JP7023601B2 - Direct imaging exposure equipment and direct imaging exposure method - Google Patents

Description

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

The exposure technique of exposing an object having a photosensitive layer formed on its surface to expose the photosensitive layer to light is actively used as a main technique of photolithography for forming various fine circuits and fine structures. In a typical exposure technique, light is applied to 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 applied to the object. do.

Apart from the exposure technique using such a mask, a technique of directly forming an image on the surface of an object by using a spatial light modulator and exposing it is known. Hereinafter, this technique is referred to as direct imaging exposure and abbreviated as DI exposure in the present specification.
In 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 right-angled grid pattern. Each mirror is designed so that the angle with respect to the optical axis is controlled independently, and it takes a posture in which the light from the light source is reflected to reach the object and a posture in which the light from the light source does not reach the object. It is supposed to get. The DMD includes a controller that controls each mirror, and the controller controls each mirror according to an exposure pattern so that the surface of the object is irradiated with the light of the exposure pattern.

In the case of DI exposure, since a mask is not used, an advantage is exhibited 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. In addition, when replacing the mask for the production of different types, it is necessary to stop the operation of the device, and it takes time and effort to restart the operation. Therefore, it becomes a factor that reduces productivity. On the other hand, in the case of DI exposure, it is only necessary to prepare the control data of each mirror for each product type, and when manufacturing different types of products, it is possible to respond only by changing the control data, which is advantageous in terms of cost and productivity. The sex is remarkable. Further, it is possible to finely adjust the exposure pattern for each work (exposure object) as needed, and it is also excellent in process flexibility.

As the spatial light modulator, in addition to the above-mentioned DMD which is a reflection type, a transmission type is also being studied. A typical transmissive spatial light modulator is an application of a transmissive liquid crystal display element, in which the transmission / blocking of light is controlled by the arrangement of the liquid crystal in each cell, and the light of the exposure pattern is emitted to the object. It is intended to be irradiated.
In the following description, each part of the spatial light modulator that reflects or transmits light to reach the object is referred to as a pixel. In the case of a reflective spatial light modulator, the pixel is each mirror, and in the case of a transmissive spatial light modulator, it is each 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 is not allowed to reach the object is referred to as an off state.

Japanese Unexamined Patent Publication No. 2004-355006

Although DI exposure has the above-mentioned advantages, it also has drawbacks peculiar to digital technology. One of them is the limit of exposure resolution. In DI exposure, it is not possible to perform exposure finer than the projection magnification of the pixel size of each pixel of the spatial light modulator. In this respect, it can be said that the exposure cannot be faithfully performed according to the exposure pattern as the design information (the pattern to be exposed to the object in the design of the product, hereinafter referred to as the design exposure pattern). The design exposure pattern is, for example, a design pattern of a circuit formed on a printed circuit board when the 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 the vector image data cannot be used to control the on / off of each pixel of the spatial light modulator. In this case, the data resolution of the raster image can be as fine as the pixel size of the spatial light modulator × the projection magnification. This is because even if the data resolution is made higher than that, it is meaningless because it cannot be expressed by the spatial light modulator.

On the other hand, the data of the design exposure pattern is often the 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 is inevitably "coarse". Along with this, some problems arise.
This point will be described with reference to FIGS. 10 and 11. 10 and 11 are diagrams showing a problem 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 jaggies generation. FIG. 10 (1) shows an example of a design exposure pattern, and FIG. 10 (2) shows a raster image generated from the design exposure pattern of (1). As shown in FIG. 10 (1), it is assumed that the design exposure pattern has an oblique boundary. "Slanting" means that the spatial light modulator is slanted with respect to the pixel arrangement direction. In this case, when the design exposure pattern is binarized into a raster image, jaggies occur at the diagonal boundary as shown in FIG. 10 (2).
When jaggies occur, for example, when exposure is performed for the formation of a fine circuit, there is a problem that unnecessary radiation (noise) is likely to occur in the formed fine circuit. Also, in general, if the pattern formed by exposure has jaggies, it looks bad. Therefore, it is required in DI exposure to form a pattern having a smooth contour shape with as little jaggy as possible.

Further, there is a problem that the degree of freedom of changing the exposure pattern is low in relation to the conversion to the raster image. FIG. 11 schematically shows this.
Design exposure patterns often include linear portions, such as the formation of microcircuits. 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 set to 8.4 pixels, so the line width is set to 8 pixels as shown in FIG. 11 (1). In this case, for example, if you want to change the line width to 7.4 pixels in the design exposure pattern, it will be rounded to 7 pixels in the raster image. In this case, the center position (center position in the width direction) of the line should not be changed in many cases, so that the line width becomes 6 pixels as shown in FIG. 11 (2). That is, the line becomes 1.4 pixels thinner than the design exposure pattern.

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

The present invention has been made to solve such a problem of DI exposure, and when the spatial light modulator is controlled and exposed according to the design exposure pattern, the pattern of the emitted light is the design exposure. The aim is to provide superior technology that can effectively increase the resolution beyond the limits of conventional resolution to get as close as possible to the pattern.

In order to solve the above problems, the invention according to claim 1 of the present application comprises an exposure unit that irradiates an exposure area with light in a pattern according to a design exposure pattern.
It is equipped with a moving mechanism that relatively and continuously moves an object whose surface is formed with a photosensitive layer that is exposed to exposure when exposed to a critical exposure amount or more.
The exposure unit is
The light source is placed at a position where the light from the light source is irradiated, and is either an on state in which the light is directed toward the exposure area or an off state in which the light is not directed toward the exposure area. Spatial light modulators that spatially modulate the light from the light source so that the light that has a large number of pixels and illuminates the exposure area follows the design exposure pattern, and spatial light modulators A direct imaging exposure apparatus equipped with an optical system that projects modulated light onto an exposure area.
A modulator controller that controls each pixel of the spatial light modulator,
A storage unit that stores exposure control data, which is data for on / off control of each pixel by the modulator controller, is provided.
Spatial light modulators consist of a large number of pixels arranged in a right-angled grid.
Corresponding coordinates corresponding to each pixel of the spatial light modulator are set in the exposure area, and each corresponding coordinate corresponds to the position of each intersection of the right-angled grid .
On the surface of the object, exposure points are set to indicate the points to be exposed, and the exposure points are points separated from each other by the distance of the exposure point pitch.
The movement mechanism is a mechanism for continuously linearly moving an object in a movement direction perpendicular to the optical axis in the optical system, and scans along the movement direction as a line in which each exposure point of the object moves during movement. The line is set and
Each exposure point is lined up in the moving direction, and is also lined up in the direction perpendicular to the optical axis and in the direction perpendicular to the moving direction, and multiple scan lines are set in parallel.
The optical system projects a pixel pattern by the pixel on each corresponding coordinate corresponding to each pixel in the ON state of the spatial light modulator.
The pixel patterns do not overlap each other and
The exposure control data is a pixel pattern arranged in the X direction when a certain direction perpendicular to the optical axis is the X direction and a direction perpendicular to the optical axis and also perpendicular to the X direction is the Y direction in the arrangement of each pixel pattern. Each column of is arranged not on the same straight line in the Y direction with respect to the pixel pattern of the adjacent column in the X direction, and each pixel pattern in the column in the X direction is adjacent to each other in the adjacent column in the X direction. It is data that turns each pixel on and off so that it is located at the position in the X direction between one pixel pattern.
The moving direction is a direction along the X direction.
The width of each pixel pattern in the Y direction is narrower than twice and wider than 1 times the separation interval of each scan line, and when the object is moved by the moving mechanism, the exposure point pitch is centered on the exposure point and one side. The square area to be exposed is exposed by the pixel pattern on the scan line passing through the exposure point, and is also exposed in an overlapping manner 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.
In the exposure control data, a maximum number of times and a number of times less than the maximum number of times and including one and two times are set as a predetermined number of times, and the exposure control data is obtained as the object is moved by the moving mechanism. The same exposure point on the surface of the object is positioned at the corresponding coordinates on which the pixel pattern is projected and exposed a predetermined number of times.
The predetermined number of times is the maximum number of times when the distance to the boundary of the design exposure pattern is equal to or greater than the exposure point pitch, and the distance to the boundary of the design exposure pattern is less than the exposure point pitch. Has a configuration in which the number of times is less than the maximum number of times (excluding 0 times) set according to the distance to the boundary (excluding 0 times).
Further, in order to solve the above problems, the invention according to claim 2 has a configuration in which the spatial light modulator is a digital mirror device in the configuration according to claim 1.
Further, in order to solve the above problem, the invention according to claim 3 is either an on state in which the light is directed toward the exposure area or an off state in which the light is not directed toward the exposure area. A modulator irradiation step of irradiating a spatial light modulator having a large number of pixels with light from a light source,
A modulator control step that controls the spatial light modulator so that the light shining on the exposure area follows the design exposure pattern.
A projection step that projects the light from the spatial light modulator onto the exposure area by optical system,
It is a direct imaging exposure method including a moving step of moving an object having a photosensitive layer formed on the surface of the surface, which is exposed to exposure by an exposure amount equal to or more than a critical exposure amount, relatively and continuously through an exposure area. ,
Spatial light modulators consist of a large number of pixels arranged in a right-angled grid.
Corresponding coordinates corresponding to each pixel of the spatial light modulator are set in the exposure area, and each corresponding coordinate corresponds to the position of each intersection of the right-angled grid .
On the surface of the object, exposure points are set to indicate the points to be exposed, and the exposure points are points separated from each other by the distance of the exposure point pitch.
The movement step is a step of continuously linearly moving an object in a moving direction perpendicular to the optical axis in the optical system, and scans along the moving direction as a line in which each exposure point of the object moves during movement. The line is set and
Each exposure point is lined up in the moving direction, and is also lined up in the direction perpendicular to the optical axis and in the direction perpendicular to the moving direction, and multiple scan lines are set in parallel.
The projection step is a step of projecting a pixel pattern by the pixel on each corresponding coordinate corresponding to each pixel in the ON state of the spatial light modulator.
The pixel patterns do not overlap each other and
In the arrangement of each pixel pattern, the modulator control step is a pixel arranged in the X direction when a certain direction perpendicular to the optical axis is the X direction and a direction perpendicular to the optical axis and also perpendicular to the X direction is the Y direction. Each column of the pattern is arranged not on the same straight line in the Y direction with respect to the pixel pattern of the adjacent X-direction column, and each pixel pattern in the X-direction column is adjacent to each other in the adjacent X-direction column. It is a step to turn each pixel on and off so that it is located at the position in the X direction between the two pixel patterns.
The moving direction is a direction along the X direction.
The width of each pixel pattern in the Y direction is narrower than twice and wider than 1 times the separation interval of each scan line, and the projection step and the movement step are squares centered on the exposure point and with the exposure point pitch as one side. Is a step in which the region of is exposed by the pixel pattern on the scan line passing through the exposure point and is also exposed in an overlapping manner 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.
In the modulator control step and the moving step, a maximum number of times and a number of times less than the maximum number of times and including one and two times are set as predetermined times, and the modulator control step and the moving step are performed by the moving mechanism. It is a step of making the same exposure point on the surface of the object positioned at the predetermined number of times to be exposed at the corresponding coordinates on which the pixel pattern is projected as the object moves.
The predetermined number of times is the maximum number of times at the exposure required point where the distance to the boundary of the design exposure pattern is equal to or larger than the exposure point pitch, and is the maximum number of times at the exposure required point where the distance to the boundary of the design exposure pattern is less than the exposure point pitch. It has a configuration that the number of times is less than the maximum number of times (excluding 0 times) set according to the distance to the boundary (excluding 0 times).
Further, in order to solve the above problems, the invention according to claim 4 has a configuration in which the spatial light modulator is a digital mirror device in the configuration of claim 3.

As described below, according to the invention of this application, multiple exposure is adopted in which the same exposure point is exposed multiple times, 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 effective size of the exposed area can be adjusted more finely. Therefore, the effective exposure resolution is improved.

It is a schematic diagram of the direct imaging exposure apparatus of an embodiment. It is a schematic diagram of the exposure unit provided in the apparatus shown in FIG. It is a perspective schematic diagram which showed the exposure area by each exposure unit. It is a perspective view which showed each pixel pattern and the illuminance distribution of each pixel pattern roughly. It is a figure which showed conceptually about the multiple exposure. It is a figure which showed conceptually about the multiple exposure. It is a figure which showed an example of the photosensitive characteristic of a photosensitive layer. It is a figure which showed schematically about the exposure control data in the DI exposure apparatus of embodiment. It is a schematic diagram which showed an example of the exposure control data in the DI exposure apparatus of embodiment. It is a figure which showed the problem of DI exposure technique. It is a figure which showed the problem of DI exposure technique.

Next, an embodiment for carrying out the claimed invention (hereinafter referred to as an embodiment) will be described.
First, an embodiment of the invention of the DI exposure apparatus will be described. FIG. 1 is a schematic view of the DI exposure apparatus of the 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 an object W through the exposure area.
The DI exposure apparatus of this embodiment is an apparatus for manufacturing a printed circuit board. Therefore, in the object W, a conductive film for wiring is formed on a substrate, and a photosensitive layer is formed on the conductive film. The photosensitive layer is a coated resist film.

FIG. 2 describes the exposure unit 1 included in the apparatus shown in FIG. FIG. 2 is a schematic view of the exposure unit 1 included in the apparatus shown in FIG. As shown in FIG. 2, the exposure unit 1 has a light source 3, a spatial light modulator 4 that spatially modulates the light from the light source 3, and optics that project an image of light modulated by the spatial light modulator 4. It is equipped with a system (hereinafter referred to as a projection optical system) 5 and the like.

As the light source 3, a light source 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 in the visible short wavelength region to the ultraviolet region, and as the light source 3, a light source that outputs light in the visible short wavelength region to the ultraviolet region such as 405 nm or 365 nm is used. Further, in order to utilize the performance of the spatial light modulator 4, it is preferable that the spatial light modulator 4 outputs coherent light, and therefore a laser light source is preferably used. For example, a gallium nitride (GaN) -based semiconductor laser is used.

As the spatial light modulator 4, DMD is used in this embodiment. 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, for example, a square mirror having a size of about 13.68 μm square, and has a structure in which a large number of pixel mirrors are arranged in a right-angled grid pattern. The number of sequences is, for example, 1024 × 768.

The spatial light modulator 4 includes a modulator controller 41 that controls each pixel mirror. The DI exposure apparatus of the embodiment includes a main control unit 7 that controls the whole. The modulator controller 41 controls each pixel mirror according to the signal from the main control unit 7. In addition, each pixel mirror has a plane in which each pixel mirror is arranged as a reference plane, a first posture along the reference plane, and a second tilted at, for example, about 11 to 13 ° with respect to the reference plane. You can take a posture. In this embodiment, the first posture is in the off state and the second posture is in the on state.
The spatial light modulator 4 includes a drive mechanism for driving each pixel mirror, and the modulator controller 41 independently controls whether to take the first posture or the second posture for each pixel mirror. You can do it. 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 such a spatial light modulator 4 with light from a light source 3. 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 perform accurate image formation using the spatial light modulator 4 which is a DMD, it is desirable to incident parallel light and reflect it on each pixel mirror 42, and to be oblique to each pixel mirror 42. It is desirable to inject light. Therefore, as shown in FIG. 2, the irradiation optical system 6 is for obliquely incident light on the collimator lens 62 that emits light emitted from each optical fiber 61 and spreads as parallel light, and the spatial light modulator 4. It is equipped with a reflection mirror 63. "Slanting" means diagonally with respect to the reference plane of the spatial light modulator 4. The angle of incidence θ with respect to the reference plane is, for example, an angle of about 22 to 26 °.

The projection optical system 5 is composed of two projection lens groups 51 and 52 and a microlens array (hereinafter abbreviated as MLA) 53 and the like arranged between the projection lens groups 51 and 52. The MLA 53 is supplementarily arranged 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-angled grid pattern. Each lens element has a one-to-one correspondence with each pixel mirror of the spatial light modulator 4.

In the exposure unit 1 described above, the light from the light source 3 is guided by the optical fiber 61 and then incident on 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 the posture is selectively tilted 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 that. The light reflected by the pixel mirror in the off state does not reach the exposure area, but only the light reflected by the pixel mirror in the on state reaches. Therefore, the light of the pattern according to the design exposure pattern is applied to the exposure area.

On the other hand, as shown in FIG. 1, the DI exposure apparatus of the embodiment includes a stage 21 on which the object W is placed. The moving mechanism 2 is a mechanism for linearly moving 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 servomotor 24 for rotating the ball screw 22, and the like is adopted. In addition, a linear motor stage or the like that linearly moves the stage 21 by utilizing the action of magnetism may be used. The stage 21 supports the object W so that it does not move by a method such as vacuum suction. In order to reduce the contact area with the work 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 the 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 by the moving mechanism 2. One column is arranged so as to be offset 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 any 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 how the object W reaching below each exposure unit 1 is exposed. In FIG. 3, the exposure area E by each exposure unit 1 is shown 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 the exposure is performed with that pattern.
The object W is irradiated with the pattern formed in each exposure area E while moving in the direction indicated by the arrow in FIG. 3 (X direction). At this time, since the two rows of exposure units 1 are arranged so as to be offset from each other, exposure is performed without a gap even in the horizontal direction perpendicular to the moving direction.

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

The exposure control data is closely related to the light irradiation pattern (hereinafter referred to as 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 of the embodiment uses the DMD as the spatial light modulator 4, and the projection optical system 5 displays the pixel pattern S by each pixel mirror 42 in the on state as shown in FIG. Project. The projection position of each pixel pattern S is the position of each corresponding coordinate G set in the exposure area. The 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 the right-angled grid having an aspect ratio of 1.

The distance between the 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 less than 1, the inter-coordinate distance is shorter than one side of the pixel mirror 42. In the case of exposure for manufacturing a printed circuit board, the magnification is often larger than 1. In the embodiment, the shape of each pixel mirror 42 is square, but the image (pixel pattern) by the projection optical system 5 is a rounded image (almost circular image).

The object W moves in the horizontal direction by the moving mechanism 2. At the time of this movement, the object W passes through the irradiation point of each pixel pattern S and is exposed. The exposure-required portion of the object W is specified by XY coordinates with respect to a specific position on the surface of the object W. These coordinates are hereinafter referred to as exposure-required points and are indicated by M. Each exposure point M has a grid pattern and is separated by a certain 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 is moved 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 shown by the alternate long and short dash 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 may be in an oblique direction with respect to the XY direction.

As shown in FIG. 4, when a certain exposure point M moves through a certain scan line SL and passes through the pixel pattern S, the exposure unit region centered on the exposure point M is the adjacent scan line SL. It is also exposed by the pixel pattern S'above. That is, although there is a slight time lag, since it passes through the peripheral portion of the pixel pattern S'of the adjacent scan line SL, it is also exposed by the peripheral portion. That is, the moving mechanism 2 moves the object M so that each exposure unit area is exposed by the pixel pattern on the scan line SL and is also exposed in an overlapping manner by the peripheral portion of the pixel pattern on the adjacent scan line SL. It is a mechanism to make it. The exposure unit region is a region on the surface of the object W specified by the exposure required point M, and is a region centered on the exposure required point M. This area is a rectangular area with the exposure point pitch as one side.

In FIG. 4, the illuminance distribution according to the pixel pattern S is shown as I, and the illuminance distribution according to the pixel pattern S'is shown as I'. As shown in FIG. 4, the illuminance distributions I and I'in each of the pixel patterns S and S'are high in the non- overlapping portion and low in the overlapping portion. 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. The illuminance distribution I is symmetrical with respect to the center of the pixel pattern (corresponding coordinate G), and has a distribution as shown in FIG. 4 in any horizontal direction.

The DI exposure apparatus of the embodiment optimizes the exposure control data on the premise that the light irradiation pattern by each pixel mirror and the illuminance distribution thereof are as described above. More specifically, for a portion of the surface of the object W that requires exposure of a predetermined amount or more (exposure-required portion), a predetermined number of exposures including once and twice or more (hereinafter referred to as multiple exposure) is performed. The number of exposures is optimized in order to improve the effective resolution.

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

First, for comparison, a normal exposure other than multiple exposure will be described. FIG. 5 (1) is the same as FIG. 4, and shows the exposure amount of each pixel pattern projected on the continuous exposure-required points. Since it is a single exposure, the exposure amount has the same distribution as the illuminance distribution I of each pixel pattern.
The exposure amount obtained by integrating each exposure amount shown on the left side of FIG. 5 (1) is the actual exposure amount, and it 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 exposed parts 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 "single multiple exposure". The two exposures are referred to as "double", the three exposures are referred to as "three multiplexes", and the four exposures are referred to as "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 the case of a negative resist as an example. As shown in FIG. 7, the photosensitive layer becomes zero (insoluble) _soluble in a developer at a certain critical exposure amount EC. Even if the exposure amount is increased further, the characteristics do not change. Hereinafter, such an exposure amount _EC is referred to as a critical exposure amount.

In FIG. 5 (1), the area integrated exposure amount is set to be equal to or _greater than the critical exposure amount EC at the corresponding coordinates where the light of the pixel pattern is irradiated. This is achieved by appropriately adjusting the illuminance (average illuminance or peak illuminance) in each pixel pattern. As shown in FIG. 6 , since the area integrated exposure amount is lower than the critical exposure amount at the position _EB outside the corresponding coordinates located at the end of the exposure-required points, this position _EB is the effective exposure. This is the edge of the area (hereinafter referred to as the effective exposure boundary).

Similarly, in the case of the multiple exposures of FIGS. 5 (1) to 5 (4), the area integrated exposure amount is shown on each right side. FIG. 6 is a diagram showing the area integrated exposure amount shown on the right side of each of FIGS. 5 (1) to 5 (4) in one graph for easy understanding.
In FIG. 6, the exposure-requiring point of the exposure-requiring portion located on the rightmost side of the exposure _- requiring portion is defined as G1. It is shown that the exposure-required points until reaching G1 are ₁ -multiplexed, 2-multiplexed, 3-multiplexed, and 4-multiplexed, respectively. Further, the exposure point pitch is indicated by D.

As shown in FIG. 6, the position of the effective exposure boundary _EB shifts outward as the degree of multiplexing increases, such as from 1-multiplex to 4-multiplex. In this example, one adjacent exposure required point ( _{G 2} ) reaches the critical exposure amount EC when four multiplex are performed. In other words, the number of effective exposure boundaries _EB has increased four times (three coordinates can be selected in between), which means that exposure can be performed with apparently four times the resolution.
In this example, in the case of one multiplex, the position P ₁ at a distance of 1/4 of the exposure point pitch D from the exposure required point ( _{G 1} ) located at the end reaches the critical exposure amount EC. There is. Therefore, if G ₁ is to be the effective exposure boundary, it is sufficient to make four multiplexes at the exposure required point (indicated by G ₀ ) immediately before G ₁ and set the exposure count to 0 for the exposure required point G ₁ . become. Hereinafter, the number of exposures of 0 is referred to as "0 multiplex" for convenience.

As described above, the DI exposure apparatus of the embodiment is an apparatus that improves the effective exposure resolution by exposing the selected exposure-required portion to two or more times and thereby shifting the effective exposure boundary _EB to the outside. It has become.
The above points will be described more specifically in line with the 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 an exposure-required portion on the surface of the object W. For understanding, the optical axis of the projection optical system (not shown in FIG. 8) is assumed to be in the vertical direction (Z direction). Further, it is assumed that the object W is a rectangular plate-shaped 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 is specified by the XY coordinates with respect to a specific position on the surface of the object W. Now, suppose that the coordinates (X _m , Y _m ) of a certain exposure point M are specified. Then, it is assumed that a certain exposure point M is a place where four multiplex (four exposures) should be performed.
In this case, the exposure _- required point M is exposed at the _four corresponding coordinates G1 to G4 on the line (scan line) SL on which the exposure-required point M advances. That is, as shown in FIG. 8 (1), the light of the pixel pattern S is irradiated at the _four corresponding coordinates G1 to _G4 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 drawn so as to be in the ON state at the same time, but this is for understanding, and in reality, the exposure point M is the corresponding coordinate. It suffices if it is turned _on when G1 to _G4 are reached.

In the above example, for example, it is assumed that three multiple exposures (three exposures) are required for the exposure required point N adjacent to the exposure required point M, and the exposure required point N is the scan line SL with respect to the exposure required point M. Suppose it is located behind the top. In this case, as shown in FIG. 8 (2), when the exposure point N reaches the final corresponding coordinate G ₄ , the pixel mirror 42 corresponding to the corresponding coordinate G ₄ is changed to the off state. Therefore, the fourth exposure is not performed.

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

A more specific example of the exposure control data for performing multiple exposure will be described. FIG. 9 is a schematic view 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. This example is an example of exposure with a pattern of lines (circuit lines) having a constant width extending diagonally. The area filled with gray is the shape to be exposed, and this is the design exposure pattern. In FIG. 9 (1), the portion indicated by the black circle is the exposure point.
FIG. 9 (2) is a bar graph showing the above multiplicity in each scan line SL when exposure is performed in the shape as shown in (1).

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. The maximum number of exposures (4 multiplexes) is set for all exposure points where the distance to the boundary is equal to or greater than the exposure point pitch. Then, for the exposure-required points where the distance to the boundary of the design exposure pattern is less than the exposure point pitch, the number of exposures is less than the maximum number according to the distance to the boundary.

Specifically, each exposure point on the scan line a is exposed at the maximum number of times (4 multiplexes) because the distance to the boundary of the design exposure pattern is equal to or larger than the exposure point pitch. The same applies to each exposure point on the scan line e.
Of the exposure points on the scan line b, the four exposure points in the center are at least the exposure point pitch up to the boundary, so they are multiplexed (four exposures), and the leftmost exposure point is one multiplex (one exposure). Exposure). Therefore, as shown in FIG. 9 (1), only 1/4 of the exposure point pitch D is exposed to the left side. At the rightmost exposure point, the number of exposure points is tripled (three exposures). Therefore, as shown in FIG. 9 (1), only 3/4 of the exposure point pitch D protrudes to the right and is effectively exposed.

Similarly, on the scan line c, the four exposure points in the center are four-multiplexed (four-exposure) because the exposure point pitch is equal to or higher than the boundary, and the four exposure-required points at the left and right ends are each double-multiplexed (four exposures). (Twice exposure). Therefore, the exposure is effectively performed by protruding only 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 in the center are similarly quadrupled (4 exposures) because the exposure point pitch is equal to or higher than the boundary, and the exposure points on the left end are 3 multiplex (3 exposures). The exposure point required at the right end is one multiplex (one exposure). Therefore, only 3/4 of the exposure point pitch D protrudes at the right end, and only 1/4 of the exposure point pitch D protrudes at the right end to be effectively exposed.

FIG. 9 (3) is a diagram showing the multiplicity shown in FIG. 9 (2) as data and control data. By selecting the multiplicity at each exposure point as shown in FIG. 9 (3), exposure is performed with a pattern of circuit lines having a constant width extending diagonally as shown in FIG. 9 (1).
A sequence program incorporating exposure control data is implemented 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 the multiplicity as shown in FIG. In addition to the above, the sequence program includes 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, and movement of the stage 21. Speed data etc. are incorporated.

To explain the selection of the multiplicity described above in a little more detail, for each exposure point in the design exposure pattern, a rectangular region centered on each exposure point and having twice the exposure point pitch D as one side is considered. Then, it is determined whether or not there is a boundary of the design exposure pattern in this region. If there is a boundary, the distance (distance in the X direction or Y direction) from the exposure required point to the boundary is calculated, and it is either 1/4, 1/2, or 3/4 of the exposure point pitch D. Determine if it is closest to the value. Then, the degree of multiplexing is selected according to the closest value. That is, if it is 1/4, it is 1 multiplex (1 exposure), if it is 1/2, it is 2 multiplex (2 times exposure), and if it is 3/4, it is 3 multiplex (3 multiplex). When the distance to the boundary is equal to the exposure point pitch D, or when there is no boundary of the design exposure pattern in the area, all the exposure points requiring exposure are quadrupled. When the distance from the exposure required point to the boundary is smaller than 1/8 of the exposure point pitch D, the exposure required point is regarded to be on the boundary and is set to 0 multiplex (0 exposure). In this way, the multiplicity is selected for each exposure point and incorporated into the exposure control data.

Next, the overall operation of the DI exposure apparatus of the embodiment will be described. The following description is also a description of the embodiment of the invention of the DI exposure method. In the following description, it is assumed that the object W is a workpiece 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 onto the stage 21 as needed. Next, the moving mechanism 2 operates and moves horizontally toward the exposure area E below each exposure unit 1. This movement direction accurately matches one of the arrangement directions of the corresponding coordinates.

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

In this way, when each exposure-required point reaches the corresponding coordinates, the pixel mirror 42 is turned on or off according to the multiplicity of the exposure-required portion, and each exposure-required point is exposed at a predetermined multiplicity. To. When the object W passes below each exposure unit 1, the exposure of 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. 9 (1). Has been exposed.
After that, when the stage 21 reaches the unload position, the movement of the stage 21 is stopped, and the exposed object W is picked up from the stage 21. Then, the object W is transported to a place where the next processing (for example, development processing) is performed.

According to the DI exposure apparatus and the DI exposure method described above, multiple exposures that expose the same exposure point multiple times are adopted, and the size of the exposed area is adjusted by multiple exposures by the peripheral portion 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 resolution of exposure becomes high. Therefore, it is possible to perform exposure 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 jaggies are suppressed as much as possible to enable exposure with a smooth contour shape, and fine adjustment of an exposure pattern such as a line width change can be performed. At this time, since it is not necessary to make the pixels of the spatial light modulator 4 fine, the cost does not increase in particular, 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. Therefore, the productivity does not decrease at all. The amount of exposure control data does not increase in particular, and the data processing is not complicated.

In the above embodiment, when four multiplexes (four exposures) are performed, the adjacent exposure point is the effective exposure boundary _EB , and each exposure unit 1 exposes with such an illuminance. rice field. However, this is just an example, and other configurations are of course possible. For example, if the illuminance of the pixel pattern is lowered and more multiplexing is performed, the number of effective exposure boundary _EBs that can be taken between the two corresponding coordinates increases, and the resolution can be further increased.

Although the illuminance distribution in the pixel pattern has been described as having a Gaussian distribution, it does not have to be a perfect Gaussian distribution, and may be a distribution other than the Gaussian distribution. What is required is that the two pixel patterns are low in the peripheral part where they overlap each other and high in the central part where they do not overlap (higher than the peripheral part), and such a distribution is feasible.

In the DI exposure apparatus and DI exposure method of the above-described embodiment, the object W moves continuously, and exposure is performed by each pixel pattern without stopping. However, although it is out of the scope of the present invention, there may be a case where the object W is intermittently moved and exposed while the object W is stopped at a predetermined position. For example, the object W may be stopped in a state where the exposure required point matches the corresponding coordinates, and exposure may be performed in this state.

Further, although it has been described that the exposure is performed when the stage 21 passes below each exposure unit 1 once, the case where the stage 21 reciprocates below the exposure unit 1 and the exposure is performed by both of them. Is also possible.
It is sufficient that the movement of the object W is relative to the light of the irradiated exposure pattern, and the object W is exposed to the stationary object W in addition to the case where the object W moves as described above. The pattern may move. For example, the exposure unit 1 may be configured to move as a whole with respect to the stationary object W.

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 configuration is possible when the object W is small or when a large spatial light modulator 4 is adopted.
In the above description, the object W is a work for manufacturing a printed circuit board, but the DI exposure apparatus and the DI exposure method of the present invention can also be adopted in exposure techniques for other applications. For example, the DI exposure technique of the present invention can be adopted in photolithography in the manufacture of microstructures such as micromachines (so-called MEMS).

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 unit 71 Storage unit 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 that follows the design exposure pattern,
It is equipped with a moving mechanism that relatively and continuously moves an object whose surface is formed with a photosensitive layer that is exposed to exposure when exposed to a critical exposure amount or more.
The exposure unit is
The light source is placed at a position where the light from the light source is irradiated, and is either an on state in which the light is directed toward the exposure area or an off state in which the light is not directed toward the exposure area. Spatial light modulators that spatially modulate the light from the light source so that the light that has a large number of pixels and illuminates the exposure area follows the design exposure pattern, and spatial light modulators A direct imaging exposure apparatus equipped with an optical system that projects modulated light onto an exposure area.
A modulator controller that controls each pixel of the spatial light modulator,
A storage unit that stores exposure control data, which is data for on / off control of each pixel by the modulator controller, is provided.
Spatial light modulators consist of a large number of pixels arranged in a right-angled grid.
Corresponding coordinates corresponding to each pixel of the spatial light modulator are set in the exposure area, and each corresponding coordinate corresponds to the position of each intersection of the right-angled grid .
On the surface of the object, exposure points are set to indicate the points to be exposed, and the exposure points are points separated from each other by the distance of the exposure point pitch.
The movement mechanism is a mechanism for continuously linearly moving an object in a movement direction perpendicular to the optical axis in the optical system, and scans along the movement direction as a line in which each exposure point of the object moves during movement. The line is set and
Each exposure point is lined up in the moving direction, and is also lined up in the direction perpendicular to the optical axis and in the direction perpendicular to the moving direction, and multiple scan lines are set in parallel.
The optical system projects a pixel pattern by the pixel on each corresponding coordinate corresponding to each pixel in the ON state of the spatial light modulator.
The pixel patterns do not overlap each other and
The exposure control data is a pixel pattern arranged in the X direction when a certain direction perpendicular to the optical axis is the X direction and a direction perpendicular to the optical axis and also perpendicular to the X direction is the Y direction in the arrangement of each pixel pattern. Each column of is arranged not on the same straight line in the Y direction with respect to the pixel pattern of the adjacent column in the X direction, and each pixel pattern in the column in the X direction is adjacent to each other in the adjacent column in the X direction. It is data that turns each pixel on and off so that it is located at the position in the X direction between one pixel pattern.
The moving direction is a direction along the X direction.
The width of each pixel pattern in the Y direction is narrower than twice and wider than 1 times the separation interval of each scan line, and when the object is moved by the moving mechanism, the exposure point pitch is centered on the exposure point and one side. The square area to be exposed is exposed by the pixel pattern on the scan line passing through the exposure point, and is also exposed in an overlapping manner 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.
In the exposure control data, a maximum number of times and a number of times less than the maximum number of times and including one and two times are set as a predetermined number of times, and the exposure control data is obtained as the object is moved by the moving mechanism. The same exposure point on the surface of the object is positioned at the corresponding coordinates on which the pixel pattern is projected and exposed a predetermined number of times.
The predetermined number of times is the maximum number of times when the distance to the boundary of the design exposure pattern is equal to or greater than the exposure point pitch, and the distance to the boundary of the design exposure pattern is less than the exposure point pitch. The direct imaging exposure apparatus is characterized in that the number of times is less than the maximum number of times (excluding 0 times) set according to the distance to the boundary (excluding 0 times). The direct imaging exposure apparatus according to claim 1, wherein the spatial light modulator is a digital mirror device. The light from the light source is applied to a spatial light modulator having a large number of pixels, which is either an on state in which the light is directed toward the exposure area or an off state in which the light is not directed toward the exposure area. Modulator irradiation step and
A modulator control step that controls the spatial light modulator so that the light shining on the exposure area follows the design exposure pattern.
A projection step that projects the light from the spatial light modulator onto the exposure area by optical system,
It is a direct imaging exposure method including a moving step of moving an object having a photosensitive layer formed on the surface of the surface, which is exposed to exposure by an exposure amount equal to or more than a critical exposure amount, relatively and continuously through an exposure area. ,
Spatial light modulators consist of a large number of pixels arranged in a right-angled grid.
Corresponding coordinates corresponding to each pixel of the spatial light modulator are set in the exposure area, and each corresponding coordinate corresponds to the position of each intersection of the right-angled grid .
On the surface of the object, exposure points are set to indicate the points to be exposed, and the exposure points are points separated from each other by the distance of the exposure point pitch.
The movement step is a step of continuously linearly moving an object in a moving direction perpendicular to the optical axis in the optical system, and scans along the moving direction as a line in which each exposure point of the object moves during movement. The line is set and
Each exposure point is lined up in the moving direction, and is also lined up in the direction perpendicular to the optical axis and in the direction perpendicular to the moving direction, and multiple scan lines are set in parallel.
The projection step is a step of projecting a pixel pattern by the pixel on each corresponding coordinate corresponding to each pixel in the ON state of the spatial light modulator.
The pixel patterns do not overlap each other and
In the arrangement of each pixel pattern, the modulator control step is a pixel arranged in the X direction when a certain direction perpendicular to the optical axis is the X direction and a direction perpendicular to the optical axis and also perpendicular to the X direction is the Y direction. Each column of the pattern is arranged not on the same straight line in the Y direction with respect to the pixel pattern of the adjacent X-direction column, and each pixel pattern in the X-direction column is adjacent to each other in the adjacent X-direction column. It is a step to turn each pixel on and off so that it is located at the position in the X direction between the two pixel patterns.
The moving direction is a direction along the X direction.
The width of each pixel pattern in the Y direction is narrower than twice and wider than 1 times the separation interval of each scan line, and the projection step and the movement step are squares centered on the exposure point and with the exposure point pitch as one side. Is a step in which the region of is exposed by the pixel pattern on the scan line passing through the exposure point and is also exposed in an overlapping manner 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.
In the modulator control step and the moving step, a maximum number of times and a number of times less than the maximum number of times and including one and two times are set as predetermined times, and the modulator control step and the moving step are performed by the moving mechanism. It is a step of making the same exposure point on the surface of the object positioned at the predetermined number of times to be exposed at the corresponding coordinates on which the pixel pattern is projected as the object moves.
The predetermined number of times is the maximum number of times at the exposure required point where the distance to the boundary of the design exposure pattern is equal to or larger than the exposure point pitch, and is the maximum number of times at the exposure required point where 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 times is less than the maximum number of times (excluding 0 times) set according to the distance to the boundary (excluding 0 times). The direct imaging exposure method according to claim 3, wherein the spatial light modulator is a digital mirror device.

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