical direction of the electro-optic crystal layer 11 increase by Δne as shown in FIG. 5E and become (n + Δne). Therefore, the light Lin propagating through the channel region CR5 spreads so as to be sucked into the electro-optic crystal layers 12 and 13, and the intensity of the light Lout emitted from the other end face 11b of the electro-optic crystal layer 11 is extremely reduced. However, the light intensity is lower than that in the intermediate state and is close to zero, that is, the “OFF state”.

  As described above, according to the fifth embodiment, five first electrodes 16a are provided on the surface of the electro-optic crystal layer 12 so as to be separated from each other in the X direction, and the second electrodes 16b are provided so as to be separated from each other in the X direction. Five are provided on the surface of the optical crystal layer 13 to provide five electrode pairs, and the potential applied to each electrode pair is controlled independently. Therefore, light modulation can be performed independently for each electrode pair. That is, the light modulation device 1E configured as shown in FIG. 9 can perform spatial light modulation of five channels. Of course, since each channel basically has the same configuration and operation as the optical modulation device 1C of the third embodiment, the same effects as in the third embodiment, that is, high power resistance performance and light with short wavelength light. It has the effect of high damage performance and high-speed modulation.

  Further, in the multi-channel optical modulation device 1E according to the fifth embodiment, since there is no need to provide a special restriction for adjacent channel regions, the distance between the channels can be reduced, and a small, high-density multi-channel device can be provided. Channel drive is possible.

<Exposure device>
FIG. 10 is a view showing an embodiment of an exposure apparatus equipped with a light modulation device according to the present invention. FIG. 10 (a) is a view showing a configuration in the YZ plane, and FIG. 10 (b) is a light modulation device. It is a perspective view which shows the arrangement | positioning relationship between an aperture and an aperture. The exposure apparatus 100A is an apparatus that modulates the light Lin emitted from the single light source unit 173 by the light modulation device 1A according to the first embodiment and irradiates the exposed surface ES such as the substrate surface. The exposure apparatus 100A includes a light source unit 173 configured by a semiconductor laser or the like that emits light having a predetermined wavelength (for example, 633 nm). The light source unit 173 has a collimator lens (not shown), and an illumination optical system composed of a single lens having a positive power in which light emitted from a semiconductor laser or the like is converted into parallel light via a collimator lens. 174 is incident. In this exposure apparatus 100A, since light modulation is performed using the light modulation device 1A, the incident light Lin is a linearly polarized laser and the plane of polarization is parallel to the crystal axes of the electro-optic crystal layers 11 to 13 of the light modulation device 1A. It is suitable for. Then, the light Lin emitted from the light source unit 173 enters the one end face 11a of the electro-optic crystal layer 11 of the light modulation device 1A via the illumination optical system 174.

In the exposure apparatus 100A, the following configuration is specifically adopted as the light source unit 173 and the light modulation device 1A. As the light source of the light source unit 173, a helium-neon (He-Ne) laser that generates linearly polarized light having a wavelength λ of 633 nm is used. Further, the electro-optic crystal layer 11 and the crystal part 14 constituting the electro-optic crystal substrate 15 of the light modulation device 1A are formed of LN (LiNbO ₃ ). Further, both end faces 11a and 11b of the electro-optic crystal layer 11 are 30 μm square, whereas the thickness of the crystal part 14 is 15 μm. Therefore, the gap g (see FIG. 1C) between the first electrode 16a and the second electrode 16b is 60 μm. The length of the electro-optic crystal substrate 15 in the Z direction is 20 mm. In this electro-optic crystal substrate 15, as in the first embodiment, the crystal axis orientation of the electro-optic crystal layer 11 is upward as indicated by the arrow in the end face 11a of FIG. 10A, and the crystal portion 14 is downward. It has become. Thus, in this embodiment, since helium-neon laser light having a wavelength of 633 nm is used as the incident light Lin, the Pockels constant r33 = 30.8 × 10 ⁻⁶ (μm / V) of the LN crystal and Refractive index ne = 2.200.

When +5 volts is applied to the first electrode 16a and -5 volts is applied to the second electrode 16b, the electric field is applied downward from above. Therefore, since the refractive index change amount Δne = 2.73 × 10 ^{−5 according to} Equation 3, the refractive index of the electro-optic crystal layer 11 increases by Δne, whereas the peripheral portion of the electro-optic crystal layer 11, that is, In the crystal portion 14, the refractive index is decreased by Δne to be “ON”, and the electro-optic crystal layer 11 guides the incident light Lin. The light Lin is emitted from the end face 11b of the electro-optic crystal layer 11 as propagating light Lout. When a reverse voltage, that is, -5 volts is applied to the first electrode 16a and +5 volts is applied to the second electrode 16b, the sign of the refractive index change is reversed between the electro-optic crystal layer 11 and the crystal portion 14, and the electro-optic crystal layer 11 enters the crystal portion 14 and becomes non-propagating light L ′ and is emitted from the electro-optic crystal substrate 15.

  On the emission side of the light modulation device 1A (the right-hand side in FIG. 10A), an imaging lens as an optical system that forms an exposure spot by forming an image of the light Lout modulated by the light modulation device 1A on the exposure surface ES 176 is arranged. Further, as described above, the light modulation device 1A emits the propagation light Lout and the non-propagation light L ′ according to the potential applied to the electrodes 16a and 16b. Therefore, in the exposure apparatus 100A according to the present embodiment, the aperture plate 177 is disposed between the light modulation device 1A and the imaging lens 176. An aperture 177a is formed at the center of the aperture plate 177, and only the propagating light Lout emitted from the light modulation device 1A is allowed to pass through, and the non-propagating light L ′ is blocked by the aperture plate 177. Accordingly, when +5 volts is applied to the first electrode 16a and -5 volts is applied to the second electrode 16b to turn on the light modulation device 1A, the propagation light Lout having high light intensity is applied to the exposed surface ES. Irradiated. Further, when both the electrodes 16a and 16b are set to the same potential and the light modulation device 1A is set to the “intermediate state”, the propagation surface Lout having a light intensity lower than that of the “ON state” is irradiated to the exposed surface ES. Further, when -5 volts is applied to the first electrode 16a and +5 volts is applied to the second electrode 16b to turn off the light modulation device 1A, most of the light Lin incident on the electro-optic crystal layer 11 is crystallized. The light is emitted as non-propagating light L ′ from the end surface of the portion 14 and is shielded by the aperture plate 177 so that the irradiation amount of the propagating light Lout to the exposed surface ES becomes zero.

  As described above, by using the light modulation device 1A having high power resistance, a light source having a relatively high power can be used for the light source unit 173, and the exposure efficiency can be increased. In addition, since the light modulation device 1A has high optical damage performance with short-wavelength light, the wavelength range that can be used in the exposure apparatus 100A is widened and excellent in versatility. Furthermore, since light modulation can be performed with a potential difference of about 10 V, the modulation speed can be increased to further increase the exposure efficiency.

  The light modulation device 1A employed in the exposure apparatus 100A is significantly different from the modulation principle in a conventional light modulation device, for example, the apparatus described in Non-Patent Document 1, and has little wavelength dependency. Therefore, a plurality of lights having different wavelengths can be combined and incident on the light modulation device 1A to modulate these lights at a time. In addition, since the light modulation device 1A can favorably modulate even broad light having a wide wavelength range (half-value width), it is also favorable for an exposure apparatus that performs exposure processing using such light. Can be applied.

  Further, in the exposure apparatus 100A, light modulation is performed using the light modulation device 1A. However, similar effects can be obtained by using the light modulation devices 1B to 1D shown in FIGS. Further, the exposure apparatus 100A performs the exposure process with a single light, but the efficiency of the exposure process can be further improved by providing a plurality of combinations of the light source unit 173 and the light modulation device 1A (or 1B to 1D). it can. Further, by using the multi-channel light modulation device 1E, it is possible to perform multi-exposure while using a single light source. Hereinafter, another embodiment of the exposure apparatus will be described with reference to FIGS.

  11 is a view showing another embodiment of the exposure apparatus equipped with the light modulation device according to the present invention, FIG. 12 is a perspective view showing the main body of the exposure apparatus shown in FIG. 11, and FIG. It is a block diagram which shows the electric structure of the exposure apparatus of this. This exposure apparatus 100B is an apparatus for drawing a pattern by irradiating light onto the surface of a substrate W such as a semiconductor substrate or a glass substrate having a photosensitive material applied to the surface, and the light is emitted from the multichannel according to the fifth embodiment. The light modulation device 1E is used for light modulation, and a pattern is drawn using the modulated light. Hereinafter, after describing the overall configuration of the exposure apparatus 100B, the configuration and operation for modulating light using the light modulation device 1E will be described in detail.

  In this exposure apparatus 100B, each part of the apparatus is arranged inside a main body formed by attaching a cover 102 to the main body frame 101 to form the main body, and the outside of the main body (in this embodiment, FIG. 11). The substrate storage cassette 110 is disposed on the right hand side of the main body as shown in FIG. The substrate storage cassette 110 stores an unprocessed substrate W to be subjected to exposure processing, and is loaded into the main body by a transfer robot 120 disposed inside the main body. Further, after the exposure process (pattern drawing process) is performed on the unprocessed substrate W, the substrate W is unloaded from the main body by the transfer robot 120 and returned to the substrate storage cassette 110.

  In this main body, as shown in FIGS. 11 and 12, the transfer robot 120 is arranged at the right hand end inside the main body surrounded by the cover 102. A base 130 is disposed on the left hand side of the transfer robot 120. One end side area (the right hand side area in FIGS. 11 and 12) of the base 130 is a substrate transfer area for transferring the substrate W to and from the transfer robot 120, whereas the other end side area (Left-hand side region in FIGS. 11 and 12) is a pattern drawing region for pattern drawing on the substrate W. On the base 130, a head support 140 is provided at the boundary position between the substrate delivery area and the pattern drawing area. In the head support portion 140, two leg members 141 and 142 are erected upward from the base 130, and a beam member 143 is laterally provided so as to bridge the top portions of the leg members 141 and 142. Yes. Then, as shown in FIG. 11, the camera (imaging unit) 150 is fixed to the side of the pattern drawing area of the beam member 143 and the surface of the substrate W (the drawing surface and the exposed surface) held on the stage 160 is imaged. It is possible.

  The stage 160 is moved on the base 130 by the stage moving mechanism 161 in the X direction, the Y direction, and the θ direction. That is, the stage moving mechanism 161 has a Y-axis drive unit 161Y (FIG. 13), an X-axis drive unit 161X (FIG. 13), and a θ-axis drive unit 161T (FIG. 13) stacked on the upper surface of the base 130 in this order. The stage 160 is moved and positioned two-dimensionally in a horizontal plane. Further, the stage 160 is rotated around the θ axis (vertical axis) to adjust the relative angle with respect to the optical head 170 described later for positioning. As such a stage moving mechanism 161, an XY-θ axis moving mechanism that has been widely used conventionally can be used.

  Further, the optical head 170 is mounted on the pattern drawing area side of the head support unit 140 configured in this manner so as to be movable in the vertical direction, and the head moving mechanism 171 is activated in response to an operation command from the exposure control unit 181. By doing so, the distance from the substrate W held on the stage 160 described later can be adjusted with high accuracy. The optical head 170 is equipped with the light modulation device 1E according to the fifth embodiment and irradiates the substrate W with light, and the configuration and operation thereof will be described in detail later.

  Also, two leg members 144 are erected on the opposite end of the base 130 on the side opposite to the board delivery side (the left-hand side end in FIGS. 11 and 12). A box 172 containing the illumination optical system of the optical head 170 is provided so as to bridge the beam member 143 and the top of the two leg members 144, and covers the pattern drawing region of the base 130 from above. Yes. Therefore, even if the downflow supplied into the clean room in which the exposure apparatus 100B is installed is drawn into the main body, a space SP in which the downflow is not supplied is formed in the pattern drawing area.

  Therefore, in the exposure apparatus 100B according to the present embodiment, a gas blowing unit that blows out the temperature-controlled gas toward the space SP sandwiched between the stage 160 and the box 172 of the optical head 170 on the side opposite to the space SP of the space SP. 190 is arranged. In this embodiment, the two gas blowing parts 190 are attached up and down so that the cover 102 which comprises the left-hand side wall of a main-body part may be penetrated. These gas blowing units 190 are connected to an air conditioner 191 and operate according to a command from the exposure control unit 181 to blow out the air temperature-controlled by the air conditioner 191 toward the space SP. Thereby, the temperature-controlled gas blown out from the gas blowing unit 190 flows sideways and passes through the space SP. As a result, the atmosphere of the space SP is switched, and the temperature change in the pattern drawing area is suppressed. In addition, the air that has passed through the space SP flows into the transfer robot 120 in this way, but in this embodiment, an exhaust port 192 is provided in the lower portion of the transfer robot 120 and the exhaust port 192 is air-conditioned via the pipe 193. Connected to the device 191. Therefore, by providing the exhaust port 192, the atmosphere surrounding the transfer robot 120 is exhausted, and a downward airflow, that is, a downflow is formed in the atmosphere. Accordingly, it is possible to effectively prevent the particles from rising and scattering by the transfer robot 120.

  Next, the configuration and operation of the optical head 170 will be described. In this embodiment, the optical head 170 is attached to the head support portion 140 so as to be movable in the vertical direction Z as described above, and light is applied to the substrate W moving immediately below the optical head 170. The substrate W held on the stage 160 is exposed by being reflected and a pattern is drawn. In this embodiment, the optical head 170 can simultaneously irradiate light in a plurality of channels in the X direction, and the X direction corresponds to the “sub-scanning direction”. Further, by moving the stage 160 in the Y direction, a pattern can be drawn two-dimensionally on the substrate W, and the Y direction corresponds to the “main scanning direction”.

  FIG. 14 is a diagram showing the internal configuration of the optical head in a simplified manner. FIG. 14A is an optical head when the optical head 170 is viewed from above along the optical axis OA and the sub-scanning direction X of the optical head 170. 170B shows the internal configuration of the optical head 170 when the optical head 170 side is viewed from the side along the main scanning direction Y. FIG.

  The optical head 170 shown in FIG. 14 has a light source unit 173 configured by a semiconductor laser or the like that emits light of a predetermined wavelength. The light source unit 173 has a collimator lens (not shown), and light emitted from a semiconductor laser or the like is converted into parallel light through the collimator lens and enters the illumination optical system 174.

  The illumination optical system 174 is composed of three cylindrical lenses 174a to 174c, and the light Lin emitted from the light source unit 173 passes through the cylindrical lenses 174a to 174c in this order, and the electro-optic crystal layer of the light modulation device 1E. 11 is incident on one end face 11a. Of these, the cylindrical lens 174a has a negative power only in the X direction, and the light passing through the cylindrical lens 174a changes from a circular cross section perpendicular to the optical axis OA to an ellipse having a longer length in the X direction. . On the other hand, with respect to the optical axis OA and the Y direction perpendicular to the X direction, the width of the light beam cross section of the light Lin that has passed through the cylindrical lens 174a is (almost) constant.

  The cylindrical lens 174b has a positive power only in the X direction, and the light Lin that has passed through the cylindrical lens 174a is shaped by the cylindrical lens 174b. That is, the light Lin that has passed through the cylindrical lens 174b is formed into an elliptical shape having a constant cross-section that is long in the X direction, and is incident on the cylindrical lens 174c.

  The cylindrical lens 174c has a positive power only in the Y direction. When attention is paid only to the Y direction, the light Lin that has passed through the cylindrical lens 174c is condensed as shown in FIG. 14B. The light enters the one end face 11 a of the electro-optic crystal layer 11. Regarding the X direction, as shown in FIG. 14A, the light Lin from the cylindrical lens 174c is incident on the one end face 11a of the electro-optic crystal layer 11 as parallel light. Since the configuration and operation of the light modulation device 1E have already been described, description thereof is omitted here.

  On the emission side (right hand side in FIG. 14) of the light modulation device 1E, a slit plate 178, a cylindrical lens 175 having a positive power only in the Y direction, and a schlieren optical system 176 are arranged in this order.

  FIG. 15 is a perspective view of the slit plate. At the center of the slit plate 178, a slit 178a that allows only the propagation light Lout emitted from the end face 11b of the electro-optic crystal layer 11 to pass is provided. On the other hand, light that cannot be guided through the electro-optic crystal layer 11 (non-guided light), that is, non-propagating light L ′ is emitted from the end face of the crystal portion 14 as shown by the broken line in FIG. It is shielded by a plate 178. Therefore, only the propagation light Lout is incident on the cylindrical lens 175.

This cylindrical lens 175 has a positive power only in the Y direction, and the propagation light Lout emitted from the other end surface 11b of the electro-optic crystal layer 11 of the light modulation device 1E is as shown in FIG.
The light is made substantially parallel with respect to the Y direction by the cylindrical lens 175 and enters the schlieren optical system 176. The schlieren optical system 176 includes a lens 176a, an aperture plate 176b having an aperture 176b1, and a lens 176c. The propagating light Lout passes through the aperture 176b1 and reaches the surface of the substrate W. In this embodiment, the aperture plate 176b is provided. However, this is not an essential configuration, and the aperture plate 176b may be omitted.

  As described above, in this embodiment, the non-propagating light L ′ is shielded by the slit plate 178, while the propagating light Lout modulated by controlling the potential for each electrode pair is the surface (exposed surface) of the substrate W. Is irradiated. In this way, optical modulation is performed for each of the five channels. For example, as shown in FIG. 9B, when the first to third channels are set to the “ON state” by controlling the potentials applied to the electrodes 16a and 16b, the electro-optic crystal layer 11 includes these layers. Light Lin is guided in a region corresponding to the channel, is emitted from the other end surface 11 b of the electro-optic crystal layer 11, and is irradiated onto the surface of the substrate W. As a result, exposure is performed in a spot shape corresponding to the first to third channels. Further, in FIG. 9B, the fourth channel is in the “intermediate state”, so that the light Lout is emitted from the other end surface 11b of the electro-optic crystal layer 11 corresponding to the fourth channel to the surface of the substrate W. Irradiated. However, since the amount of light is very small, in FIG. 14 (a), the exposure positions of the first to third channels are shown as black circle spots, while the exposure position of the fourth channel is shown as a satin pattern spot. The figure shows that the exposure light quantity in the four channels is lower than the exposure light quantity in the first to third channels. Further, in FIG. 9B, since the fifth channel is in the “OFF state”, the light Lout is hardly emitted from the other end face 11b of the electro-optic crystal layer 11 corresponding to the channel, and therefore corresponds to the fifth channel. No spot is formed.

  Thus, in this embodiment, the lens 176a, the aperture plate 176b, and the lens 176c constitute a so-called Schlieren optical system 176. This schlieren optical system 176 has the same arrangement as the double-sided telecentric optical system. As shown in FIG. 14, even when the substrate W is exposed by the optical head 170 having a plurality of channels, the exposure surface (the surface of the substrate W). ), The propagation light Lout of each channel is perpendicular, and is not affected by a change in magnification with respect to a change in the focus direction Z of the exposure surface (the surface of the substrate W). As a result, highly accurate exposure is possible.

  Note that the exposure apparatus 100B configured as described above includes a computer 200 for controlling the entire apparatus. The computer 200 includes a CPU, a memory 201, and the like, and is arranged in an electrical rack (not shown) together with the exposure control unit 181. In addition, the rasterization unit 202, the expansion / contraction rate calculation unit 203, the data correction unit 204, and the data generation unit 205 are realized by the CPU in the computer 200 performing arithmetic processing according to a predetermined program. For example, pattern data corresponding to one LSI is data generated by an external CAD or the like, and is prepared in advance in the memory 201 as LSI data 211. Based on the LSI data 211, the LSI pattern is as follows. Is drawn on the substrate W.

  The rasterizing unit 202 divides and rasterizes the unit area indicated by the LSI data 211, generates raster data 212, and stores it in the memory 201. Thus, after preparing the raster data 212 or in parallel with the preparation of the raster data 212, the unprocessed substrate W stored in the cassette CS as described above is carried out by the transfer robot 120 and placed on the stage 160. Is done.

  Thereafter, the stage 160 is moved to a position immediately below the camera 150 by the stage moving mechanism 161, and the alignment marks (reference marks) on the substrate W are sequentially positioned at the imageable positions of the camera 150, and mark imaging by the camera 150 is executed. Is done. The image signal output from the camera 150 is processed by an image processing circuit in the electrical rack, and the position of the alignment mark on the stage 160 is accurately determined. Then, the θ-axis drive unit 161T operates based on these pieces of position information, and the stage 160 is slightly rotated about the vertical axis to be aligned (positioned) in a direction suitable for pattern drawing on the substrate W. Here, the alignment may be performed after the stage 160 is moved to a position directly below the optical head 170.

  The stretch rate calculation unit 203 illustrated in FIG. 13 acquires the alignment mark position on the substrate W and the correction amount of the orientation of the substrate W obtained by the image processing circuit, the alignment mark position after alignment, and The expansion / contraction ratio of the substrate W with respect to the main scanning direction Y and the sub-scanning direction X (that is, the expansion ratio of the main surface) is obtained.

  On the other hand, the data correction unit 204 acquires the raster data 212 and corrects the data based on the expansion / contraction rate that is the detection result of expansion / contraction. For this data correction, for example, the method described in Japanese Patent No. 40020248 can be adopted. When the data correction of one divided area is completed, the corrected raster data 212 is sent to the data generation unit 205. . The data generation unit 205 generates drawing data corresponding to the changed divided area, that is, data corresponding to one stripe.

  The drawing data generated in this way is sent from the data generation unit 205 to the exposure control unit 181, and the exposure control unit 181 controls each part of the potential applying unit 17, the head moving mechanism 171, and the stage moving mechanism 161, thereby creating one stripe. Minutes are drawn. The exposure operation is performed by controlling the potential applied to the electrodes 16a and 16b by the potential applying unit 17 as described above. When the exposure recording for one stripe is completed, the same processing is performed for the next divided region, and drawing for each stripe is repeated. Thus, when drawing of all the stripes on the substrate W is completed and drawing of a desired pattern on the surface of the substrate W is completed, the stage 160 moves to the substrate delivery position with the drawn substrate W placed thereon, and then the transfer robot. The substrate W is returned to the cassette CS by 120, the next substrate W is taken out, and a series of processes similar to those described above are repeated. Further, when the pattern drawing on all the substrates W stored in the cassette CS is completed, the cassette CS is unloaded from the exposure apparatus 100B.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the first to fourth embodiments, electrodes are formed on the entire surface and side surfaces of the electro-optic crystal layers 12 and 13. In the fifth embodiment, the first electrode 16 a and the second electrode 16 b are extended from the (−Z) side end of the electro-optic crystal substrate 15 to the (+ Z) side end. However, the formation range of the electrodes 16a and 16b is not limited to this.

  In the embodiment shown in FIG. 11, the head moving mechanism 171 is provided in the optical head 170 equipped with the light modulation device according to the present invention to adjust the distance between the substrate W and the optical head 170. However, the stage moving mechanism 161 may be provided with an elevating drive unit so that the distance can be adjusted. Further, the configuration for moving the substrate W relative to the optical head 170 is not limited to the above embodiment. That is, the light modulation device according to the drawing (LSI) data while moving the position where the plurality of lights Lout emitted from the light modulation device 1E are irradiated to the substrate W held on the stage 160 relative to the substrate W. The present invention can be applied to all pattern drawing apparatuses that draw a pattern by controlling 1E.

  The recording material for drawing the pattern may be a photosensitive material such as a printed wiring board or a semiconductor substrate, or may be another photosensitive material, and is a material that reacts to heat due to light irradiation. It may be.

  Furthermore, the light modulation devices 1A to 1E configured as described above may be used for applications other than pattern drawing, and in this case, the object to be irradiated with light may be other than the recording material.

DESCRIPTION OF SYMBOLS 1A-1E ... Light modulation device 11 ... 1st electro-optic crystal layer 12 ... 2nd electro-optic crystal layer 13 ... 4th electro-optic crystal layer 11a ... (1st electro-optic crystal layer) one end surface 11b ... (1st electricity The other end face (of the optical crystal layer) 15 ... electro-optical crystal substrate 16a ... first electrode 16b ... second electrode 17 ... potential application unit 100A, 100B ... exposure device 173 ... light source unit 175 ... cylindrical lens (optical system)
176 ... Schlieren optical system, imaging lens (optical system)
Lin ... Incident light Lout ... Propagating light L '... Non-propagating light W ... Substrate

Claims (10)

A second electro-optic crystal having a crystal axis orientation different from that of the first electro-optic crystal layer, wherein the first electro-optic crystal layer that guides light incident from the one end face in the first direction and emits the light from the other end face An electro-optic crystal substrate configured to be sandwiched between a layer and a third electro-optic crystal layer from a second direction orthogonal to the first direction;
A first electrode provided on a surface of the second electro-optic crystal layer;
A second electrode provided on the surface of the third electro-optic crystal layer;
The potential applied to the first electrode and the second electrode is controlled to change the refractive indexes of the first electro-optic crystal layer, the second electro-optic crystal layer, and the third electro-optic crystal layer with respect to the incident light. And a potential applying unit that changes the intensity of the light emitted from the other end face.   The second electro-optic crystal layer and the third electro-optic crystal layer are integrally formed to form a crystal part, and the crystal part surrounds the first electro-optic crystal layer in a cross section with respect to the first direction. 2. The light modulation device according to 1.   The light modulation device according to claim 1, wherein the second electro-optic crystal layer and the third electro-optic crystal layer are formed apart from each other in the second direction.   4. The crystal axis orientation of the first electro-optic crystal layer and the crystal axis orientations of the second electro-optic crystal layer and the third electro-optic crystal layer are shifted from each other by 180 °. The light modulation device according to item.   5. The crystal axis orientation of the first electro-optic crystal layer and the crystal axis orientations of the second electro-optic crystal layer and the third electro-optic crystal layer are orientations parallel to the second direction. Light modulation device.   6. The light modulation device according to claim 1, wherein the first electro-optic crystal layer, the second electro-optic crystal layer, and the third electro-optic crystal layer are the same type of crystal.   The length of the first electro-optic crystal layer in the first direction is not less than 1 mm and not more than 50 mm, and the thickness of the first electro-optic crystal layer in the second direction is not less than 5 μm and not more than 100 μm. The light modulation device according to any one of claims. The second electro-optic crystal layer has a first surface perpendicular to the second direction, and the third electro-optic crystal layer has a second surface perpendicular to the second direction;
N (n ≧ 2) first electrodes are provided on the first surface so as to be spaced apart from each other in the third direction orthogonal to the first direction and the second direction, and the second electrode is provided in the third direction. N pairs of electrode pairs, which are provided on the second surface so as to be spaced apart from each other in the direction and are constituted by the first electrode and the second electrode facing each other across the first electro-optic crystal layer Provided,
The light modulation device according to claim 1, wherein the potential applying unit independently controls a potential applied to the n sets of electrode pairs.   The light modulation device according to claim 8, wherein the n first electrodes and the n second electrodes extend in parallel with the first direction. An exposure apparatus that irradiates and exposes an exposed surface with light,
The light modulation device according to any one of claims 1 to 9,
A light source unit that makes light incident on one end face of the first electro-optic crystal layer;
An exposure apparatus comprising: an optical system that guides the modulated light modulated by the light modulation device and emitted from the other end face of the first electro-optic crystal layer to the exposed surface.

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