JP5328512B2 - Exposure equipment - Google Patents

Abstract

PURPOSE: An exposure head and exposure device are provided to maintain a high resolution and deep depth focus by performing multi focus exposure. CONSTITUTION: An exposure head comprises: a light source(66) for irradiating light; a spatial light modulator which generates a plurality of beams corresponding to every pixel part by modulating irradiated light based on image data; a light focusing optical system for focusing plural beams; an image-forming optical system(80,82) which forms the beams on photosensitive materials; and parallel flat panels(10).

Description

The present invention relates to an exposure apparatus .

  Conventionally, various exposure heads for exposing a photosensitive material using light modulated by a spatial light modulation element based on image data and exposure apparatuses for scanning the exposure head to form an image pattern on the photosensitive material are known. It has been. The spatial light modulation element is formed by arranging a large number of pixel units that modulate irradiated light according to control signals. An example of the spatial light modulation element is a digital micromirror device (DMD: registered trademark). The DMD is a mirror device in which a large number of micromirrors that change the angle of a reflecting surface according to a control signal are two-dimensionally arranged on a semiconductor substrate such as silicon.

  Patent Document 1 includes a spatial light modulation element in which a large number of pixel portions that modulate irradiated light according to control signals are arranged in parallel, and is moved relative to the photosensitive material to be in the same position of the photosensitive material. In the exposure head that performs multiple exposure with light from the plurality of pixel portions, the light from each pixel portion of the spatial light modulation element is condensed on the optical path between the spatial light modulation element and the photosensitive material. An exposure head comprising: a microlens array in which microlenses are arranged in an array; and a focal length of at least two microlenses among the microlenses used for multiple exposure at the same position is different. Has been.

  Further, in Patent Document 2, in a projection lens system including at least one diffractive optical element, one of the diffractive optical elements is composed of a plurality of zones, and a light beam transmitted through the plurality of zones is in the optical axis direction. A projection lens system is described in which the plurality of zones have different imaging effects so as to form images at at least two slightly different positions.

JP 2007-33973 A JP-A-6-319442

  The inventions described in Patent Document 1 and Patent Document 2 are all intended to increase the depth of focus. However, since the exposure head described in Patent Document 1 uses two or more types of microlenses having different focal lengths, the convergence angle of the light beam used for multiple exposure is different and the beam waist diameter is also different. For this reason, the exposure head and the like described in Patent Document 1 are not suitable for high-definition exposure because it becomes difficult to increase the depth of focus as the resolution increases.

  In addition, the projection lens system described in Patent Document 2 obtains a light beam that forms an image at a plurality of positions using a diffractive optical element, and the optical axis direction of the obtained light beam is different. Not suitable for multiple exposure. Further, a diffractive optical element having a special structure composed of a plurality of zones is required.

The present invention has been made to solve the above-described problems, and an object of the present invention is to maintain a high resolution and obtain a deep depth of focus by performing multifocal exposure with a light beam having the same focal length. An object of the present invention is to provide an exposure apparatus that can perform the above.

In order to achieve the above object, an invention according to claim 1 is configured to include a light source that emits light and a plurality of pixel portions arranged in a two-dimensional manner, and each of the plurality of pixel portions is the light source. A spatial light modulator that modulates the light emitted from the light according to the image data and generates a plurality of light beams corresponding to each of the plurality of pixel units, and a plurality of light beams generated by the spatial light modulator A condensing optical system for condensing each of the plurality of light beams, an imaging optical system for forming an image of each of the plurality of light beams collected by the condensing optical system on a photosensitive material, A plurality of light beams are disposed between the image optical system and disposed on the optical path of the plurality of light beams generated by the spatial light modulation element so as to intersect the optical axis, and have different focal positions. Parallel plates having a plurality of portions having different thicknesses, and a plurality of An optical head, a moving means for relatively moving in the sub-scanning direction crossing the main scanning direction of the plurality of exposure heads relative to the photosensitive material to be exposed in the main scanning direction, in response to said characteristics of said photosensitive material sub By setting a plurality of focal positions in the scanning direction , a plurality of photosensitive materials having the same focal length and different focal positions with respect to the photosensitive material by the relative movement in the sub-scanning direction by the moving unit. An exposure apparatus comprising: control means for controlling the spatial light modulator and the moving means so that multiple exposure is performed with a light beam.

The control means controls the spatial light modulation element and the moving means so that the photosensitive material is subjected to multiple exposure in order from the back side when the photosensitive material has a characteristic that the light transmittance is reduced by exposure. You may make it do. In addition, when the photosensitive material has a characteristic that the light transmittance increases by exposure, the control means controls the spatial light modulator and the moving means so that the photosensitive material is sequentially exposed from the surface side. You may make it control. Further, when the photosensitive material has a characteristic that the light transmittance is reduced by exposure, the control unit is configured to perform the multiple exposure of the photosensitive material in order from the back side, and the spatial light modulator and the moving unit. And controlling the spatial light modulation element and the moving means so that the photosensitive material is exposed in order from the surface side when the photosensitive material has a characteristic that the light transmittance is increased by exposure. You may make it switch as follows.

Further, the plurality of portions of the parallel plate are formed with different thicknesses so as to have different focal positions in the sub-scanning direction , and have a constant thickness so that the focal position is constant in the main scanning direction. It may be formed.

In the above exposure apparatus, the plurality of portions of the parallel plate have an arrangement in which the photosensitive material is exposed in order from the back side when the photosensitive material has a characteristic that the light transmittance is reduced by exposure. In the case of having a characteristic of increasing the transmittance, it may be formed to have different thicknesses stepwise in the sub-scanning direction so that an array is sequentially exposed from the surface side.

  In the above exposure head and exposure apparatus, it is preferable to use a reflective spatial light modulation element having a micromirror as a pixel portion as the spatial light modulation element.

According to the present invention, there is an effect that it is possible to provide an exposure apparatus capable of maintaining a high resolution and obtaining a deep focal depth by performing multifocal exposure with light beams having the same focal length.

According to the fifth aspect of the present invention, multiple exposure is performed with a plurality of light beams having the same focal length and different focal positions in the relative movement direction (sub-scanning direction) of the exposure head. Since the focal position is constant in the intersecting direction (main scanning direction), there is an effect that exposure can be performed with substantially uniform light in the main scanning direction.

1 is a perspective view showing a schematic configuration of an exposure apparatus according to a first embodiment. It is a perspective view which shows the structure of a scanner typically. (A) is a top view which shows a mode that the exposed area | region is formed in the photosensitive material, (B) is a schematic diagram which shows the arrangement | sequence of the exposure area by each exposure head. It is a perspective view which shows schematic structure of an exposure head. It is a figure for demonstrating a structure and operation | movement of a mirror device. (A) shows a state tilted to + α degrees when the micromirror is on, and (B) shows a state tilted to −α degrees when the micromirror is off. It is sectional drawing along the optical axis for demonstrating the structure of an exposure head in detail. It is a perspective view which shows the shape of a parallel plate typically. (A)-(C) are schematic diagrams explaining the reason why the depth of focus is expanded by multifocus exposure. It is a schematic diagram which shows the block area | region in the exposure area which is a two-dimensional image obtained by one mirror device, and an exposure area. (A)-(C) are the schematic which shows the mode of the time-dependent change of the multiple exposure by the laser beam from which a focus position differs. It is sectional drawing along the optical axis for demonstrating in detail the structure of the exposure head which concerns on 2nd Embodiment. (A)-(C) are the schematic which shows the mode of the time-dependent change of the multiple exposure by the laser beam from which a focus position differs. (A)-(C) are sectional drawings along the optical axis which show the modification of the shape and arrangement | positioning of a parallel plate. (A) And (B) is the schematic which shows the example of application to a level | step difference board | substrate. It is sectional drawing along the optical axis which shows the modification which enabled the parallel plate to move. It is sectional drawing along the optical axis which shows the modification using the parallel plate which added the aperture array.

  An exposure head and an exposure apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

<First Embodiment>
(Overall configuration of exposure apparatus)
First, the overall configuration of the exposure apparatus of the present embodiment will be described.

  FIG. 1 is a perspective view showing a schematic configuration of the exposure apparatus of the present embodiment. As shown in FIG. 1, the exposure apparatus 100 according to the present embodiment includes a stage 152 as a flat plate-like moving unit that holds and holds a photosensitive material 150 on the surface. Two guides 158 extending along the stage moving direction are installed on the upper surface of the thick plate-like installation table 156 supported by the four legs 154. The stage 152 is arranged so that the longitudinal direction thereof faces the stage moving direction, and is supported by a guide 158 so as to be reciprocally movable. This exposure apparatus is provided with a stage driving device (not shown) that drives a stage 152 as sub-scanning means along a guide 158.

  A U-shaped gate 160 is provided at the center of the installation table 156 so as to straddle the movement path of the stage 152. Each of the ends of the U-shaped gate 160 is fixed to both side surfaces of the installation table 156. On one side of the gate 160, a scanner 162 serving as a scanning exposure unit is provided. In addition, a plurality of (for example, two) sensors 164 that detect the front and rear ends of the photosensitive material 150 are provided on the other side of the gate 160. The scanner 162 and the sensor 164 are respectively attached to the gate 160 and fixedly arranged above the moving path of the stage 152. Therefore, as the stage 152 moves, the scanner 162 and the sensor 164 move relative to the photosensitive material 150. Note that the stage driving device (not shown), the scanner 162, and the sensor 164 are connected to a controller (not shown) that controls them.

(Configuration of scanning exposure unit)
Next, the configuration of the scanner that is the scanning exposure unit of the exposure apparatus will be described.

FIG. 2 is a perspective view schematically showing the configuration of the scanner. FIG. 3A is a plan view showing a state in which exposed regions are formed on the photosensitive material, and FIG. 3B is a schematic diagram showing an arrangement of exposure areas by each exposure head. As shown in FIGS. 2 and 3B, the scanner 162 includes a plurality of exposure heads 166. The plurality of exposure heads 166 are arranged in a matrix of m rows and n columns. Hereinafter, when the individual exposure heads arranged in the m-th row and the n-th column are distinguished from each other, they are referred to as exposure heads 166 _mn, and when there is no need to distinguish them, they are collectively referred to as the exposure heads 166. In the present embodiment, an example is shown in which eight exposure heads 166 _{11 to} 166 ₂₄ each having a cylindrical casing are arranged in two rows and four columns.

As shown in FIG. 2, the exposure area 168 that is an area exposed by the exposure head 166 has a rectangular shape with a short side along the sub-scanning direction, and is inclined at a predetermined inclination angle θ with respect to the sub-scanning direction. ing. The exposure area 168 is tilted by tilting a mirror device 50 described later. As the stage 152 moves, the exposure area 168 also moves, and a strip-shaped exposed area 170 is formed on the photosensitive material 150 for each exposure head 166. As shown in FIGS. 1 and 2, the sub-scanning direction is opposite to the stage moving direction. In the following description, when the exposure areas by the individual exposure heads arranged in the m-th row and the n-th column are distinguished from each other, they are represented as an exposure area 168 _mn, and when there is no need to distinguish, the exposure area 168 is denoted. Collectively.

Further, as shown in FIGS. 3A and 3B, the exposure heads of the respective rows arranged in a line so that each of the strip-shaped exposed areas 170 partially overlaps the adjacent exposed areas 170. Each of 166 is arranged at a predetermined interval in the arrangement direction. The arrangement of the exposure head, can not be exposed part located between the first line of the exposure area _{168 11} and the exposure area _{168 12} is exposed by the second row of the exposure area _{168 21.}

(Schematic configuration of exposure head)
Next, the configuration of each exposure head will be described.

  FIG. 4 is a perspective view showing a schematic configuration of the exposure head. A plurality of members constituting the exposure head 166 are housed in the casing of the exposure head 166. As shown in FIG. 4, the exposure head 166 includes a micromirror represented by DMD (registered trademark) as a spatial light modulation element that modulates an incident light beam for each pixel unit according to image data. A reflective spatial light modulator (hereinafter referred to as “mirror device”) 50 is provided. As the spatial light modulator, a transmissive spatial light modulator such as a liquid crystal shutter can be used. However, it is easy to generate (modulate) a plurality of light beams corresponding to each of the plurality of pixel portions. A reflective spatial light modulation element provided with a micromirror as a pixel portion is suitable.

  The mirror device 50 is connected to a controller (not shown) that includes a data processing unit and a mirror drive control unit. The data processing unit of this controller generates a control signal for driving and controlling each micromirror in the area to be controlled by the mirror device 50 for each exposure head 166 based on the input image data. The mirror drive control unit drives and controls the angle of the reflection surface of each micromirror of the mirror device 50 for each exposure head 166 based on the control signal generated by the image data processing unit.

  Here, the configuration and operation of the mirror device 50 will be briefly described with reference to FIGS. 5 and 6. As shown in FIG. 5, the mirror device 50 includes a large number (for example, 1024 × 768) of micromirrors 62 each constituting a pixel portion (pixel) on an SRAM cell (memory cell) 60 formed on a substrate. This is a mirror device arranged in a lattice pattern. In each pixel, a micromirror 62 supported by a support column is provided at the top, and a material having high reflectance such as aluminum is deposited on the surface of the micromirror 62.

  When a digital signal is written in the SRAM cell 60, the micromirror 62 is tilted within a range of ± α degrees (for example, ± 12 degrees) with respect to the substrate side. 6A shows a state where the micromirror 62 is tilted to + α degrees when the micromirror 62 is in the on state, and FIG. 6B shows a state where the micromirror 62 is tilted to −α degrees when the micromirror 62 is in the off state. Therefore, by controlling on / off the inclination of the micro mirror 62 in each pixel of the mirror device 50 according to the image signal as shown in FIG. 5, the laser light B incident on the mirror device 50 is reflected on each micro mirror 62. Reflected in the tilt direction. A light absorber (not shown) is disposed in the direction in which the laser beam B reflected by the micromirror 62 in the off state travels.

  Hereinafter, description will be made with reference back to FIG. On the light incident side of the mirror device 50, a fiber array light source 66, a lens system 67 that corrects laser light emitted from the fiber array light source 66 and focuses it on the DMD, and laser light that has passed through the lens system 67 are mirror devices. Mirrors 69 that reflect toward 50 are arranged in this order. The fiber array light source 66 includes a laser emitting portion 68 in which emission ends (light emitting points) of optical fibers are arranged in a line along a direction corresponding to the long side direction of the exposure area 168. The laser light emitted from the lens system 67 is reflected by the mirror 69 and applied to the mirror device 50.

  On the other hand, on the light reflection side of the mirror device 50, an imaging optical system 51 that images the laser light reflected by the mirror device 50 on the photosensitive material 150 is disposed. The imaging optical system 51 irradiates the exposure area 168 on the photosensitive material 150 with laser light spatially modulated by the mirror device 50. Then, when the photosensitive material 150 moves relative to the exposure head 166, a strip-shaped exposed area 170 is formed on the photosensitive material 150.

(Optical system for multi-focus exposure)
FIG. 7 is a cross-sectional view along the optical axis for explaining the configuration of the exposure head in detail. The configuration illustrated in FIG. 4 is schematic, and the exposure head 166 of the present embodiment has a complex configuration of the imaging optical system 51 on the downstream side of the mirror device 50 in order to perform multifocal exposure. ing. Here, the multifocal exposure means that the substantially same position of the photosensitive material 150 is exposed by overlapping with a plurality of light beams having the same focal length and different focal positions. The focal position is a position near the surface of the photosensitive material 150 where the light beam for exposing the photosensitive material 150 is focused. A specific method of multifocal exposure will be described later. At this time, the range of “near the surface” of the photosensitive material, that is, the allowable range of positional deviation will be described.

  As shown in FIG. 7, a fiber array light source 66 and a condensing lens system 67 are arranged on the light incident side of the mirror device 50. The mirror device 50 is held at a predetermined position on the holding substrate 92. Laser light emitted from the lens system 67 is applied to the mirror device 50. The mirror device 50 becomes high temperature by light irradiation. For this reason, a heat sink 52 for heat dissipation is attached to the back side of the holding substrate 92.

  On the light reflection side of the mirror device 50, as the imaging optical system 51 shown in FIG. 4, a pair of lenses 72 and 74, a microlens array 78 in which a number of microlenses 76 are two-dimensionally arranged, and the thicknesses are different. Each of the parallel plate 10 and the pair of lenses 80 and 82 having a plurality of portions is arranged in this order from the mirror device 50 side. The parallel plates 10 are fixedly arranged so that parallel planes facing each other are orthogonal to the optical axis. Here, the arrangement in which the parallel plane of the parallel plate 10 is orthogonal to the optical axis will be described. However, as will be described later, as long as a plurality of light beams having the same focal length and different focal positions can be obtained, the parallel plate 10 is parallel. The parallel plate 10 can also be disposed at a predetermined angle so that the plane intersects the optical axis.

  In the present embodiment, the pair of lenses 72 and 74 and the microlens array 78 constitute a condensing optical system that condenses the laser light reflected by the mirror device 50. The optical system including the pair of lenses 72 and 74 functions as a beam expander that enlarges an image formed by the mirror device 50 and forms an image on the microlens array 78.

  The microlens array 78 corresponds to each pixel portion of the mirror device 50, and is formed by two-dimensionally arranging a large number of microlenses 76 that collect the light from each pixel portion. Each microlens 76 is disposed in the vicinity of the imaging position of the micromirror 62 by the optical system including the lenses 72 and 74 at a position where the laser beam from the corresponding micromirror 62 is incident. As will be described later, when the mirror device 50 is inclined with respect to the stage moving direction, the microlens array 78 is similarly inclined.

  In the present embodiment, the condensing optical system may be configured by omitting the microlens array 78. Or you may arrange | position the aperture array in which many apertures (opening) corresponding to each micro lens 76 was formed in the light emission side of the micro lens array 78. FIG.

  In the present embodiment, the parallel plate 10 and the pair of lenses 80 and 82 constitute an image forming optical system that forms an image of each of the laser beams condensed by the condensing optical system. The optical path length is a distance Δ that travels in a vacuum while light travels through a substance having a refractive index n by a distance d, and is represented by Δ = nd. Therefore, the parallel plate 10 having a plurality of portions having different thicknesses changes the optical path length according to the portion through which the laser beam passes, thereby maintaining the focal position of the laser beam that passes through while maintaining the focal length constant. Change. Here, “maintaining the focal length constant” does not mean that the distance from the lens center of the lens 82 to the focal point is constant, but the convergence angles of a plurality of light beams imaged by the imaging optical system are constant. It means that.

  FIG. 8 is a perspective view schematically showing the shape of a parallel plate. The parallel plate 10 is a plate-like member whose thickness changes stepwise in the stage moving direction, and has a plurality of portions with different thicknesses. Here, an example in which one side of the parallel flat plate 10 having a substantially rectangular shape in plan view is arranged in parallel to the stage moving direction is illustrated, but the mirror device 50 is arranged to be inclined with respect to the stage moving direction as will be described later. In this case, the parallel flat plate 10 is similarly inclined.

In this embodiment, the parallel plate 10, as shown in FIG. 8, the thickness d elongated flat portion 10 1 of _1, the thickness d flat portion 10 ₂ of the elongated ₂ and the thickness d ₃ flat portion 10 ₃ of the elongated is a plate-shaped member formed integrally. Greater thickness value of d ₂ is greater than the value of the thickness d _1, the value of the thickness d ₃ is the thickness d ₂ values. Flat portion 10 _1, the flat portion 10 ₂ and the flat plate portion 10 ₃ is disposed in this order toward the moving direction of the stage, it is formed to be stepwise thicker toward the moving direction of the stage.

In this example, the flat plate portion 10 ₁ , the flat plate portion 10 _2, and the flat plate portion 10 ₃ are arranged such that one parallel surface is flush with each other, so that the light incident surface of the parallel plate 10 is a flat surface. Further, the flat plate portion 10 _1, the flat portion 10 ₂ and the flat plate portions 10 _3, by the other parallel surfaces are arranged stepwise, the light emitting surface of the parallel plate 10 is uneven surface. The light incident surface of the parallel plate 10 may be a flat surface and the light exit surface may be an uneven surface, and both the light incident surface and the light exit surface of the parallel plate 10 may be an uneven surface.

As shown in FIG. 7, the laser light passing through the thickness d ₂ parallel plate 10 ₂ is the position reference focal position 56 the focused. In this case, the laser light is focused in front of the reference focal position 56, the flat plate portion 10 of the thickness d ₂ is thicker than the thickness d ₃ which passes through the flat plate portion 10 ₁ having a thickness d ₂ than the thinner d _{1 The} laser beam passing through ₃ is focused at the tip of the reference focal position 56.

FIGS. 9A to 9C are schematic diagrams for explaining the reason why the depth of focus is expanded by multifocus exposure. Here, the photosensitive material 150 is a photoresist film formed on the semiconductor substrate 151. The “focal position” is represented by a distance L _n along the optical axis from the light exit surface 82A of the lens 82 to the focal position. n is 1, 2 or 3, the flat plate portion 10 _1, and corresponds to each of the flat plate portion 10 ₂ and the flat plate portion 10 _3. The distance when the focal point is focused before the reference focal position 56 is L ₁ , the distance when the focal point is focused at the reference focal position 56 is L ₂ , and the distance when the focal point is focused before the reference focal position 56 is L ₃ . . The value of the distance L ₂ is greater by δ than the value of the distance L _1, the value of the distance L ₃ is δ only greater than the value of the distance L _2.

As shown in FIG. 9 (B), in the case where the surface of the photosensitive material 150 is in the reference focal point position 56 (when the deviation amount Z = 0), the laser beam is light-sensitive material 150 of the distance L ₂ to the focus position Focus on the surface. As shown in FIG. 9A, when the surface of the photosensitive material 150 is in front of the reference focal position 56 (in the case of the shift amount Z = −δ), the laser having a distance L ₁ to the focal position. The light is focused on the surface of the photosensitive material 150. Further, as shown in FIG. 9C, when the surface of the photosensitive material 150 is ahead of the reference focal position 56 (in the case of the shift amount Z = + δ), the laser beam having a distance L ₃ to the focal position. Is focused on the surface of the photosensitive material 150.

  The optical power density is high at the focal position, and the optical power density decreases as the distance from the focal position increases. Therefore, if the exposure amount is set so that the photosensitive material is exposed and patterned at the optical power density at the focal position, the pattern is formed only by the laser beam focused on the surface of the photosensitive material 150, and the focal point is adjusted. The pattern is not formed by the laser light that is not tied.

Therefore, even if the surface of the photosensitive material 150 is displaced in the optical axis direction from the reference focal position 56 by overlapping and exposing the substantially same position of the photosensitive material 150 with a plurality of laser beams having different focal positions, either The laser beam is focused on the surface of the photosensitive material 150, and the effective depth of focus is expanded. As described above, for example, the distance L _{1 to} the focus position, the distance L _{2 to} the focus position, and the distance L ₃ to the focus position are approximately the same position of the photosensitive material 150 with three types of laser beams having different focus positions. , The positional deviation of the photosensitive material 150 in the optical axis direction is allowed within the range of the deviation amount Z = −δ to + δ. In the present embodiment, for example, a case where the deviation amount Z is about ± 100 μm is assumed to be an allowable range.

  If the number of exposures of multiple exposure is large, the integrated amount of exposure with unfocused laser light may exceed the photosensitive threshold for patterning when the photosensitive material is exposed to light, and resolution may deteriorate. Occurs. In such a case, at the point to be exposed, the integrated amount of exposure with the laser beam not focused does not exceed the photosensitive threshold, and the integrated exposure with the focused laser beam and the unfocused laser beam. The exposure amount is set so that the amount exceeds the photosensitive threshold. Thereby, a result similar to the above is obtained.

  Further, since the focal position of the laser beam passing through the parallel plate 10 is changed by changing the optical path length of the laser beam, the focal length of the laser beam having a different focal position (in other words, the convergence angle of the laser beam) is approximately. The same. For this reason, compared with the case where multifocal exposure is performed using lenses having different focal lengths, the range in which the positional deviation in the optical axis direction is allowed is widened. Further, the beam waist diameter (spot diameter) when focusing on the surface of the photosensitive material 150 becomes substantially constant, and high-definition multifocal exposure is possible. That is, a high resolution can be maintained and a deep depth of focus can be obtained, and the exposure quality can be maintained.

  As a material of the parallel plate 10, a material transparent to the exposure light can be appropriately selected according to the wavelength of the exposure light. In addition to inorganic materials such as glass, organic materials such as resins used for optical applications can also be used as the material for the parallel plate 10. When a circuit pattern is baked on a photoresist formed on a semiconductor substrate, the photoresist is usually irradiated with blue light or ultraviolet light. When the exposure light is blue light or ultraviolet light, it is preferable to use quartz glass having excellent light resistance as the material of the parallel plate 10.

For example, assuming that the material of the parallel plate 10 is synthetic quartz (refractive index n = 1.47), when the optical magnification of the pair of lenses 80 and 82 arranged at the rear stage of the parallel plate 10 is 1, the amount of deviation In order to allow Z = | 100 μm |, the parallel plate 10 may be provided with a step of 213 μm (= 100 μm / (1.47-1)). In the example shown in FIG. 8, the thickness _{d 2} of the flat portion 10 _2, and greater than the thickness _{d 1} of the plate portion 10 ₁ only 213Myuemu, the thickness _{d 3} of the planar part 10 _3, the thickness of the flat portion 10 ₂ The thickness is made 213 μm thicker than the thickness d ₂ .

(Multifocal exposure method)
FIG. 10 is a schematic diagram showing an exposure area that is a two-dimensional image obtained by one mirror device and a block area in the exposure area. Here, the mirror device 50 is assumed to be composed of K block regions each having L rows × M columns of micromirrors 62. In this example, the number of matrices is reduced for the sake of simplification, and L = 6, M = 6, K = 36, and three block areas are indicated as A, B, and C. Each of the block regions A, B, and C corresponds to each of the flat plate portion 10 ₁ , the flat plate portion 10 _2, and the flat plate portion 10 ₃ . For this reason, the exposure area 168 on the photosensitive material 150 is irradiated with three types of laser beams having different focal positions.

As shown in FIG. 10, the mirror device 50 is tilted so that the exposure area 168 is inclined at an inclination angle θ of θ = ± tan ⁻¹ (k / L) with respect to the sub-scanning direction. Here, k is a natural number that is relatively prime to L or a number equal to L. By tilting the exposure area 168 in this way, the pitch of the scanning trajectory (scanning line) of the exposure beam by each micromirror 62 becomes narrower than the pitch of the scanning line when the exposure area 168 is not tilted, thereby improving the resolution. be able to.

  In addition, as shown in FIG. 10, the laser beam reflected (and condensed and imaged) by the plurality of micromirrors 62 scans on the same scanning line indicated by the arrow. For example, focusing on the scanning line L1, a total of three reflected light images (exposure beams 12A, 12B, and 12C) indicated by black circles are scanned on the scanning line L1. That is, as the exposure head 166 moves relative to the photosensitive material 150 (sub-scan), the same position on the photosensitive material 150 is subjected to multiple exposure with laser beams (exposure beams 12A, 12B, and 12C) having different focal positions. ing.

  For example, if the elapsed time is t seconds and the exposure timing is 1 time / a second, the reflected light image in the exposure area 168 at t = 0 is the exposure beams 12A (t = 0), 12B (t = 0), 12C ( t = 0). The reflected light images at t = a (after a second) are the exposure beams 12A (t = a), 12B (t = a), and 12C (t = a). The reflected light images at t = −a (a seconds before) are the exposure beams 12A (t = −a), 12B (t = −a), and 12C (t = −a). At t = a, the same position is subjected to multiple exposure by exposure beams 12C (t = a), 12B (t = 0), and 12A (t = -a), and exposure beams 12B (t = a) and 12C (t = a). 0) and multiple exposure of the same position.

(Exposure method according to the characteristics of the photosensitive material)
In the above example, even if the surface of the photosensitive material 150 is displaced from the reference focal position 56 in the optical axis direction, any laser beam is focused on the surface of the photosensitive material 150 and the effective depth of focus is expanded. As described above, a thick photosensitive material can be exposed by multiple exposure using laser beams having different focal positions.

  The photosensitive material 150 (photoresist film) itself may have a considerable thickness. For example, in a semi-additive method for package use, a photoresist film having a thickness of 25 μm is formed. For MEMS applications, a photoresist film having a thickness of 100 μm is formed. Multifocal exposure is an effective means for uniformly exposing such a thick photoresist film.

  Further, it is possible to perform multiple exposure with laser beams having different focal positions according to the photosensitive characteristics of the photosensitive material 150. FIGS. 11A to 11C are schematic diagrams illustrating the temporal change of multiple exposure using laser beams having different focal positions. The elapsed time is t seconds, the exposure timing is 1 time / a second, FIG. 11A shows t = 0, FIG. 11B shows t = a, and FIG. 11C shows t = 2a. Is the case. As the exposure head 166 moves relative to the photosensitive material 150 (sub-scanning), the photosensitive material 150 moves relative to the arrow direction, and the same position on the photosensitive material 150 has a laser beam (exposure) with a different focal position. Multiple exposure is performed by the beams 12A, 12B, and 12C).

In this embodiment, the photosensitive material 150 is a photoresist film formed on the substrate 151, laser light (exposure beam 12C) of the distance L ₃ to the focus position, the laser beam of the distance L ₂ to the focal position ( exposure beam 12B), and the laser beam of the distance _{L 1} to the focal position (exposure beam 12A) is irradiated in this order. Distance L ₃ > distance L ₂ > distance L ₁ .

  As shown in FIGS. 11A to 11C, the photosensitive material 150 is sequentially exposed with focused laser light from the back side close to the substrate 151, that is, from the back surface 150R side to the front surface 150S side. Will be. In the photosensitive material 150 whose light transmittance decreases after reaction with laser light, exposure can be performed without being affected by the decrease in transmittance by sequentially exposing from the back surface 150R side to the front surface 150S side.

<Second Embodiment>
Since the exposure apparatus according to the second embodiment has the same configuration as that of the first embodiment except that the direction in which the parallel plates are arranged is reversed with respect to the stage moving direction shown by the arrow, the same as in the first embodiment. A description of the components is omitted. FIG. 12 is a cross-sectional view along the optical axis for explaining in detail the configuration of the exposure head according to the second embodiment. Since the configuration is the same as that of the first embodiment except that the direction in which the parallel plates are arranged is reversed, the same components are denoted by the same reference numerals and description thereof is omitted. However, the parallel plates arranged in the opposite direction are distinguished from the parallel plates 10 of the first embodiment as parallel plates 10A.

Parallel plate 10A, like the parallel plate 10 of the first embodiment, the thickness d elongated flat portion 10 1 of _1, elongated flat portion 10 ₂ and the thickness of the thickness d ₂ d elongated flat portion 10 ₃ of ₃ is a plate-like member formed integrally. Greater thickness value of d ₂ is greater than the value of the thickness d _1, the value of the thickness d ₃ is the thickness d ₂ values. Flat portion 10 _1, the flat portion 10 ₂ and the flat plate portion 10 _3, the stage moving direction, are disposed in this order toward the opposite direction, are formed to be stepwise thinner toward the moving direction of the stage .

  FIGS. 13A to 13C are schematic views showing the temporal change of multiple exposure using laser beams having different focal positions. The elapsed time is t seconds, FIG. 13A shows the case where t = 0, FIG. 13B shows the case where t = a, and FIG. 13C shows the case where t = 2a. As the exposure head 166 moves relative to the photosensitive material 150 (sub-scanning), the photosensitive material 150 moves relative to the arrow direction, and the same position on the photosensitive material 150 has a laser beam (exposure) with a different focal position. Multiple exposure is performed by the beams 12A, 12B, and 12C).

In this embodiment, the photosensitive material 150 is a photoresist film formed on the substrate 151, laser light (exposure beam 12A) of the distance L ₁ to the focal position, the laser beam of the distance L ₂ to the focal position ( exposure beam 12B), and the laser beam of the distance _{L 3} to the focal position (exposure beam 12C) is irradiated in this order. Distance L ₃ > distance L ₂ > distance L ₁ .

  As shown in FIGS. 13A to 13C, the photosensitive material 150 is sequentially exposed with focused laser light from the back side close to the substrate 151, that is, from the front surface 150S side to the back surface 150R side. Will be. In the photosensitive material 150 in which the light transmittance is improved after the reaction with the laser light, the light can be efficiently exposed by using the effect of improving the transmittance by sequentially exposing from the front surface 150S side to the back surface 150R side. .

<Other embodiments>
(Modification of parallel plate shape and arrangement)
As described above, in the above exposure head and exposure apparatus, the plurality of portions of the parallel plate are arranged in such a manner that the photosensitive material is exposed in order from the back side when the light-sensitive material has a characteristic that the light transmittance is reduced by exposure. In addition, it may be formed in different thicknesses in stages in a predetermined direction. Further, the plurality of portions of the parallel plate have different thicknesses in stages in a predetermined direction so that the light-sensitive material has a characteristic that light transmittance increases by exposure, and is arranged in order from the surface side. It may be formed at the same time.

  In this way, by setting a plurality of focal positions in the sub-scanning direction according to the characteristics of the photosensitive material, it is possible to perform multifocal exposure by applying a suitable amount of light to the photosensitive material. That is, when the photosensitive material has a characteristic that the light transmittance is reduced by exposure, the light is exposed in order from the back side, and when the photosensitive material has a characteristic that the light transmittance is increased by exposure, the light is exposed in order from the front side. .

  In the above embodiment, the example in which the optimal exposure is performed by changing the irradiation order of the laser beams having different focal positions according to the photosensitive characteristics of the photosensitive material whose transmittance largely changes before and after the exposure has been described. In the case of a photosensitive material having a photosensitive characteristic with a small change in transmittance, it may be preferable to start the exposure from the central portion in the thickness direction and provide a pre-exposure effect on the front surface 150S side and the back surface 150R side. is there. Therefore, the shape and arrangement of the parallel plates 10 having a plurality of portions having different thicknesses are not limited to those illustrated in the first embodiment and the second embodiment.

14A to 14C are cross-sectional views along the optical axis showing a modification of the shape and arrangement of the parallel plate 10. The stage moving direction is also indicated by an arrow. For example, FIG. 14 (A), the parallel plate 10B, similarly to the parallel plate 10 of the first embodiment, the thickness of the flat plate portion 10 ₁ of _{d 1,} the thickness _{d 2} of the flat portion 10 ₂ and it includes a flat plate portion 10 ₃ of the thickness d ₃ (thickness d _3> thickness d _2> thickness d _1), after becoming once thinner toward the stage moving direction, and formed to be thicker again May be.

Further, as shown in FIG. 14 (B), parallel plate 10C is similarly flat portion 10 ₁ has a flat portion 10 ₂ and the flat plate portions 10 _3, after becoming once thicker toward the moving direction of the stage Alternatively, it may be formed to be thinner again. Further, as shown in FIG. 14C, steps may be provided over more stages (five stages in the figure). In this example, the parallel flat plate 10D is similarly provided with a flat plate portion 10 ₁ , a flat plate portion 10 ₂ , a flat plate portion 10 ₃ , a flat plate portion 10 _4, and a flat plate portion 10 ₅ , stepwise toward the stage moving direction. It is formed to be thin.

(Application to stepped substrate)
FIGS. 15A and 15B are schematic views showing an application example to a stepped substrate. In the above-described embodiment, an example in which a photosensitive material having a constant thickness is exposed has been described. However, in the present invention, effective depth of focus is expanded by multifocal exposure. The exposure apparatus of the present invention is also effective when exposing a photoresist film having a step on the surface, as in the step of exposing a photoresist when performing the above. Similarly, the exposure apparatus of the present invention is also effective when exposing a photosensitive material with waviness or warpage.

  For example, as shown in FIG. 15A, even when the photosensitive material 150 formed on the semiconductor substrate 151 is a photoresist formed in a step shape, the substantially same position of the photosensitive material 150 is By overlapping and exposing with laser beams having different focal positions (in the figure, exposure beams 12A, 12B, and 12C), any laser beam is focused on the front surface, back surface, or inside of the photosensitive material 150, and the photosensitive material 150 is exposed. It becomes possible. Similarly, as shown in FIG. 15B, a photosensitive material (photoresist) 150 formed on the semiconductor substrate 151 having a step with the same thickness can be exposed with any laser beam.

(Modified example in which parallel plate is movable)
In the above-described embodiment, the example in which the parallel plates are fixedly disposed so that the parallel planes facing each other is orthogonal to the optical axis has been described, but the parallel plates are configured to be movable in the direction orthogonal to the optical axis. However, the order of exposure with laser beams having different focal positions may be changed as appropriate. For example, as shown in FIG. 16, the parallel plates are arranged so that the parallel plates 10 of the first embodiment and the parallel plates 10A of the second embodiment are aligned in a direction (arrow A direction) perpendicular to the optical axis. The structure is connected to In the case of the photosensitive material 150 whose light transmittance decreases after reaction with laser light, the parallel plate 10 is disposed on the optical path, and in the case of the photosensitive material 150 whose light transmittance increases after reaction with laser light. Can be configured to be switchable by moving the parallel plate by a driving device (not shown) so that the parallel plate 10A is arranged on the optical path.

(Parallel plate with aperture array)
Further, in the above-described embodiment, the modification example in which the aperture array in which a large number of apertures corresponding to each microlens is formed is arranged on the light emitting side of the microlens array is illustrated. However, the aperture array is a parallel plate light. You may provide in an entrance plane.

  FIG. 17 is a cross-sectional view along the optical axis showing a modification using a parallel plate to which an aperture array is added. Since the configuration is the same as that of the first embodiment except that a parallel plate with an aperture array added is used, the same components are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 17, an aperture array 14 is added to the light incident surface of the parallel plate 10. The aperture array 14 is formed by forming a large number of apertures (openings) 16 corresponding to the respective microlenses 76 of the microlens array 78 on a light shielding film such as metal formed on the light incident surface of the parallel plate 10. is there. Since the diffused light is cut by the aperture array 14, unnecessary exposure is reduced.

10 Parallel Plates 10A to D Parallel Plates 12A to C Exposure Beam 14 Aperture Array 16 Aperture (Aperture)
50 mirror device 51 imaging optical system 52 heat sink 56 reference focal position 60 SRAM cell 62 micro mirror 66 fiber array light source 67 lens system 68 laser emitting unit 69 mirror 72 lens 76 micro lens 78 micro lens array 80 lens 82 lens 82A light emitting surface 92 Holding substrate 100 Exposure apparatus 10 ₁ to 10 ₃ Flat plate portion 150 Photosensitive material 150S Front surface 150R Back surface 151 Substrate (semiconductor substrate)
152 Stage 154 Leg 156 Installation stand 158 Guide 160 Gate 162 Scanner 164 Sensor 166 Exposure head 168 Exposure area 170 Exposed area

Claims (5)

A light source for irradiating light and a plurality of pixel units arranged in a two-dimensional manner, each of the plurality of pixel units modulating light emitted from the light source according to image data, A spatial light modulator that generates a plurality of light beams corresponding to each of the pixel units, a condensing optical system that condenses each of the plurality of light beams generated by the spatial light modulator, and the condensing optics An imaging optical system that forms an image of each of a plurality of light beams collected by the system on a photosensitive material, and the spatial light modulation between the condensing optical system and the imaging optical system. A parallel plate arranged on the optical path of the plurality of light beams generated by the element so as to intersect the optical axis and having a plurality of portions having different thicknesses so as to generate a plurality of light beams having different focal positions; A plurality of exposure heads,
Moving means for relatively moving the plurality of exposure heads exposed in the main scanning direction in the sub-scanning direction intersecting the main scanning direction with respect to the photosensitive material;
By setting a plurality of focal positions in the sub-scanning direction according to the characteristics of the photosensitive material, the photosensitive material has a focal length with respect to the photosensitive material by the relative movement in the sub-scanning direction by the moving unit. Control means for controlling the spatial light modulation element and the moving means so that multiple exposure is performed with a plurality of light beams having the same and different focal positions;
An exposure apparatus comprising:   The control means controls the spatial light modulation element and the moving means so that the photosensitive material is subjected to multiple exposure in order from the back side when the photosensitive material has a characteristic that the light transmittance is reduced by exposure. The exposure apparatus according to claim 1.   The control means controls the spatial light modulation element and the moving means so that the photosensitive material is sequentially exposed from the surface side when the photosensitive material has a characteristic that light transmittance increases by exposure. The exposure apparatus according to claim 1.   The control means controls the spatial light modulation element and the moving means so that the photosensitive material is subjected to multiple exposure in order from the back side when the photosensitive material has a characteristic that the light transmittance is reduced by exposure. In addition, when the photosensitive material has a characteristic that the light transmittance is increased by exposure, the spatial light modulator and the moving unit are controlled so that the photosensitive material is exposed in order from the surface side. The exposure apparatus according to claim 1 to be switched. The plurality of portions of the parallel plate are formed with different thicknesses so as to have different focal positions in the sub-scanning direction , and are formed with a constant thickness so that the focal positions are constant in the main scanning direction. The exposure apparatus according to any one of claims 1 to 4.

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