JP2004062155A - Exposure head and exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control a beam spot exposing the objective surface for exposure into a desired spot diameter without producing stray light or decreasing efficiency of light. <P>SOLUTION: The exposure head 166 has a micro field lens array 72 disposed on the imaging plane of the micromirror of a DMD (digital micromirror device) 50 by a lens system 54, 58. Microlenses 74 are two-dimensionally arranged in the lens array 72 to correspond to the respective micromirrors in the DMD 50. A micro imaging lens array 76 is disposed at the backward focal position of the first microlens 74, and microlenses 78 are two-dimensionally arranged in the lens array 76 to correspond to the respective microlenses 74 in the microlens array 72. The exposure head 166 projects the real image of the micromirror in a minute size imaged by the second microlens 78 as the beam spot onto the objective surface 56 for exposure through the lens system 80, 82 to expose the surface 56. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exposure head for exposing an exposure surface of a photosensitive material or the like with a laser beam spatially modulated by a spatial light modulation element according to image data, and an exposure apparatus provided with the exposure head.
[0002]
[Prior art]
Conventionally, various exposure apparatuses that perform image exposure with a light beam modulated in accordance with image data using a spatial light modulation element such as a digital micromirror device (DMD) have been proposed.
[0003]
For example, as the DMD, a mirror device in which a number of micromirrors whose reflection surfaces change in response to a control signal are two-dimensionally arranged on a semiconductor substrate such as silicon is used, and exposure using the DMD is performed. As shown in FIG. 18, the apparatus is reflected by a light source 1 that emits a laser beam, a lens system 2 that collimates the laser beam emitted from the light source 1, and DMDs 3 and DMD 3 that are arranged at substantially focal positions of the lens system 2. The lens systems 4 and 6 form an image of the laser beam on the exposure surface 5. The DMD 3 is a reflective spatial light modulator, but in FIG. 18, for the sake of simplicity, the laser beam is shown as being emitted from the DMD 3 to the exposure surface 5 side without being deflected. ing.
[0004]
In this exposure apparatus, each of the micromirrors of the DMD 3 is on / off controlled by a control device (not shown) by a control signal generated according to image data or the like to modulate (deflect) the laser beam, and the exposure surface is modulated by the modulated laser beam. 2 exposures. Here, the lens systems 4 and 6 are configured as a magnifying optical system, and the exposure area on the exposure surface 5 is enlarged with respect to the surface portion of the DMD 3 on which the micromirrors are arranged.
[0005]
In the exposure apparatus as described above, the micromirror in DMD and the exposure surface 56 are usually conjugated with each other, and the reflected light image by the micromirror is formed on the exposure surface 5 by the lens systems 4 and 6, and this reflection is performed. The exposure surface 5 is exposed using the optical image as a beam spot.
[0006]
However, when the area of the exposure area with respect to the exposure surface 5 is enlarged with respect to the area of the surface portion of the DMD 3 by the lens systems 4 and 6, the area (spot diameter) of the beam spot on the exposure surface 5 is also enlarged according to the enlargement ratio. Therefore, the MTF (Modulation Transfer Function) characteristic on the exposure surface 5 is lowered according to the enlargement ratio of the exposure area.
[0007]
Therefore, in the exposure apparatus as described above, as shown in FIG. 19, a plurality of microlenses 7 are arranged between the lens system 6 and the exposure surface 5 so as to correspond to each micromirror of the DMD 3 on a one-to-one basis. In some cases, the spot diameter on the exposure surface 5 is adjusted (reduced) to a desired size by reducing the laser beam reflected by the micromirror by these microlenses 7.
[0008]
[Problems to be solved by the invention]
However, in the exposure apparatus as described above, the laser emission part in the light source 1 usually has a certain area and cannot be regarded as a point light source. For this reason, as shown in FIG. 19, the laser beam reflected by the micromirror of DMD 3 also has a certain spread angle αs corresponding to the area of the laser emitting portion. As a result, in the exposure apparatus as described above, when a microlens is used to reduce the spot diameter of the beam spot on the exposure surface 5, a part of the laser beam reflected by the predetermined micromirror is stray light SL. The light enters the microlens 7 other than the microlens 7 corresponding to the predetermined micromirror. In many cases, such stray light SL forms a ghost image GI on the exposure surface 5 through the microlens 7, and generates an exposure portion that becomes a noise component on the exposure surface 5.
[0009]
Further, in the exposure apparatus as described above, an aperture having an aperture diameter corresponding to the spot diameter of a required beam spot is disposed between the lens system 6 and the exposure surface 5 without using the microlens 7, and this aperture. It is conceivable to reduce the beam diameter on the exposure surface 5 by using this aperture. However, when such an aperture is used, the light loss due to the aperture increases as the reduction ratio with respect to the laser beam increases, and the light utilization efficiency is remarkably increased. descend.
[0010]
In view of the above facts, an object of the present invention is to provide an exposure head and an exposure apparatus that can adjust a beam spot for exposing an exposure surface to a desired spot diameter without generating stray light and reducing light efficiency. There is.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, an exposure head according to a first aspect of the present invention is an exposure head for two-dimensionally exposing an exposure surface with a plurality of laser beams, wherein the laser beam is emitted from a laser emitting portion. The illuminating means that emits and a plurality of pixel portions whose light modulation states change according to the control signal are two-dimensionally arranged, and the laser beam incident from the laser emitting portion is exposed and non-exposed by the pixel portion. A spatial light modulation element that modulates any one of the above, a first optical system that forms an image of each pixel portion in the spatial light modulation element, and an image position of each of the plurality of pixel portions. A plurality of first microlenses that condense the laser beams that are two-dimensionally arranged at the same pitch as the image size and that are modulated by the plurality of pixel portions into the exposure state;
A plurality of second microlenses that are arranged at rear focal positions of the plurality of first microlenses, and that respectively form a real image of the pixel portion on the exposure surface, and are imaged by the second microlenses. The exposure surface is exposed using a real image of the pixel portion as a beam spot.
[0012]
In the exposure head according to the first aspect, the plurality of first microlenses condense the laser beams modulated in the exposure state by the plurality of pixel portions in the spatial light modulator, and The plurality of second microlenses arranged at the back focal position respectively form a real image of the pixel portion on the exposure surface, thereby condensing the laser beam modulated in the exposure state by the first microlens. Since the focused laser beam can be incident on the second microlens, even if the laser beam modulated in the exposure state has a spread angle corresponding to the area of the laser emitting portion, it is modulated in the exposure state by a predetermined pixel portion. It is possible to prevent a part of the laser beam from entering the second microlens other than the second microlens corresponding to the predetermined pixel portion as stray light.
[0013]
In the exposure head according to claim 1, since the focal length of the second microlens is appropriately set, the size of the real image of the pixel portion formed as a beam spot on the exposure surface can be reduced to an arbitrary size. Even when the area of the exposure area is enlarged with respect to the size of the spatial light modulator using the magnifying optical system as the first optical system, it is possible to prevent the MTF characteristic from being lowered on the exposure surface.
[0014]
Here, the first microlens and the second microlens do not need to be configured by a single lens, but may be configured by combining a plurality of lenses in order to improve chromatic aberration, spherical aberration, and the like. In addition, the spatial light modulator does not necessarily need to completely block the laser beam from the microlens when the laser beam is modulated to the non-exposure state, and causes the laser beam whose intensity is weakened to enter the microlens. Anyway.
[0015]
An exposure head according to a second aspect of the present invention is the exposure head according to the first aspect, wherein a real image group that is a set of images of the pixel portion formed by the plurality of second microlenses is formed on the exposure surface. And a second optical system that forms an image.
[0016]
An exposure head according to a third aspect of the present invention is the exposure head according to the second aspect, wherein a spot of a beam spot on the exposure surface is formed at a real image position where the pixel portion is imaged by the plurality of second microlenses. A plurality of apertures each having an opening diameter and an opening shape corresponding to the diameter and the spot shape are arranged.
[0017]
According to the above-described exposure head, the real image position where the pixel portion is imaged by the second microlens has an aperture diameter and an aperture shape corresponding to the spot diameter and spot shape of the beam spot on the exposure surface. By arranging the aperture, the aperture can block the light that becomes a noise component such as scattered light and diffracted light from the laser beam emitted from the second microlens, so that the beam spot projected on the exposure surface has the required spot shape. Can be shaped with high accuracy, and light that is a noise component can be prevented from being projected outside the beam spot.
[0018]
An exposure apparatus according to a third aspect of the present invention is the exposure head according to the first, second, or third aspect, and the arrangement direction of the plurality of pixel portions of the exposure head is inclined with respect to the scanning direction with respect to the exposure surface. And moving means for relatively moving the exposure head in the scanning direction during exposure with respect to the exposure surface.
[0019]
According to the above-described exposure apparatus, j pixel portions are arranged in the spatial light modulator along a direction (row direction) substantially orthogonal to the scanning direction, and a direction (column direction) substantially corresponding to the scanning direction. ) Are arranged in the spatial light modulation element, the exposure head is supported while supporting the exposure head so that the arrangement direction of the pixel parts of the spatial light modulation element is inclined with respect to the scanning direction. Relative movement in the scanning direction makes it possible to set different positions on the same scanning line on the exposure surface by an integral multiple of j, that is, (j × N) laser beams in accordance with the inclination angle of the pixel portion in the arrangement direction with respect to the scanning direction. Since exposure becomes possible, the pixel density of the exposure pattern formed on the exposure surface can be increased to the required density by appropriately adjusting the tilt angle in the arrangement direction of the pixel portions, and substantially the same position on the same scanning line. (Dot) Since exposure can be performed k / N times (multiple exposure) with a laser beam modulated by k / N pixel units arranged in the same column of the spatial light modulator, the resolution of the exposure pattern formed on the exposure surface is also improved. it can.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Configuration of exposure apparatus]
As shown in FIG. 1, the exposure apparatus 142 according to the embodiment of the present invention includes a flat plate stage 152 that holds a sheet-like photosensitive material 150 by adsorbing to the surface. Two guides 158 extending along the stage moving direction are installed on the upper surface of the thick plate-shaped installation base 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. The exposure device 142 is provided with a drive device (not shown) for driving the stage 152 along the guide 158.
[0021]
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 end portions of the gate 160 is fixed to both side surfaces of the installation table 156. A scanner 162 is provided on one side of the gate 160, and a plurality of (for example, two) detection sensors 164 for detecting the front and rear ends of the photosensitive material 150 are provided on the other side. The scanner 162 and the detection sensor 164 are respectively attached to the gate 160 and fixedly arranged above the moving path of the stage 152. The scanner 162 and the detection sensor 164 are connected to a controller (not shown) that controls them.
[0022]
As shown in FIGS. 2 and 3B, the scanner 162 includes a plurality of (for example, 14) exposure heads 166 arranged in an approximately matrix of m rows and n columns (for example, 3 rows and 5 columns). ing. In this example, four exposure heads 166 are arranged in the third row in relation to the width of the photosensitive material 150. In addition, when showing each exposure head arranged in the m-th row and the n-th column, it is expressed as an exposure head 166 mn.
[0023]
An exposure area 168 by the exposure head 166 has a rectangular shape with a short side in the scanning direction. Therefore, as the stage 152 moves, a strip-shaped exposed area 170 is formed for each exposure head 166 in the photosensitive material 150. In addition, when showing the exposure area by each exposure head arranged in the nth column of the m-th row, it is expressed as an exposure area 168mn.
[0024]
Also, as shown in FIGS. 3A and 3B, each of the exposure heads in each row arranged in a line so that the strip-shaped exposed regions 170 are arranged in the direction orthogonal to the scanning direction without gaps. The arrangement direction is shifted by a predetermined interval (a natural number multiple of the long side of the exposure area, twice in the present embodiment). Therefore, can not be exposed area between the first row of the exposure area _{168 11} and the exposure area _{168 12,} it can be exposed by the second row of the exposure area 16821 and exposure area _{168 31} in the third row.
[0025]
As shown in FIGS. 4 and 5A, each of the exposure heads 16611 to 166mn is a digital micromirror device as a spatial light modulation element that modulates an incident light beam for each pixel in accordance with image data. (DMD) 50 is provided. The DMD 50 is connected to a controller (not shown) including 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 region to be controlled by the DMD 50 for each exposure head 166 based on the input image data. The area to be controlled will be described later. The mirror drive control unit controls the angle of the reflection surface of each micromirror in the DMD 50 for each exposure head 166 based on the control signal generated by the image data processing unit. The control of the angle of the reflecting surface will be described later.
[0026]
As shown in FIG. 4, the exposure head 166 is provided with an illumination unit 144 on the light incident side of the DMD 50. The illumination unit 144 includes a fiber array light source 66 having a laser emission portion 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, a fiber array A lens system 67 that corrects laser light emitted from the light source 66 and collects the light on the DMD, and a mirror 69 that reflects the laser light transmitted through the lens system 67 toward the DMD 50 are arranged in this order.
[0027]
As shown in FIG. 6, the DMD 50 is configured such that a micromirror 62 is supported by a support column on an SRAM cell (memory cell) 60, and a large number of (pixels) (pixels) are formed. For example, the mirror device is configured by arranging 600 × 800 micromirrors in a lattice pattern. Each pixel is provided with a micromirror 62 supported by a support column at the top, and a material having a high reflectance such as aluminum is deposited on the surface of the micromirror 62. The reflectance of the micromirror 62 is 90% or more. A silicon gate CMOS SRAM cell 60 manufactured on a normal semiconductor memory manufacturing line is disposed directly below the micromirror 62 via a support including a hinge and a yoke, and is entirely monolithic (integrated type). ).
[0028]
When a digital signal is written in the SRAM cell 60 of the DMD 50, the micromirror 62 supported by the support is inclined within a range of ± α degrees (for example, ± 10 degrees) with respect to the substrate side on which the DMD 50 is disposed with the diagonal line as the center. It is done. FIG. 7A shows a state in which the micromirror 62 is tilted to + α degrees in the on state, and FIG. 7B shows a state in which the micromirror 62 is tilted to −α degrees in the off state. Therefore, by controlling the inclination of the micromirror 62 in each pixel of the DMD 50 as shown in FIG. 6 according to the image signal, the light incident on the DMD 50 is reflected in the inclination direction of each micromirror 62. .
[0029]
FIG. 6 shows an example of a state in which a part of the DMD 50 is enlarged and the micromirror 62 is controlled to + α degrees or −α degrees. On / off control of each micromirror 62 is performed by a controller (not shown) connected to the DMD 50. Here, the light reflected by the on-state micromirror 62 is modulated into an exposure state, and enters an imaging optical system 146 (see FIG. 5) provided on the light exit side of the DMD 50. The light reflected by the micromirror 62 in the off state is modulated to the non-exposure state and enters a light absorber (not shown).
[0030]
Further, it is preferable that the DMD 50 is disposed slightly inclined so that the short side direction forms a predetermined angle θ (for example, 0.1 ° to 0.5 °) with the scanning direction. 8A shows the scanning trajectory of the reflected light image (exposure beam) 53 by each micromirror when the DMD 50 is not tilted, and FIG. 8B shows the scanning trajectory of the exposure beam 53 when the DMD 50 is tilted. Show.
[0031]
In the DMD 50, a number of micromirror arrays in which a large number (for example, 800) of micromirrors are arranged along the longitudinal direction (row direction) are arranged in a short direction (for example, 600 sets). as shown in FIG. 8 (B), by inclining the DMD 50, the pitch _{P 1} of the scanning locus of the exposure beams 53 from each micromirror (scanning line), than the pitch _{P 2} of the scanning lines in the case of not inclined DMD 50 It becomes narrower and the resolution can be greatly improved. On the other hand, the inclination angle of the DMD 50 is small, the scanning width _{W 2} in the case of tilting the DMD 50, which is substantially equal to the scanning width _{W 1} when not inclined DMD 50.
[0032]
Further, substantially the same position (dot) on the same scanning line is overlapped and exposed (multiple exposure) by different micromirror rows. In this way, by performing multiple exposure, it is possible to control a minute amount of the exposure position and to realize high-definition exposure. Further, the joints between the plurality of exposure heads arranged in the scanning direction can be connected without any step by controlling a very small amount of exposure position.
[0033]
Note that the same effect can be obtained by arranging the micromirror rows in a staggered manner by shifting the micromirror rows by a predetermined interval in a direction orthogonal to the scanning direction instead of inclining the DMD 50.
[0034]
For example, as shown in FIG. 9A, the fiber array light source 66 includes a plurality of (for example, six) laser modules 64, and one end of the multimode optical fiber 30 is coupled to each laser module 64. Has been. The other end of the multimode optical fiber 30 is coupled with an optical fiber 31 having the same core diameter as the multimode optical fiber 30 and a cladding diameter smaller than the multimode optical fiber 30, as shown in FIG. A laser emission portion 68 is configured by arranging emission ends (light emission points) of the optical fiber 31 in a line along a direction orthogonal to the scanning direction. As shown in FIG. 9D, the light emitting points can be arranged in two rows along a direction orthogonal to the scanning direction. Such an arrangement of the emission end portions of the optical fiber 31 is determined based on the spot shape of the beam spot projected onto the exposure surface 56, as will be described later.
[0035]
As shown in FIG. 9B, the emission end of the optical fiber 31 is sandwiched and fixed between two support plates 65 having a flat surface. Further, a transparent protective plate 63 such as glass is disposed on the light emitting side of the optical fiber 31 in order to protect the end face of the optical fiber 31. The protection plate 63 may be disposed in close contact with the end surface of the optical fiber 31 or may be disposed so that the end surface of the optical fiber 31 is sealed. The exit end of the optical fiber 31 is easily deteriorated because it has a high light density and easily collects dust. However, by providing the protective plate 63, it is possible to prevent the dust from adhering to the end face and to delay the deterioration. .
[0036]
In the example of FIG. 9B, in order to arrange the emission ends of the optical fibers 31 with a small cladding diameter in a line without any gap, a multi-mode optical fiber 30 adjacent to each other with a large cladding diameter is arranged between The optical fibers 31 are stacked, and the output ends of the optical fibers 31 coupled to the stacked multimode optical fibers 30 are coupled to the two adjacent multimode optical fibers 30 at the portion where the cladding diameter is large. Are arranged so as to be sandwiched between the emission ends of the two.
[0037]
For example, as shown in FIG. 10, an optical fiber 31 having a length of 1 to 30 cm and having a small cladding diameter is coaxially connected to the tip of the multimode optical fiber 30 having a large cladding diameter on the laser light emission side. Can be obtained by linking them together. The two optical fibers 30 and 31 are fused and joined so that the incident end face of the optical fiber 31 is coincident with the outgoing end face of the multimode optical fiber 30 so that the central axes of both optical fibers coincide. As described above, the diameter of the core 31 a of the optical fiber 31 is the same as the diameter of the core 30 a of the multimode optical fiber 30.
[0038]
In addition, a short optical fiber in which an optical fiber having a short cladding diameter and a large cladding diameter is fused to an optical fiber having a short cladding diameter and a large cladding diameter may be coupled to the output end of the multimode optical fiber 30 via a ferrule or an optical connector. Good. By detachably coupling using a connector or the like, the tip portion can be easily replaced when an optical fiber having a small cladding diameter is broken, and the cost required for exposure head maintenance can be reduced. Hereinafter, the optical fiber 31 may be referred to as an emission end portion of the multimode optical fiber 30.
[0039]
The multimode optical fiber 30 and the optical fiber 31 may be any of a step index type optical fiber, a graded index type optical fiber, and a composite type optical fiber. For example, a step index type optical fiber manufactured by Mitsubishi Cable Industries, Ltd. can be used. In the present embodiment, the multimode optical fiber 30 and the optical fiber 31 are step index type optical fibers, and the multimode optical fiber 30 has a cladding diameter = 125 μm, a core diameter = 25 μm, NA = 0.2, an incident end face. The transmittance of the coat is 99.5% or more, and the optical fiber 31 has a cladding diameter = 60 μm, a core diameter = 25 μm, and NA = 0.2.
[0040]
In general, in laser light in the infrared region, propagation loss increases as the cladding diameter of the optical fiber is reduced. For this reason, a suitable cladding diameter is determined according to the wavelength band of the laser beam. However, the shorter the wavelength, the smaller the propagation loss. In the case of laser light having a wavelength of 405 nm emitted from a GaN-based semiconductor laser, the cladding thickness {(cladding diameter−core diameter) / 2} is set to infrared light in the wavelength band of 800 nm. The propagation loss hardly increases even if it is about ½ of the case of propagating infrared light and about ¼ of the case of propagating infrared light in the 1.5 μm wavelength band for communication. Therefore, the cladding diameter can be reduced to 60 μm.
[0041]
However, the cladding diameter of the optical fiber 31 is not limited to 60 μm. The clad diameter of an optical fiber used in a conventional fiber light source is 125 μm, but the depth of focus becomes deeper as the clad diameter becomes smaller. Therefore, the clad diameter of a multimode optical fiber is preferably 80 μm or less, more preferably 60 μm or less. Preferably, it is 40 μm or less. On the other hand, since the core diameter needs to be at least 3 to 4 μm, the cladding diameter of the optical fiber 31 is preferably 10 μm or more.
[0042]
The laser module 64 is configured by a combined laser light source (fiber light source) shown in FIG. This combined laser light source includes a plurality of (for example, seven) chip-like lateral multimode or single mode GaN-based semiconductor lasers LD1, LD2, LD3, LD4, LD5, LD6, arrayed and fixed on the heat block 10. And LD7, collimator lenses 11, 12, 13, 14, 15, 16, and 17 provided corresponding to each of the GaN-based semiconductor lasers LD1 to LD7, one condenser lens 20, and one multi-lens. Mode optical fiber 30. The number of semiconductor lasers is not limited to seven.
[0043]
The GaN-based semiconductor lasers LD1 to LD7 all have the same oscillation wavelength (for example, 405 nm), and the maximum output is also all the same (for example, 100 mW for the multimode laser and 30 mW for the single mode laser). As the GaN-based semiconductor lasers LD1 to LD7, lasers having an oscillation wavelength other than the above 405 nm in a wavelength range of 350 nm to 450 nm may be used.
[0044]
As shown in FIGS. 12 and 13, the above-described combined laser light source is housed in a box-shaped package 40 having an upper opening together with other optical elements. The package 40 includes a package lid 41 created so as to close the opening thereof. After the degassing process, a sealing gas is introduced, and the package 40 and the package lid 41 are closed by closing the opening of the package 40 with the package lid 41. 41. The combined laser light source is hermetically sealed in a sealed space formed by 41.
[0045]
A base plate 42 is fixed to the bottom surface of the package 40, and the heat block 10, a condensing lens holder 45 that holds the condensing lens 20, and the multimode optical fiber 30 are disposed on the top surface of the base plate 42. A fiber holder 46 that holds the incident end is attached. The exit end of the multimode optical fiber 30 is drawn out of the package from an opening formed in the wall surface of the package 40.
[0046]
Further, a collimator lens holder 44 is attached to the side surface of the heat block 10, and the collimator lenses 11 to 17 are held. An opening is formed in the lateral wall surface of the package 40, and wiring 47 for supplying a driving current to the GaN-based semiconductor lasers LD1 to LD7 is drawn out of the package through the opening.
[0047]
In FIG. 13, in order to avoid complication of the drawing, only the GaN semiconductor laser LD7 among the plurality of GaN semiconductor lasers is numbered, and only the collimator lens 17 among the plurality of collimator lenses is numbered. doing.
[0048]
FIG. 14 is a front view of the collimator lenses 11 to 17 and their mounting portions. Each of the collimator lenses 11 to 17 is formed in a shape obtained by cutting a region including the optical axis of a circular lens having an aspherical surface into a long and narrow plane. This elongated collimator lens can be formed, for example, by molding resin or optical glass. The collimator lenses 11 to 17 are closely arranged in the arrangement direction of the light emitting points so that the length direction is orthogonal to the arrangement direction of the light emitting points of the GaN-based semiconductor lasers LD1 to LD7 (left and right direction in FIG. 14).
[0049]
On the other hand, each of the GaN-based semiconductor lasers LD1 to LD7 includes an active layer having a light emission width of 2 μm, and each of the laser beams B1 in a state parallel to the active layer and a divergence angle in a direction perpendicular to the active layer, respectively, for example A laser emitting ~ B7 is used. These GaN-based semiconductor lasers LD1 to LD7 are arranged so that the light emitting points are arranged in a line in a direction parallel to the active layer.
[0050]
Accordingly, in the laser beams B1 to B7 emitted from the respective light emitting points, the direction in which the divergence angle is large coincides with the length direction and the divergence angle is small with respect to the elongated collimator lenses 11 to 17 as described above. Incident light is incident in a state where the direction coincides with the width direction (direction perpendicular to the length direction). That is, the collimator lenses 11 to 17 have a width of 1.1 mm and a length of 4.6 mm, and the horizontal and vertical beam diameters of the laser beams B1 to B7 incident thereon are 0.9 mm and 2. 6 mm. Each of the collimator lenses 11 to 17 has a focal length f = 3 mm, NA = 0.6, and a lens arrangement pitch = 1.25 mm.
[0051]
The condensing lens 20 is formed by cutting a region including the optical axis of a circular lens having an aspheric surface into a long and narrow shape in parallel planes, and is long in the arrangement direction of the collimator lenses 11 to 17, that is, in a horizontal direction and short in a direction perpendicular thereto. Is formed. The condenser lens 20 has a focal length f2 = 23 mm and NA = 0.2. This condensing lens 20 is also formed by molding resin or optical glass, for example.
[0052]
Next, the imaging optical system 146 provided on the light reflection side of the DMD 50 in the exposure head 166 will be described. As shown in FIG. 5A, the exposure head 166 is provided with an imaging optical system 146 for projecting a light source image on the exposure surface 56 on the light reflection side of the DMD 50. In the imaging optical system 146, a pair of lens systems 54, 58, a micro field lens array 72, a micro imaging lens array 76, and a pair of lens systems 80, 82 are arranged in this order from the DMD 50 side to the exposure surface 56. Has been.
[0053]
Here, the lens systems 54 and 58 are configured as a magnifying optical system. By expanding the cross-sectional area of the light beam reflected by the micromirror 62 of the DMD 50, the lens system 54 and 58 is formed by the light beam reflected by the DMD 50 on the exposure surface 56. The area of the exposure area 168 is expanded to a required size. The micro field lens array 72 is formed by integrally forming a plurality of first micro lenses 74 corresponding to each micro mirror 62 of the DMD 50 that reflects light from the illumination unit 144 in a one-to-one manner. The lens 74 is disposed on the imaging surface of the micromirror 62 on the optical axis of the laser beam that has passed through the lens systems 54 and 58, and the diameter thereof is substantially the same as the image size of the real image of the micromirror 62. ing. In the micro field lens array 76, the first micro lenses 74 are two-dimensionally arranged at the same pitch as the image size of the micro mirror 62 at the image position.
[0054]
The micro imaging lens array 76 is provided with a plurality of apertures (aperture stops) 78 corresponding to the plurality of first microlenses 74 in the microfield lens array 72 in a one-to-one manner. Two microlenses 79 are arranged. The lens diameter of the second microlens 79 coincides with the aperture diameter of the aperture 78, and the optical axis of the second microlens 79 and the optical axis of the first microlens 74 coincide.
[0055]
In the imaging optical system 146, the focal length of the lens system 54 is f1, and the focal length of the lens system 58 is f2. The focal length of the second microlens 79 is f4. The micro imaging lens array 72 is disposed at the rear focal position of the first microlens 74. The lens systems 80 and 82 are configured as, for example, equal-magnification optical systems, and a real image group, which is a set of real images of the micromirrors 62 formed by the plurality of second microlenses 79, is exposed on the exposure surface 56. To form an image. Here, the focal lengths of the lens system 80 and the lens system 82 are set to f5. The lens systems 54 and 58 and the lens systems 80 and 82 in the imaging optical system 146 are shown as one lens in FIG. 5, but a plurality of lenses (for example, a convex lens and a concave lens) are used. It may be a combination.
[0056]
In the imaging optical system 146, the spot diameter and the spot shape of the beam spot imaged on the exposure surface 56 depend on the resolution of the exposure pattern formed in the exposed region 170, the scanning speed of the exposure head 166, and the scanning direction of the DMD 50. It is determined according to design items such as the size of the tilt angle and the characteristics of the photosensitive material 150. On the other hand, the aperture diameter and the aperture shape of the aperture 78 are set according to the spot diameter and spot shape of the beam spot imaged on the exposure surface 56.
[0057]
With reference to FIG. 5, the operation of the first microlens 74 and the second microlens 79 in the imaging optical system 146 will be described. The lens systems 54 and 58 constituting the magnifying optical system enlarge the area of the exposure area 168 on the exposure surface 56 to a required size by enlarging the cross-sectional area of the light beam reflected by the DMD 50. At this time, the laser beam reflected by the micromirror 62 of the DMD 50 is also transmitted through the lens systems 54 and 58, so that the beam diameter is expanded according to the magnification of the lens systems 54 and 58. Therefore, when the microlenses 74 and 79 are not arranged in the imaging optical system 146, the spot diameter of each beam spot BS projected on the exposure surface 56 is set to the exposure area 168 as shown in FIG. It will be bigger depending on the size. For this reason, even when scanning exposure is performed as shown in FIG. 8A, the MTF (Modulation Transfer Function) characteristics of the exposure area 168 are lowered in accordance with the magnification ratio of the lens systems 54 and 58.
[0058]
In order to prevent the deterioration of the MTF characteristics as described above and to prevent a part of the laser beam modulated into the exposure state by the micromirror 62 from becoming stray light, the imaging optical system 146 includes a lens system 54, A plurality of first microlenses 74 are two-dimensionally arranged so as to correspond to the respective micromirrors 62 of the DMD 50 on the image forming surface on which a real image of the micromirror 62 is formed by the 58. A plurality of second microlenses 79 are two-dimensionally arranged at the back focal position of one microlens 74.
[0059]
Here, as shown in FIG. 15, the second microlens 79 reduces the real image RI _{1 of the} micromirror 62 and places the real image RI ₂ on the imaging surface 85, which is a virtual surface equivalent to the exposure surface 56. Form. As a result, as shown in FIG. 5C, even when the exposure area 168 is enlarged by the lens systems 54 and 58 at a high magnification, the spot diameter of the beam spot BS can be reduced to a required size, and the exposure surface can be reduced. The deterioration of the MTF characteristic at 56 can be prevented. The first microlens 74 acts as a field lens for condensing the laser beam, and condenses one laser beam having a spread angle αs corresponding to the area along the direction perpendicular to the optical axis of the laser emitting unit 68. The light is incident on one second microlens 79.
[0060]
Next, a method for setting the focal length f3 of the first microlens 74 will be specifically described. As shown in FIG. 15, the opening diameter 2R of the first micro-lens 74 is consistent with the size of the real image RI ₁ micromirrors 62 formed by the lens system 58. Further, the aperture diameter of the second microlens 79 disposed at the rear focal position of the first microlens 74 is set to (2R / n). At this time, n is a reduction ratio of the opening diameter of the second microlens 79 with respect to the opening diameter of the first microlens 74, and this n (n ≧ 1) is determined based on the spot diameter of the beam spot BS.
[0061]
Consider a condition in which all the light beams transmitted through the first microlens 74 are theoretically incident on the second microlens 79, that is, the aperture 78. At this time, if the spread angle of the light flux from the first microlens 74 toward the light source is αs, the spread angle αs can be obtained by the following equation (1).
[0062]
αs = (R / n) / f3 (1)
From the equation (1), the focal length f3 of the micro lens 74 is obtained by the following equation (2).
[0063]
f3 = (R / n) / αs (2)
When the focal length f3 of the first microlens 74 is set to a value calculated by the above equation (2), the light (laser beam) transmitted through the first microlens 74 is theoretically as shown in FIG. The entire amount is incident on one second microlens 79 without being blocked by the aperture 78. However, the light transmitted through the first microlens 74 includes light that becomes noise components such as diffracted light due to aberration of the first microlens 74 and scattered light due to scattering, and the light that becomes such noise components is apertured. In actuality, a slight light loss is caused by the aperture 78. However, the focal length f3 obtained by the equation (2) is a theoretical optimum value for minimizing the light loss. For this reason, the exposure head 166 considers the shape of the beam spot BS by the aperture 78, the noise light removability, and the like, so that the aperture 78 and the second microlens 79 are positioned around a minute distance from the back focal position of the first microlens 74. It is allowed to be placed in
[0064]
FIG. 16 shows a case where the reduction ratio n is particularly 1, and the opening diameter of the second microlens 79 is equal to the opening diameter 2R of the first microlens 74.
[0065]
Here, the imaging surface 85 is conjugated with the exposure surface 56 via the lens systems 80 and 82. As a result, a real image of the micro mirror 62 having the same size as the real image RI ₂ of the micro mirror 62 reduced by the second micro lens 79 is formed on the exposure surface 56. The exposure device 142 exposes the exposure surface 56 using the real image of the micromirror 62 formed by the lens systems 80 and 82 as a beam spot BS.
[Operation of exposure apparatus]
Next, the operation of the exposure apparatus 142 will be described.
[0066]
In each exposure head 166 of the scanner 162, laser beams B1, B2, B3, B4, B5, B6 emitted in a divergent light state from each of the GaN-based semiconductor lasers LD1 to LD7 constituting the combined laser light source of the fiber array light source 66. , And B7 are collimated by collimator lenses 11-17 as shown in FIG. The collimated laser beams B <b> 1 to B <b> 7 are collected by the condenser lens 20 and converge on the incident end face of the core 30 a of the multimode optical fiber 30.
[0067]
In the present embodiment, a condensing optical system is configured by the collimator lenses 11 to 17 and the condensing lens 20, and a combining optical system is configured by the condensing optical system and the multimode optical fiber 30. That is, the laser beams B1 to B7 condensed as described above by the condenser lens 20 enter the core 30a of the multimode optical fiber 30 and propagate through the optical fiber to be combined with one laser beam B. The light is emitted from the optical fiber 31 coupled to the output end of the multimode optical fiber 30.
[0068]
In each laser module 64, when the coupling efficiency of the laser beams B1 to B7 to the multimode optical fiber 30 is 0.85 and each output of the GaN-based semiconductor lasers LD1 to LD7 is 30 mW, as shown in FIG. A combined laser beam B having an output of 180 mW (= 30 mW × 0.85 × 7) can be obtained for each of the optical fibers 31 arranged in an array. Therefore, the output from the laser emitting unit 68 in which the six optical fibers 31 are arranged in an array is about 1 W (= 180 mW × 6).
[0069]
For example, in a conventional fiber light source in which a semiconductor laser and an optical fiber are coupled on a one-to-one basis, a laser having an output of about 30 mW (milliwatt) is usually used as the semiconductor laser, and the core diameter is 50 μm and the cladding diameter is 125 μm. Since a multimode optical fiber having a numerical aperture (NA) of 0.2 is used, if an output of about 1 W (watt) is to be obtained, 48 multimode optical fibers (8 × 6) must be bundled. In other words, since the area of the light emitting region is 0.62 mm ² (0.675 mm × 0.925 mm), the luminance at the laser emitting portion 68 is 1.6 × 10 6 (W / m ² ), which is per optical fiber. The luminance is 3.2 × 10 6 (W / m ² ).
[0070]
On the other hand, in this embodiment, as described above, an output of about 1 W can be obtained with six multimode optical fibers, and the area of the light emitting region at the laser emitting portion 68 is 0.0081 mm ² (0.325 mm). × 0.025 mm), the brightness at the laser emitting portion 68 is 123 × 10 6 (W / m ² ), and the brightness can be increased by about 80 times compared to the conventional case. Further, the luminance per optical fiber is 90 × 10 6 (W / m ² ), and the luminance can be increased by about 28 times compared with the conventional one. As a result, the angle of the light beam incident on the DMD 50 is reduced, and as a result, the angle of the light beam incident on the exposure surface 56 is also reduced, so that the focal depth of the beam spot can be increased.
[0071]
Image data corresponding to the exposure pattern is input to a controller (not shown) connected to the DMD 50 and temporarily stored in a frame memory in the controller. This image data is data representing the density of each pixel constituting the image by binary values (whether or not dots are recorded).
[0072]
The stage 152 that has adsorbed the photosensitive material 150 to the surface is moved at a constant speed from the upstream side to the downstream side of the gate 160 along the guide 158 by a driving device (not shown). When the leading edge of the photosensitive material 150 is detected by the detection sensor 164 attached to the gate 160 when the stage 152 passes under the gate 160, the image data stored in the frame memory is sequentially read out for a plurality of lines. A control signal is generated for each exposure head 166 based on the image data read by the data processing unit. Then, each of the micromirrors of the DMD 50 is controlled on and off for each exposure head 166 based on the generated control signal by the mirror drive control unit.
[0073]
When the DMD 50 is irradiated with laser light from the fiber array light source 66, the laser light reflected when the micromirror of the DMD 50 is on is imaged on the exposure surface 56 of the photosensitive material 150 by the lens systems 54 and 58. The In this manner, the laser light emitted from the fiber array light source 66 is turned on and off for each pixel, and the photosensitive material 150 is exposed in pixel units (exposure area 168) that is approximately the same number as the number of pixels used in the DMD 50. Further, the photosensitive material 150 is moved at a constant speed together with the stage 152, so that the photosensitive material 150 is scanned in the direction opposite to the stage moving direction by the scanner 162, and a strip-shaped exposed region 170 is formed for each exposure head 166. Is done.
[0074]
When the scanning of the photosensitive material 150 by the scanner 162 is completed and the rear end of the photosensitive material 150 is detected by the detection sensor 164, the stage 152 is moved to the most upstream side of the gate 160 along the guide 158 by a driving device (not shown). It returns to a certain origin, and again moves along the guide 158 from the upstream side to the downstream side of the gate 160 at a constant speed.
[0075]
In the exposure apparatus 142 described above, the plurality of first microlenses 74 condense the laser beams modulated in the exposure state by the respective micromirrors 62 in the DMD 50 and at the rear focal positions of these first microlenses 74. The plurality of arranged second microlenses 79 each form a real image of the micromirror on the exposure surface, thereby condensing the laser beam modulated in the exposure state by the first microlens 74, Therefore, even when the laser beam modulated in the exposure state has a divergence angle corresponding to the area of the laser emitting portion 68, it is modulated into the exposure state by the predetermined micromirror 62. The second microlens 79 or the like in which a part of the laser beam that has been formed corresponds to a predetermined micromirror 62. It can be prevented from entering the stray light to the second micro lens 79.
[0076]
Further, the exposure apparatus 142 appropriately sets the focal length of the second microlens 79 according to the spot diameter of the required beam spot BS, so that the real image of the micromirror 62 formed as the beam spot BS on the exposure surface 56 is obtained. Since the size can be reduced to an arbitrary size, even when the area of the exposure area 168 is enlarged by the lens systems 54 and 58, a decrease in the MTF characteristic on the exposure surface 56 can be prevented.
[0077]
In the exposure apparatus 142 of the present embodiment, the first microlens 74 and the second microlens 79 are each constituted by a single lens. However, one or both of the first microlens 74 and the second microlens 79 are used. Each may be configured by combining a plurality of lenses (microlenses). Thus, by combining the micro lenses 74 and 79 with a plurality of lenses (micro lenses), chromatic aberration, spherical aberration, and the like can be effectively improved.
[0078]
In addition, as shown in FIG. 17, an aperture array 86 provided with apertures 88 corresponding to the spot diameter and spot shape of the beam spot BS on the exposure surface 56 is disposed near the rear focal position of the second microlens. May be. Thus, by arranging the aperture 88 having an aperture diameter and an aperture shape corresponding to the spot diameter and spot shape of the beam spot BS on the exposure surface 56 in the vicinity of the rear focal position of the second microlens 79, the second microlens is arranged. Since light that becomes noise components such as scattered light and diffracted light in the laser beam emitted from 79 can be blocked by the aperture 88, the beam spot BS projected on the exposure surface 56 can be accurately shaped into a required spot shape, and It is possible to prevent light that is a noise component from being projected outside the beam spot BS.
[0079]
If the clearance from the exposure head 166 to the exposure surface 56 is sufficiently short, the lens systems 80 and 82 (second optical system) are omitted from the imaging optical system 146 as shown in FIG. The real image of each micromirror 62 of the DMD 50 imaged by the second microlens 78 of the image lens array 86 may be directly projected onto the exposure surface 56 as a beam spot BS to expose the photosensitive material 150.
[0080]
In the exposure apparatus 142 according to the present embodiment, a DMD is used as a spatial modulation element. For example, a MEMS (Micro Electro Mechanical Systems) type spatial modulation element (SLM; Spatial Light Modulator), or transmission by an electro-optic effect is used. Even when a spatial modulation element other than the MEMS type such as an optical element (PLZT element) for modulating light or a liquid crystal optical shutter (FLC) is used in place of the DMD 50, the imaging optical system 146 is shown in FIG. 5 or FIG. If one is used, it is possible to prevent the lowering of the MTF characteristics in the exposure area 168 while suppressing the light amount loss due to the aperture 78.
[0081]
Note that MEMS is a general term for micro systems that integrate micro-sized sensors, actuators, and control circuits based on micro-machining technology based on the IC manufacturing process. It means a spatial modulation element that is driven by the electromechanical operation used.
[0082]
【The invention's effect】
As described above, according to the exposure head and the exposure apparatus of the present invention, the beam spot for exposing the exposure surface can be adjusted to a desired spot diameter without generating stray light and reducing light efficiency.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an external appearance of an exposure apparatus according to a first embodiment.
FIG. 2 is a perspective view showing a configuration of a scanner of the exposure apparatus according to the first embodiment.
FIG. 3A is a plan view showing an exposed area formed on a photosensitive material, and FIG. 3B is a view showing an arrangement of exposure areas by each exposure head.
FIG. 4 is a perspective view showing a schematic configuration of an exposure head of the exposure apparatus according to the embodiment of the present invention.
5A is a side view showing a configuration of an imaging optical system in the exposure head shown in FIG. 4, and FIGS. 5B and 5C are plan views of an exposure area by the exposure head.
FIG. 6 is a partially enlarged view showing a configuration of a digital micromirror device (DMD).
7A and 7B are explanatory diagrams for explaining the operation of the DMD. FIG.
FIGS. 8A and 8B are plan views showing the arrangement of exposure beams and scanning lines in a case where the DMD is not inclined and in a case where the DMD is inclined. FIG.
9A is a perspective view showing the configuration of a fiber array light source, FIG. 9B is a partially enlarged view of A, and FIGS. 9C and 9D show the arrangement of light emitting points in a laser emitting section. FIG.
FIG. 10 is a diagram showing a configuration of a multimode optical fiber.
FIG. 11 is a plan view showing a configuration of a combined laser light source.
FIG. 12 is a plan view showing the configuration of a laser module.
13 is a side view showing the configuration of the laser module shown in FIG. 12. FIG.
14 is a partial side view showing the configuration of the laser module shown in FIG. 12. FIG.
15 is a side view of the first micro lens and the second micro lens in the exposure head shown in FIG. 5, and shows a configuration example in which the aperture diameter of the second micro lens is smaller than that of the first micro lens.
16 is a side view of the first microlens and the second microlens in the exposure head shown in FIG. 5, and shows a configuration example in which the aperture diameters of the first microlens and the second microlens are made equal. FIG.
17 is a side view showing the configuration of the exposure head when an aperture is added to the rear focal position of the second microlens shown in FIG. 5. FIG.
FIG. 18 is a side view along the optical axis showing the configuration of a conventional exposure head.
FIG. 19 is a side view showing a configuration in which a microlens is applied to a conventional exposure head.
20 is a side view showing the configuration when the second lens system is omitted from the imaging optical system shown in FIG. 5. FIG.
[Explanation of symbols]
50 DMD (Spatial Light Modulator)
54, 58 Lens system (first optical system)
56 Exposure surface 62 Micromirror (pixel part)
68 Laser emitting unit 72 Micro lens array 74 First micro lens 76 Aperture array 78 Aperture 79 Second micro lens 80, 82 Lens system (second optical system)
86 Aperture array 88 Aperture 142 Exposure device 144 Illumination unit (illumination means)
146 Imaging optical system 166 Exposure head

Claims (4)

An exposure head for two-dimensionally exposing an exposure surface with a plurality of laser beams,
An illumination means for emitting a laser beam from the laser emitting section;
A plurality of pixel portions whose light modulation states change according to the control signal are two-dimensionally arranged, and the laser beam incident from the laser emitting portion is modulated by the pixel portion into either an exposure state or a non-exposure state. A spatial light modulator;
A first optical system that forms an image of each pixel portion in the spatial light modulator, and two-dimensionally arranged at the image positions of the plurality of pixel portions at the same pitch as the image size formed at the image positions. A plurality of first microlenses for condensing the laser beam modulated into the exposure state by the plurality of pixel units;
A plurality of second microlenses that are arranged at rear focal positions of the plurality of first microlenses, and that respectively form a real image of the pixel portion on the exposure surface;
An exposure head that exposes the exposure surface using a real image of the pixel portion formed by the second microlens as a beam spot. 2. The exposure according to claim 1, further comprising: a second optical system that forms on the exposure surface a real image group that is a set of real images of the pixel unit that is imaged by the plurality of second microlenses. head. A plurality of apertures each having an aperture diameter and an aperture shape corresponding to the spot diameter and spot shape of the beam spot on the exposure surface are arranged at real image positions where the pixel portions are imaged by the plurality of second microlenses. The exposure head according to claim 1, wherein: An exposure head according to claim 1, 2 or 3,
Moving means for supporting the exposure head so that an arrangement direction of the plurality of pixel portions is inclined with respect to a scanning direction with respect to the exposure surface, and moving the exposure head in the scanning direction at the time of exposure with respect to the exposure surface; ,
An exposure apparatus comprising:

Images