WO2018088550A1 - Direct imaging exposure device and direct imaging exposure method - Google Patents

Abstract

[Problem] To enable resolution to be effectively increased beyond a conventional resolution limit such that the pattern of applied light approaches a designed exposure pattern as much as possible. [Solution] Light in an exposure pattern is applied to an exposure area E by an exposure unit provided with a spatial light modulator that is a DMD, and while an object W is being moved through the exposure area E by a moving mechanism, a photosensitive layer at the surface of the object W is exposed by applying light having a critical exposure amount or more thereto. A point to be exposed of the object W is located at corresponding coordinates G corresponding to a pixel mirror in an on state of the spatial light modulator at multiple times and multiply exposed. The number of times of multiple exposure at an exposure point the distance of which to the boundary of a designed exposure pattern is less than an exposure point pitch is smaller than a maximum number of times set according to the distance to the boundary.

Description

Direct imaging exposure apparatus and direct imaging exposure method

The invention of this application relates to a direct imaging exposure technique.

An exposure technique for exposing an object having a photosensitive layer formed on the surface to expose the photosensitive layer is actively used for forming various microcircuits and microstructures as a main technique of photolithography. In a typical exposure technique, light is irradiated onto a mask on which a pattern similar to the exposure pattern is formed, and an image of the mask is projected onto the surface of the object so that the light of the exposure pattern is irradiated onto the object. To do.

In addition to the exposure technique using such a mask, a technique is known in which an image is directly formed on the surface of an object using a spatial light modulator for exposure. Hereinafter, this technique is referred to as direct imaging exposure and abbreviated as DI exposure in this specification.
In the DI exposure, a typical spatial light modulator is a DMD (Digital Mirror Device). The DMD has a structure in which minute square mirrors are arranged in a rectangular lattice. Each mirror has an angle controlled with respect to the optical axis, and takes an attitude that reflects light from the light source to reach the object and an attitude that does not allow the light from the light source to reach the object. To get. The DMD includes a controller that controls each mirror, and the controller controls each mirror according to the exposure pattern so that the surface of the object is irradiated with light of the exposure pattern.

In the case of DI exposure, since a mask is not used, superiority is demonstrated in high-mix low-volume production. In the case of exposure using a mask, it is necessary to prepare a mask for each product type, which requires a large cost including the cost of storing the mask. Further, when exchanging masks for production of different varieties, it is necessary to stop the operation of the apparatus, and it takes time and effort to resume. For this reason, it becomes a factor which productivity falls. On the other hand, in the case of DI exposure, it is only necessary to prepare control data for each mirror for each product type. When manufacturing different product types, it is possible to respond only by changing the control data, which is advantageous in terms of cost and productivity. Sex is remarkable. Further, it is possible to finely adjust the exposure pattern for each work (exposure target) as necessary, and the process flexibility is excellent.

As the spatial light modulator, in addition to the DMD which is a reflection type, a transmission type is being studied. A typical transmissive spatial light modulator is an application of a transmissive liquid crystal display device, and controls the transmission and blocking of light according to the alignment of the liquid crystal in each cell, so that the light of the exposure pattern is applied to the object. It is intended to be irradiated.
In the following description, each portion of the spatial light modulator that reflects or transmits light and reaches the object is referred to as a pixel. In the case of a reflective spatial light modulator, the pixel is referred to as each mirror, and in the case of a transmissive spatial light modulator, the pixel is referred to as a cell. Further, for each pixel, a state in which light is reflected or transmitted to reach the object is referred to as an on state, and a state in which light does not reach the object is referred to as an off state.

JP 2004-355006 A

Although DI exposure has the above-mentioned advantages, it also has drawbacks unique to digital technology. One of them is the limit of exposure resolution. In DI exposure, it is not possible to perform exposure that is finer than the projection magnification of the pixel size of each pixel of the spatial light modulator. In this respect, it can also be said that exposure cannot be performed faithfully according to an exposure pattern as design information (a pattern desired to be exposed on an object in product design, hereinafter referred to as a design exposure pattern). The design exposure pattern is, for example, a design pattern of a circuit formed on a substrate when a product to be manufactured is a printed circuit board.

More specifically, in DI exposure, a raster image (bitmap image) is created according to the design exposure pattern. This is because the design exposure pattern is often a vector image, but on-off control of each pixel of the spatial light modulator cannot be performed with vector image data. In this case, the data resolution of the raster image can only be fined up to the pixel size of the spatial light modulator × projection magnification. This is because even higher data resolution is meaningless because it cannot be expressed by a spatial light modulator.

On the other hand, the design exposure pattern data is often data having a resolution higher than the resolution of the raster image. In this case, when the raster image is generated according to the design exposure pattern, the image inevitably becomes “rough”. This leads to several problems.
This point will be described with reference to FIGS. FIGS. 10 and 11 are diagrams showing problems caused by the image data for controlling the spatial light modulator becoming coarser than the design exposure pattern.

Of these, FIG. 10 shows the problem of jaggy generation. FIG. 10 (1) shows an example of the design exposure pattern, and FIG. 10 (2) shows a raster image generated from the design exposure pattern of (1). Assume that the design exposure pattern has an oblique boundary as shown in FIG. “Inclined” means oblique with respect to the arrangement direction of the pixels of the spatial light modulator. In this case, when the design exposure pattern is binarized to form a raster image, jaggy occurs at an oblique boundary as shown in FIG.
When jaggies occur, for example, when exposure is performed to form a fine circuit, there is a problem that unnecessary radiation (noise) tends to occur in the formed fine circuit. In general, if the pattern formed by exposure has jaggies, it does not look good. Therefore, it is required in DI exposure to form a pattern having a smooth contour shape with as little jaggies as possible.

In addition, there is a problem that the degree of freedom in changing an exposure pattern is low in relation to conversion to a raster image. This is schematically shown in FIG.
The design exposure pattern often includes a linear portion like the formation of a fine circuit. In this case, the line width is rounded to the unit of pixel size in the raster image. For example, if the line width of the design exposure pattern is 8.4 pixels, it cannot be 8.4 pixels, so that the line width is 8 pixels as shown in FIG. In this case, for example, when it is desired to change the line width to 7.4 pixels in the design exposure pattern, the raster image is rounded to 7 pixels. In this case, the center position of the line (the center position in the width direction) should not be changed in many cases. In this case, the line width becomes 6 pixels as shown in FIG. That is, the line is thinner by 1.4 pixels than the designed exposure pattern.

As described above, in DI exposure, when raster image data is generated from a design exposure pattern, the data is inevitably coarse, so that the exposure cannot be performed with the design exposure pattern or a resolution close thereto, which causes a problem. . In addition to the above, although details are omitted, if the line width is corrected in the exposure of the line pattern extending obliquely 45 degrees as shown in FIG. 10B, the correction unit is multiplied by √ (2). There is also a problem that overcorrection occurs.

The invention of the present application has been made to solve such a problem of DI exposure, and when performing exposure by controlling the spatial light modulator according to the design exposure pattern, the pattern of the irradiated light is designed exposure. An object of the present invention is to provide an excellent technique capable of effectively increasing the resolution beyond the limit of the conventional resolution so as to be as close as possible to the pattern.

In order to solve the above-mentioned problem, the invention according to claim 1 of this application includes an exposure unit that irradiates an exposure area with light of a pattern according to a design exposure pattern,
A moving mechanism that relatively moves through the exposure area an object having a photosensitive layer that is exposed to light when exposed to a critical exposure amount or more;
The exposure unit
The light source is disposed at a position where light from the light source is irradiated, and is either an on state where light is directed toward the exposure area or an off state where light is not directed toward the exposure area A spatial light modulator that spatially modulates the light from the light source so that the light irradiated to the exposure area having a large number of pixels has a pattern according to the design exposure pattern, and spatially by the spatial light modulator A direct imaging exposure apparatus comprising an optical system for projecting modulated light onto an exposure area,
A modulator controller for controlling each pixel of the spatial light modulator;
A storage unit that stores exposure control data that is data for on / off control of each pixel by the modulator controller;
Corresponding coordinates corresponding to each pixel of the spatial light modulator are set in the exposure area,
On the surface of the object, exposure points are set as indicating the locations to be exposed, and each exposure point is a point separated from each other by an exposure point pitch distance,
The optical system projects a pixel pattern of the pixel on each corresponding coordinate corresponding to each pixel in the on state of the spatial light modulator,
In the moving mechanism, the position of one exposure point of the target object is exposed by the pixel pattern on the scan line along the moving direction and is also superimposedly exposed by the peripheral portion of the pixel pattern on the adjacent scan line. The illuminance distribution in each pixel pattern is a distribution that is high in the central part and low in the peripheral part,
The exposure control data is positioned a predetermined number of times including the same exposure point on the surface of the target object once and twice or more at the corresponding coordinates on which the pixel pattern is projected as the target object is moved by the moving mechanism. To be exposed,
The predetermined number of times in the exposure control data is the maximum number at an exposure point where the distance to the boundary of the design exposure pattern is equal to or greater than the exposure point pitch, and the exposure where the distance to the boundary of the design exposure pattern is less than the exposure point pitch. In the point, the number of times is less than the maximum number set according to the distance to the boundary.
In order to solve the above problem, the invention according to claim 2 has a configuration in which the spatial light modulator is a digital mirror device in the configuration of claim 1.
In order to solve the above problem, the invention described in claim 3 is either an on state where light is directed toward the exposure area or an off state where light is not directed toward the exposure area. A modulator irradiating step of irradiating light from a light source onto a spatial light modulator having a large number of pixels;
A modulator control step of controlling the spatial light modulator to control the spatial light modulator so that the light irradiated to the exposure area becomes a pattern according to the design exposure pattern;
A projection step of projecting light from the spatial light modulator by an optical system;
A direct imaging exposure method comprising: a moving step of relatively moving an object having a photosensitive layer formed on the surface thereof exposed by exposure exceeding a critical exposure amount through an exposure area;
Corresponding coordinates corresponding to each pixel of the spatial light modulator are set in the exposure area,
On the surface of the object, exposure points are set as indicating the locations to be exposed, and each exposure point is a point separated from each other by an exposure point pitch distance,
The projecting step is a step of projecting a pixel pattern of the pixel on each corresponding coordinate corresponding to each pixel that is in the on state of the spatial light modulator,
In the projection step and the movement step, the position of one exposure point of the object is exposed by the pixel pattern on the scan line along the movement direction, and is also superimposed by the peripheral portion of the pixel pattern on the adjacent scan line. The step of moving the object so as to be exposed, the illuminance distribution in each pixel pattern is a distribution that is high in the central part and low in the peripheral part,
The modulator control step and the moving step are predetermined in which the same required exposure point on the surface of the object includes one time and two times or more at the corresponding coordinates on which the pixel pattern is projected as the object is moved by the moving mechanism. It is a step to be exposed at a number of times,
The predetermined number of times in the exposure control data is the maximum number of exposure points where the distance to the boundary of the design exposure pattern is greater than or equal to the exposure point pitch, and the distance to the boundary of the design exposure pattern is less than the exposure point pitch. In the exposure point, the number of times is less than the maximum number set according to the distance to the boundary.
In order to solve the above-mentioned problem, the invention according to claim 4 has a configuration in which, in the configuration of claim 3, the spatial light modulator is a digital mirror device.

As described below, according to the invention of this application, multiple exposure in which the same exposure point is exposed multiple times is adopted, and the number of exposures of each exposure point is set according to the distance to the boundary of the design exposure pattern. Therefore, the size of the effective exposure area can be adjusted more finely. For this reason, the resolution of effective exposure is improved.

It is the schematic of the direct imaging exposure apparatus of embodiment. It is the schematic of the exposure unit with which the apparatus shown in FIG. 1 is provided. It is the isometric view schematic shown about the exposure area by each exposure unit. It is the perspective view which showed roughly each pixel pattern and the illumination distribution of each pixel pattern. It is the figure which showed notionally about multiple exposure. It is the figure which showed notionally about multiple exposure. It is the figure which showed an example of the photosensitive characteristic of a photosensitive layer. It is the figure which showed typically about the exposure control data in the DI exposure apparatus of embodiment. It is the schematic which showed an example of the exposure control data in DI exposure apparatus of embodiment. It is the figure shown about the subject of DI exposure technique. It is the figure shown about the subject of DI exposure technique.

Next, modes for carrying out the invention of the present application (hereinafter referred to as embodiments) will be described.
First, an embodiment of the DI exposure apparatus will be described. FIG. 1 is a schematic diagram of a DI exposure apparatus according to an embodiment.
The DI exposure apparatus shown in FIG. 1 includes an exposure unit 1 that irradiates an exposure area with light having a pattern according to a design exposure pattern, and a moving mechanism 2 that relatively moves the object W through the exposure area.
The DI exposure apparatus of this embodiment is an apparatus for manufacturing a printed circuit board. Therefore, the object W has a conductive film for wiring formed on a substrate and a photosensitive layer formed thereon. The photosensitive layer is a coated resist film.

FIG. 2 illustrates the exposure unit 1 provided in the apparatus shown in FIG. FIG. 2 is a schematic view of the exposure unit 1 provided in the apparatus shown in FIG. As shown in FIG. 2, the exposure unit 1 projects a light source 3, a spatial light modulator 4 that spatially modulates the light from the light source 3, and an optical that projects an image of light modulated by the spatial light modulator 4. A system (hereinafter referred to as a projection optical system) 5 is provided.

The light source 3 that outputs light having an optimum wavelength according to the photosensitive wavelength of the photosensitive layer in the object W is used. The photosensitive wavelength of the resist film is often from the visible short wavelength region to the ultraviolet region, and as the light source 3, one that outputs light in the visible short wavelength region such as 405 nm or 365 nm is used. Further, in order to make use of the performance of the spatial light modulator 4, it is preferable to output coherent light. For this reason, a laser light source is preferably used. For example, a gallium nitride (GaN) based semiconductor laser is used.

In this embodiment, a DMD is used as the spatial light modulator 4. As described above, in the DMD, each pixel is a minute mirror (not shown in FIG. 2). The mirror (hereinafter referred to as a pixel mirror) is a square mirror having a square of about 13.68 μm, for example, and has a structure in which a large number of pixel mirrors are arranged in a rectangular lattice pattern. The number of arrangement is, for example, 1024 × 768.

The spatial light modulator 4 includes a modulator controller 41 that controls each pixel mirror. The DI exposure apparatus according to the embodiment includes a main control unit 7 that controls the whole. The modulator controller 41 controls each pixel mirror in accordance with a signal from the main control unit 7. Each pixel mirror has a plane on which the pixel mirrors are arranged as a reference plane, a first posture along the reference plane, and a second tilted by, for example, about 11 to 13 ° with respect to the reference plane. The posture can be taken. In this embodiment, the first posture is in an off state and the second posture is in an on state.
The spatial light modulator 4 includes a drive mechanism that drives each pixel mirror, and the modulator controller 41 independently controls whether each pixel mirror takes the first posture or the second posture. It can be done. Such a spatial light modulator 4 is available from Texas Instruments.

As shown in FIG. 2, the exposure unit 1 includes an irradiation optical system 6 that irradiates light from the light source 3 to such a spatial light modulator 4. In this embodiment, the irradiation optical system 6 includes an optical fiber 61. In order to form an image with higher illuminance, one exposure unit 1 includes a plurality of light sources 3, and an optical fiber 61 is provided for each light source 3. As the optical fiber 61, for example, a quartz-based multimode fiber is used.

In order to form an image with high accuracy using the spatial light modulator 4 which is a DMD, it is desirable that parallel light be incident and reflected on each pixel mirror 42, and obliquely with respect to each pixel mirror 42. It is desirable to make light incident. For this reason, as shown in FIG. 2, the irradiation optical system 6 is configured to make light incident obliquely on the collimator lens 62 that collimates the light emitted from each optical fiber 61 and spreads, and the spatial light modulator 4. And a reflection mirror 63. “Inclined” means to be inclined with respect to the reference plane of the spatial light modulator 4. In terms of the incident angle θ with respect to the reference surface, for example, the angle is approximately 22 to 26 °.

The projection optical system 5 includes two projection lens groups 51 and 52 and a microlens array (hereinafter abbreviated as MLA) 53 disposed between the projection lens groups 51 and 52. The MLA 53 is arranged in an auxiliary manner in order to perform exposure with higher shape accuracy. The MLA 53 is an optical component in which a large number of minute lenses are arranged in a right-angle lattice shape. Each lens element corresponds to each pixel mirror of the spatial light modulator 4 on a one-to-one basis.

In the exposure unit 1 described above, the light from the light source 3 is guided by the optical fiber 61 and then enters the spatial light modulator 4 by the irradiation optical system 6. At this time, each pixel mirror of the spatial light modulator 4 is controlled by the modulator controller 41 and is in a posture that is selectively inclined according to the design exposure pattern. That is, according to the design exposure pattern, the pixel mirror located at the position where the light should reach the exposure area is in the second posture (ON state), and the other pixel mirrors are in the first posture (OFF state). It is said. The light reflected on the off-state pixel mirror does not reach the exposure area, but only the light reflected on the on-state pixel mirror. For this reason, the exposure area is irradiated with light having a pattern according to the design exposure pattern.

On the other hand, as shown in FIG. 1, the DI exposure apparatus according to the embodiment includes a stage 21 on which an object W is placed. The moving mechanism 2 is a mechanism that linearly moves the stage 21 on which the object W is placed.
As the moving mechanism 2, for example, as shown in FIG. 1, a linear moving mechanism including a ball screw 22, a pair of linear guides 23, a servo motor 24 that rotates the ball screw 22, and the like is employed. In addition, there may be used a linear motor stage that moves the stage 21 linearly using the action of magnetism. The stage 21 supports the object W so as not to move by a method such as vacuum suction. In order to reduce the contact area with the workpiece W, a structure having a large number of protrusions on the surface may be used.
The moving direction by the moving mechanism 2 is the horizontal direction. An exposure area is set on a moving line (scan line) of the stage 21 by the moving mechanism 2.

As shown in FIG. 1, a plurality of exposure units 1 are provided. Each exposure unit 1 has the same configuration. The plurality of exposure units 1 are arranged in two rows in a direction perpendicular to the moving direction of the moving mechanism 2. One column is arranged so as to be shifted in the arrangement direction with respect to the other column. This is because the exposure area by each exposure unit 1 covers the surface of the object W without a gap. This point will be described with reference to FIG. FIG. 3 is a schematic perspective view showing an exposure area by each exposure unit.

FIG. 3 schematically shows a state in which the object W reaching the lower side of each exposure unit 1 is exposed. In FIG. 3, an exposure area E by each exposure unit 1 is indicated by a square frame on the surface of the object W. Actually, in each exposure area E, light of a pattern according to the design exposure pattern is irradiated, and exposure is performed with the pattern.
The object W is irradiated with light of a pattern formed in each exposure area E while moving in the direction (X direction) indicated by the arrow in FIG. At this time, since the two rows of exposure units 1 are arranged so as to be shifted from each other, exposure is performed without a gap even in the horizontal direction perpendicular to the moving direction.

Now, in the DI exposure apparatus of such an embodiment, a configuration is adopted in which the resolution is effectively increased beyond the limit of resolution in conventional DI exposure. This configuration is mainly realized by data for controlling the spatial light modulator 4 (hereinafter referred to as exposure control data) sent from the main control unit 7 to the modulator controller 41. Hereinafter, this point will be described.

The exposure control data is closely related to a light irradiation pattern (hereinafter referred to as a pixel pattern) by each pixel mirror 42 of the spatial light modulator 4. First, the pixel pattern and the illuminance distribution in each pixel pattern will be described. FIG. 4 is a perspective view schematically showing each pixel pattern and the illuminance distribution of each pixel pattern.
As described above, the DI exposure apparatus according to the embodiment uses a DMD as the spatial light modulator 4, and the projection optical system 5 generates a pixel pattern S by each pixel mirror 42 in the on state as shown in FIG. 4. Project. The projection position of each pixel pattern S is the position of each corresponding coordinate G set in the exposure area. A pixel pattern S is projected onto the corresponding coordinates G corresponding to the pixel mirror 42 in the on state. In the embodiment, since each pixel mirror 42 is a square, each corresponding coordinate corresponds to the position of each intersection of a right-angle lattice having an aspect ratio of 1.

The distance between corresponding coordinates in the vertical and horizontal directions depends on the exposure magnification. When the magnification is larger than 1, the inter-coordinate distance is longer than one side of the pixel mirror 42, and when the magnification is smaller than 1, the inter-coordinate distance is shorter than one side of the pixel mirror 42. In the case of exposure for producing a printed circuit board, the magnification is often larger than 1. In the embodiment, the shape of each pixel mirror 42 is a square, but the image (pixel pattern) by the projection optical system 5 is a rounded image (substantially circular image).

The object W is moved in the horizontal direction by the moving mechanism 2. During this movement, the object W passes through the irradiation spot of each pixel pattern S and is exposed. The exposure required part of the target object W is specified by XY coordinates based on a specific position on the surface of the target object W. These coordinates are hereinafter referred to as “exposure required points” and indicated by M. Each exposure point M is in the shape of a grid and is separated at a constant interval. Hereinafter, this interval is referred to as an exposure point pitch. The exposure point pitch corresponds to the pixel size in the raster image described above.
Each exposure point M passes through the center of each pixel pattern S when the object W moves by the moving mechanism 2, and exposure is performed at this time. Hereinafter, the line on which each exposure point M moves is referred to as a scan line, and is indicated by a one-dot chain line SL in FIG. In the example of FIG. 4, the scan line SL is in the X direction of the object W, but this is not essential, and there are cases where the scan line SL is in an oblique direction with respect to the XY direction.

As shown in FIG. 4, when an exposure point M moves through a scan line SL and passes through the pixel pattern S, the location of the exposure point M is a pixel pattern on the adjacent scan line SL. It is also exposed by S ′. In other words, although there is a slight time lag, it passes through the peripheral portion of the pixel pattern S 'of the adjacent scan line SL, so that the peripheral portion is also exposed. In other words, the moving mechanism 2 is configured such that each exposure point M required is exposed by the pixel pattern on the scan line SL and is also superimposedly exposed by the peripheral portion of the pixel pattern on the adjacent scan line SL. It is a mechanism for moving M. The location of each exposure point M is a region on the surface of the object W specified by the exposure point M, and is a region centered on the exposure point M. This area is a rectangular area having an exposure point pitch as one side.

FIG. 4 shows the illuminance distribution by the pixel pattern S as I, and the illuminance distribution by the pixel pattern S ′ as I ′. As shown in FIG. 4, the illuminance distributions I and I ′ in the pixel patterns S and S ′ are high in the non-overlapping portions and low in the overlapping portions. More specifically, the distribution is large at the center of one pixel pattern and gradually decreases toward the periphery. The illuminance distribution may be a so-called Gaussian distribution. Note that the illuminance distribution I is symmetrical with respect to the center (corresponding coordinates G) of the pixel pattern, and has a distribution as shown in FIG. 4 in any horizontal direction.

The DI exposure apparatus according to the embodiment optimizes the exposure control data on the assumption that the light irradiation pattern and its illuminance distribution by each pixel mirror are as described above. More specifically, a predetermined number of exposures (hereinafter referred to as “multiple exposure”) including one time and two or more times are performed on a portion of the surface of the object W that requires exposure of a predetermined amount or more (exposure required portion). In order to improve the effective resolution, the number of exposures is optimized.

5 and 6 are diagrams conceptually showing the multiple exposure. FIG. 5 (1) shows conventional exposure that is not multiple exposure. 5 (2) shows two multiple exposures with two exposures, FIG. 5 (3) shows three multiple exposures with three exposures, and FIG. 5 (4) shows four exposures. 4 multiple exposures are shown.
In FIGS. 5 (1) to (4), the left graph shows the individual exposure amounts for each continuous (overlapping) pixel pattern, and the right graph shows the entire region where the pixel patterns are continuous. The exposure amount is shown. In FIGS. 5 (2) to 5 (4), the broken line in the graph on the left indicates a state in which the exposure amount increases with each exposure.

First, for comparison, normal exposure that is not multiple exposure will be described. FIG. 5A is the same diagram as FIG. 4 and shows the exposure amount by each pixel pattern projected onto the continuous exposure required portions. Since the exposure is performed once, the exposure amount is a distribution similar to the illuminance distribution I of each pixel pattern.
The exposure amount obtained by integrating the exposure amounts shown on the left side of FIG. 5A is the actual exposure amount, which is shown on the right side. Hereinafter, this exposure amount is referred to as an area integrated exposure amount.
In this embodiment, some of the exposure points are exposed only once. Since only one exposure is included in the concept of “multiple exposure”, in the following description, only one exposure is referred to as “one multiple exposure”. The two exposures are called “double”, the three exposures are called “three multiplexes”, and the four exposures are called “four multiplexes”.

The photosensitive layer formed on the surface of the object W is exposed to a certain critical amount of exposure. FIG. 7 is a diagram showing an example of the photosensitive characteristics of the photosensitive layer. FIG. 7 shows a negative resist as an example. As shown in FIG. 7, the photosensitive layer becomes zero (insoluble) in the developer at a certain critical exposure amount E _C. Increasing the amount of exposure further does not change its characteristics. Hereinafter, such an exposure amount E _C as the critical exposure.

In FIG. 5A, the area integrated exposure amount is set to be equal to or greater than the critical exposure amount E _{C at the} corresponding coordinates irradiated with the light of the pixel pattern. This is achieved by appropriately adjusting the illuminance (average illuminance or peak illuminance) in each pixel pattern. As shown in FIG. 6, of the main exposure position, since the area integrated exposure amount at a position outside E _B than the corresponding coordinate on the edge is below the critical exposure, the position E _B is effective to be exposed This is the edge of the region (hereinafter referred to as the effective exposure boundary).

Similarly, in the case of the multiple exposure shown in FIGS. 5 (1) to (4), the area integrated exposure amount is shown on the right side. FIG. 6 is a diagram showing the area integrated exposure amount shown on each right side of FIGS. 5 (1) to 5 (4) in one graph for easy understanding.
In Figure 6, a main exposure point of main exposure position to the rightmost of the main exposure position and G _1. When the main exposure position to reach the G ₁ and 1 multiplex, when a 2 multiplexing, when the 3 multiplexing, when the 4 multiplexed are shown. The exposure point pitch is indicated by D.

As shown in FIG. 6, according to continue to increase the multiplicity 1, and so multiple → 4 multiplexing, the position of the effective exposure boundary E _B is shifted outward. In this example, when four times are multiplexed, one adjacent exposure point (G ₂ ) reaches the critical exposure amount E _C. That results in that the number of effective exposure boundary E _B is quadrupled (it is possible to select the three coordinates in between), apparently means that perform exposure at four times the resolution.
In this example, in the case of one multiplex, a position P _{1 that} is 1/4 of the exposure point pitch D with respect to the exposure point (G ₁ ) located at the end reaches the critical exposure amount E _C. Yes. Accordingly, when it is desired to set G ₁ as the effective exposure boundary, it is sufficient to use 4 multiples at the exposure point required immediately before G ₁ (indicated by G ₀ ) and set the number of exposures to 0 for the exposure point G ₁ required. become. Hereinafter, the number of exposures 0 is referred to as “0 multiple” for convenience.

Thus, the DI exposure apparatus embodiments, and more than twice the exposure to main exposure position selected, and thereby device for improving the effective exposure resolution by shifting the effective exposure boundary E _B outside It has become.
The above point will be described more specifically with reference to exposure control data. FIG. 8 is a diagram schematically showing exposure control data in the DI exposure apparatus of the embodiment.
The exposure control data includes information on exposure points required on the surface of the object W. For the sake of understanding, it is assumed that the optical axis of the projection optical system (not shown in FIG. 8) is in the vertical direction (Z direction). Further, it is assumed that the object W is a rectangular plate-like object whose sides extend along the XY direction. Further, it is assumed that the moving direction by the moving mechanism 2 is the X direction.

The exposure point required is specified by XY coordinates based on a specific position on the surface of the object W. Now, assume that the coordinates (X _m , Y _m ) of a certain exposure point M are specified. Further, it is assumed that a certain exposure point M is a place where four multiplexes (four times exposure) should be performed.
In this case, the exposure point M is exposed at four corresponding coordinates G ₁ to G ₄ on the line (scan line) SL along which the exposure point M travels. That is, as shown in FIG. 8A, the light of the pixel pattern S is irradiated at four corresponding coordinates G ₁ to G ₄ located on the scan line SL. This means that the four pixel mirrors 42 corresponding to the four corresponding coordinates are in the on state. In FIG. 8 (1), the four pixel mirrors 42 are shown to be in an ON state at the same time, but this is for the sake of understanding. It suffices if the on state is reached when G ₁ to G ₄ are reached.

In the above example, for example, the exposure point N adjacent to the exposure point M requires three multiple exposures (three exposures), and the exposure point N corresponds to the scan line SL with respect to the exposure point M. Suppose that it is located in the upper rear. In this case, as shown in FIG. 8 (2), at the stage of main exposure point N has reached the end of the corresponding coordinate G _4, pixel mirrors 42 corresponding to the corresponding coordinate G ₄ are being changed to off state, Therefore, the fourth exposure is not performed.

As described above, the exposure control data is set as data indicating whether the pixel mirror 42 corresponding to the corresponding coordinate is in the on state or the off state at the timing when each exposure point reaches the corresponding coordinate. The “timing when each corresponding coordinate is reached” corresponds to the movement by the movement mechanism 2. The moving speed in the moving mechanism 2 is a fixed and known value, and the ON / OFF sequence of each pixel mirror 42 corresponding thereto is exposure control data.

A more specific example of exposure control data for performing multiple exposure will be described. FIG. 9 is a schematic diagram showing an example of exposure control data in the DI exposure apparatus of the embodiment.
FIG. 9 (1) shows a part of the shape to be exposed on the surface of the object W. In this example, exposure is performed with a pattern of lines (circuit lines) having a certain width extending obliquely. A region filled with gray is a shape to be exposed, and this is a design exposure pattern. In FIG. 9 (1), the black circles indicate exposure points.
FIG. 9B is a bar graph showing the multiplicity on each scan line SL when exposure is performed in the shape as shown in FIG.

In the embodiment, the number of exposures at each exposure point is set according to the distance to the boundary (gray area) of the design exposure pattern. For exposure points that require a distance to the boundary that is equal to or greater than the exposure point pitch, the maximum number of exposures (4 multiplexes) is set. For exposure points that require a distance to the boundary of the design exposure pattern that is less than the exposure point pitch, the number of exposures is less than the maximum number depending on the distance to the boundary.

More specifically, each exposure point on the scan line a is exposed to the maximum number of times (4 multiplexes) because the distance to the boundary of the design exposure pattern is equal to or greater than the exposure point pitch. The same applies to each exposure point on the scan line e.
Of the exposure points required on the scan line b, the central four exposure points are equal to or greater than the exposure point pitch to the boundary, so that the number of exposure points at the left end is one multiplex (one time). Exposure). For this reason, as shown in FIG. 9 (1), exposure is performed by protruding to the left by 1/4 of the exposure point pitch D. The exposure point at the right end is triple (3 exposures). Therefore, as shown in FIG. 9 (1), the exposure point protrudes to the right by 3/4 of the exposure point pitch D and is effectively exposed.

Similarly, on the scan line c, the four exposure points at the center are equal to or larger than the exposure point pitch to the boundary, so that the number of exposure points at the left and right ends is doubled (four times). 2 times exposure). For this reason, the exposure is effectively performed by projecting by 1/2 of the exposure point pitch D on each of the left and right sides.
Further, on the scan line d, the four exposure points at the center are equal to or larger than the exposure point pitch to the boundary, so that the number of exposure points at the left end is three times (three times exposure). The right-most exposure point is one multiple (one exposure). For this reason, the exposure is effectively performed by protruding by 3/4 of the exposure point pitch D at the right end and by protruding by 1/4 of the exposure point pitch D at the right end.

FIG. 9 (3) is a diagram showing the multiplicity shown in FIG. 9 (2) as control data. By selecting the multiplicity at each exposure point as shown in FIG. 9 (3), exposure is performed with a circuit line pattern of a certain width extending obliquely as shown in FIG. 9 (1).
A sequence program in which exposure control data is incorporated is installed in the storage unit 71 of the main control unit 7. The sequence program is sent to the modulator controller 41, and the spatial light modulator 4 is controlled by a sequence based on the multiplicity data. As a result, each exposure point is exposed with multiplicity as shown in FIG. In the sequence program, in addition to the above, data on the placement position of the object W with respect to the reference point on the stage 21, data on each exposure point on the surface of the object W with respect to the reference point on the stage 21, movement of the stage 21 Speed data etc. are incorporated.

The selection of the multiplicity described above will be described in some detail. For each exposure point in the design exposure pattern, a rectangular area centering on each exposure point and having one side of twice the exposure point pitch D is considered. Then, it is determined whether or not there is a design exposure pattern boundary in this region. If there is a boundary, the distance (distance in the X direction or Y direction) from the relevant exposure point to the boundary is calculated, and this is any one of 1/4, 1/2, and 3/4 of the exposure point pitch D. Determine if it is closest to the value. Then, the multiplicity is selected according to the closest value. That is, if it is 1/4, it is 1 multiplexing (1 time exposure), if it is 1/2, it is 2 multiplexing (2 times exposure), if it is 3/4, it is 3 multiplexing (3 multiplexing). When the distance to the boundary is equal to the exposure point pitch D, or all the exposure points requiring no boundary of the design exposure pattern in the region are four multiplexes. Further, when the distance from the exposure point to the boundary is smaller than 1/8 of the exposure point pitch D, the exposure point is regarded as being on the boundary and 0 multiple (0 exposure) is performed. In this way, the multiplicity is selected for each exposure point and is incorporated into the exposure control data.

Next, the overall operation of the DI exposure apparatus according to the embodiment will be described. The following description is also a description of an embodiment of the DI exposure method invention. In the following description, it is assumed that the object W is a work for manufacturing a printed circuit board as described above.
In FIG. 1, the object W is placed on the stage 21 at the load position, and is vacuum-sucked on the stage 21 as necessary. Next, the moving mechanism 2 operates to move horizontally toward the exposure area E below each exposure unit 1. This moving direction coincides with one arrangement direction of the corresponding coordinates with high accuracy.

The moving mechanism 2 moves the stage 21 at a predetermined speed. At the time when the exposure point on the surface of the object W on the stage 21 reaches the corresponding coordinate, the pixel mirror 42 corresponding to the corresponding coordinate is turned on, and the exposure point is exposed.
The moving mechanism 2 continues to move the stage 21 in the same direction. When the required exposure point reaches the next corresponding coordinate, if the required exposure point is two or more places, the pixel mirror 42 corresponding to the corresponding coordinate is turned on, and the second exposure is performed. Done.

In this way, when each exposure point reaches the corresponding coordinates, the pixel mirror 42 is turned on or off according to the multiplicity of the required exposure point, and each exposure point is exposed with the determined multiplicity. The When the object W passes under each exposure unit 1, exposure at each exposure point is completed, and the surface of the object W including each exposure point has a desired exposure pattern as shown in FIG. This is the exposure.
Thereafter, when the stage 21 reaches the unload position, the movement of the stage 21 stops, and the exposed object W is picked up from the stage 21. And the target object W is conveyed to the place where the next process (for example, development process) is performed.

According to the above-described DI exposure apparatus and DI exposure method, multiple exposure is used in which the same exposure point is exposed multiple times, and the size of the exposed area is adjusted by multiple exposures at the periphery of the pixel pattern. Therefore, the size of the exposed area can be adjusted more finely than the exposure point pitch D. That is, the exposure resolution is increased. Therefore, exposure can be performed with a high-definition pattern that is more faithful to the design exposure pattern. For this reason, it is possible to obtain an effect that exposure of a smooth contour shape is possible while suppressing jaggies as much as possible, and fine adjustment of an exposure pattern such as line width change can be made finer. At this time, since it is not necessary to make the pixels of the spatial light modulator 4 finer, the cost is not particularly increased and the introduction is easy.
Further, it is not necessary to slow down the moving speed of the object W, and it is only necessary to change the control data (on / off data) of each pixel mirror 42 when each exposure point reaches the corresponding coordinates. For this reason, productivity does not decrease at all. Note that the amount of exposure control data is not particularly increased, and data processing is not complicated.

In the above embodiment, 4 when performing multiple (four exposure) is just essential exposure point adjacent to the effective exposure boundary E _B configuration, even those performing the exposure unit 1 is exposed in such illuminance It was. However, this is an example and other configurations are naturally possible. For example, to perform the more multi sure you lower the illumination of a pixel pattern, increases the number of effective exposure boundary E _B which can be taken in between the two corresponding coordinate can be increased more resolution.

Note that the illuminance distribution in the pixel pattern has been described as being a Gaussian distribution, but it need not be a complete Gaussian distribution and may be a distribution other than a Gaussian distribution. What is required is that the two pixel patterns are low in the peripheral portion where they overlap each other and high in the central portion where they do not overlap (higher than the peripheral portion), and such a distribution can be implemented.

In the DI exposure apparatus and the DI exposure method of the above embodiment, the movement of the object W is continuous, and exposure is performed with each pixel pattern without stopping. However, exposure may be performed by moving the object W intermittently while stopping the object W at a predetermined position. For example, there may be a case where the object W is stopped in a state where the required exposure point coincides with the corresponding coordinates, and exposure is performed in this state.

In addition, it has been described that exposure is performed when the stage 21 passes under each exposure unit 1 once, but the stage 21 reciprocates below the exposure unit 1 and exposure is performed in both of them. There is also a possibility.
The movement of the object W is sufficient if it is relative to the light of the irradiated exposure pattern. In addition to the case where the object W moves as described above, the object W is exposed to the stationary object W. The pattern may move. For example, a configuration in which the exposure unit 1 moves with respect to the stationary object W may be used.

Further, in the configuration of the DI exposure apparatus, it is not essential that there are a plurality of exposure units 1, and only one exposure unit 1 may be used. This is a configuration that is possible when the object W is small or when the large spatial light modulator 4 is employed.
In the above description, the object W is a work for manufacturing a printed circuit board. However, the DI exposure apparatus and the DI exposure method of the present invention can be employed in exposure techniques for other applications. For example, the DI exposure technique of the present invention can be employed in photolithography in the manufacture of a fine structure such as a micromachine (so-called MEMS).

DESCRIPTION OF SYMBOLS 1 Exposure unit 2 Moving mechanism 21 Stage 3 Light source 4 Spatial light modulator 41 Modulator controller 42 Pixel mirror 5 Projection optical system 6 Irradiation optical system 7 Main control part 71 Storage part W Object S Pixel pattern E _B Effective exposure boundary D Exposure Point pitch

Claims (4)

An exposure unit that irradiates the exposure area with light in a pattern according to the design exposure pattern; and
A moving mechanism that relatively moves through the exposure area an object having a photosensitive layer that is exposed to light when exposed to a critical exposure amount or more;
The exposure unit
The light source is disposed at a position where light from the light source is irradiated, and is either an on state where light is directed toward the exposure area or an off state where light is not directed toward the exposure area A spatial light modulator that spatially modulates the light from the light source so that the light irradiated to the exposure area having a large number of pixels has a pattern according to the design exposure pattern, and spatially by the spatial light modulator A direct imaging exposure apparatus comprising an optical system for projecting modulated light onto an exposure area,
A modulator controller for controlling each pixel of the spatial light modulator;
A storage unit that stores exposure control data that is data for on / off control of each pixel by the modulator controller;
Corresponding coordinates corresponding to each pixel of the spatial light modulator are set in the exposure area,
On the surface of the object, exposure points are set as indicating the locations to be exposed, and each exposure point is a point separated from each other by an exposure point pitch distance,
The optical system projects a pixel pattern of the pixel on each corresponding coordinate corresponding to each pixel in the on state of the spatial light modulator,
In the moving mechanism, the position of one exposure point of the target object is exposed by the pixel pattern on the scan line along the moving direction and is also superimposedly exposed by the peripheral portion of the pixel pattern on the adjacent scan line. The illuminance distribution in each pixel pattern is a distribution that is high in the central part and low in the peripheral part,
The exposure control data is positioned a predetermined number of times including the same exposure point on the surface of the target object once and twice or more at the corresponding coordinates on which the pixel pattern is projected as the target object is moved by the moving mechanism. To be exposed,
The predetermined number of times in the exposure control data is the maximum number when the distance to the design exposure pattern boundary is an exposure point requiring an exposure point pitch or more, and the distance to the design exposure pattern boundary is less than the exposure point pitch. A direct imaging exposure apparatus characterized in that at a certain exposure point, the number of times is less than the maximum number set according to the distance to the boundary. 2. The direct imaging exposure apparatus according to claim 1, wherein the spatial light modulator is a digital mirror device. Light from a light source is applied to a spatial light modulator having a large number of pixels that are either in an on state where light is directed toward the exposure area or in an off state where light is not directed toward the exposure area. A modulator irradiation step,
A modulator control step of controlling the spatial light modulator to control the spatial light modulator so that the light irradiated to the exposure area becomes a pattern according to the design exposure pattern;
A projection step of projecting light from the spatial light modulator onto an exposure area by an optical system;
A direct imaging exposure method comprising: a moving step of relatively moving an object having a photosensitive layer formed on the surface thereof exposed by exposure exceeding a critical exposure amount through an exposure area;
Corresponding coordinates corresponding to each pixel of the spatial light modulator are set in the exposure area,
On the surface of the object, exposure points are set as indicating the locations to be exposed, and each exposure point is a point separated from each other by an exposure point pitch distance,
The projecting step is a step of projecting a pixel pattern of the pixel on each corresponding coordinate corresponding to each pixel that is in the on state of the spatial light modulator,
In the projection step and the movement step, the position of one exposure point of the object is exposed by the pixel pattern on the scan line along the movement direction, and is also superimposed by the peripheral portion of the pixel pattern on the adjacent scan line. It is a step of moving the object so as to be exposed, and the illuminance distribution in each pixel pattern is a distribution that is high in the central part and low in the peripheral part,
The modulator control step and the moving step are predetermined in which the same required exposure point on the surface of the object includes one time and two times or more at the corresponding coordinates on which the pixel pattern is projected as the object is moved by the moving mechanism. It is a step to be exposed at a number of times,
The predetermined number of times in the exposure control data is the maximum number of exposure points where the distance to the boundary of the design exposure pattern is greater than or equal to the exposure point pitch, and the distance to the boundary of the design exposure pattern is less than the exposure point pitch. A direct imaging exposure method characterized in that the number of exposure points is less than the maximum number set according to the distance to the boundary. 4. The direct imaging exposure method according to claim 3, wherein the spatial light modulator is a digital mirror device.

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