JPH06324474A - Photomask and exposing method - Google Patents

Abstract

PURPOSE:To hardly perceive contrast difference caused on a connecting part in the case of performing exposure by picture synthesis. CONSTITUTION:The connecting parts 43 obtained in the case of performing exposure by the picture synthesis are exposed to be overlapped to each other's, and unit patterns arrayed on the connecting part 43 are discretely, irregularly, and selectively exposed so that the unit patterns may not be repeatedly exposed twice or more. Thus, even through the contrast difference exists between the unit patterns formed on the connecting part, the unit patterns having the contrast difference are mixed, so that the connecting part is hardly perceived.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Field of Industrial Application Conventional Technology (FIG. 4) Problem to be Solved by the Invention (FIGS. 5 to 8) Means for Solving the Problem (FIG. 1) Action Example (FIGS. 1 to 3)

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used in a projection exposure apparatus used for manufacturing a liquid crystal device or the like and an exposure method using this photomask, and is particularly suitable for application to screen synthesis for forming a large area pattern. It is something.

[0003]

2. Description of the Related Art Conventionally, an exposure apparatus 1 having an optical system as shown in FIG. 4 has been used as an exposure apparatus using this type of photomask. This exposure apparatus 1 uses an ellipsoidal mirror 3 to emit light emitted from an ultra-high pressure mercury lamp 2 which is a light source for exposure.
After the light is collected by the light source, the light is guided to the wavelength filter 5 via the reflection mirror 4.

The wavelength filter 5 is adapted to extract only the wavelength required for exposure, and is adapted to extract light having a wavelength generally called g-line or i-line. Wavelength filter 5
The light that has passed through is converted into a light flux having a uniform illuminance distribution by the fly-eye integrator 6 and illuminated on the blind 7. The blind 7 constitutes a rectangular diaphragm, and its size and position can be arbitrarily set.

Optically, the image of the blind 7 reflected by the reflecting mirror 8 is formed on the reticle 10 by the condenser lens 9 at a predetermined magnification. Therefore, the rectangular light flux having the predetermined size and position set by the blind 7 selectively illuminates the area on the reticle 10 having an arbitrary position and size. The light flux transmitted through the reticle 10 is projected by the projection lens 11 at a predetermined magnification to the substrate 1
2 is imaged.

A glass plate is used for the substrate 12,
It is placed on the stage 13. Positioning of the stage 13 is controlled based on a detection value of a laser interferometer system (not shown) whose position is monitored by a movable mirror 14.
Normally, it is not possible to perform exposure over the entire area of the substrate 12 in one exposure operation, so when one exposure is completed, the stage 13 is sent in the X or Y direction to expose another area,
By repeating this, the entire area of the substrate 12 is exposed.

By the way, in recent years, the device size required for liquid crystal devices has been increasing, and 10-inch class devices are also used in personal computers and the like. Moreover, the device size is expected to further expand in the future. A method of enlarging the effective area of the projection lens is conceivable in order to deal with these so-called giant devices, but it becomes more difficult to secure the depth of focus due to the size increase of the device and the limitation of the flatness on the substrate side. The reticle or photomask also has a large size, and it is difficult to make it defect-free due to the limit of flatness.

As a method of overcoming this drawback, there is a method of generating a device by using screen synthesis. This method is a method of exposing one liquid crystal device by using a plurality of reticle patterns formed on one or more reticles, and is already generally used in step-and-repeat projection exposure apparatuses for liquid crystals. There is. An exposure operation using this screen compositing method will be described with reference to FIGS. In this example, a pattern image 21 (indicated by diagonal lines) 4 is formed on the substrate 20.
A case will be described in which one pattern image is formed after the exposure is divided into two pattern regions 22, 23, 24, and 25, and all four shots are completed (FIG. 5).

In this exposure method, since the pattern image 21 to be formed on the substrate 20 is large and cannot be exposed by one shot, four reticles (reticles 26A and 26B, as shown in FIG. 6) are formed. 26C and 26D) are used. In each reticle, reticle patterns 27A and 27A corresponding to the pattern obtained by dividing the pattern image 21 into four are formed.
B, 27C and 27D are formed respectively, and the light-shielding band patterns 28A, 28B and 28C are formed around the boundaries thereof.
And 28D are formed.

These four reticle patterns 27A-2
The pattern image 21 is synthesized on the substrate 20 by exposing the 7D so that they are in contact with each other. First, as the first shot, the reticle pattern 27A formed on the reticle 26A is exposed on the substrate 20 to obtain a pattern image as shown in FIG. At this time, the blind 7 is set at the position shown in FIG. 8 with respect to the reticle 26A.

The blind 7 is composed of two hook-shaped blades 31 and 32, and these blades 31 and 32 are aligned on the light-shielding band pattern 28A formed on the reticle 26A. In this state, when the shutter (not shown) is opened for a certain period of time, a pattern image as shown in FIG. 7 can be formed on the substrate 20 as an exposure pattern by the first shutter.

As can be seen from this, the pattern image exposed on the substrate 20 does not expose the pattern in the area limited by the blind 7, but the inside of the light-shielding band formed on the reticle. The pattern of the area located at is exposed. Next, in order to expose the second pattern image to the right of the previously formed pattern image as the second shot, the reticle serving as the exposure original plate is changed from the reticle 26A to the reticle 26B, and at the same time the stage 13 is moved. It may be moved and similarly exposed.

At this time, the first and second shots are exposed by superimposing a small amount. This is a pattern exposed by the first shot and the second shot due to drawing error of the pattern formed on the reticle, distortion in the projection lens 11, positioning error of the stage 13, and the like. This is to prevent a break from occurring between the two.

[0014]

However, the following problems have occurred in the conventional system. First, in addition to the reticle drawing error, there is a step difference in the pattern due to the distortion of the lens and the positioning error of the stage 13. This can affect the electrical and physical properties of the device being manufactured. In particular, in devices such as liquid crystal displays, even micron-order steps affect the display characteristics of the device.

Secondly, when a liquid crystal device is exposed using a plurality of projection exposure apparatuses, an overlay error mainly changes due to lens distortion and changes stepwise at the connection portion of the exposure area. That is. This becomes a more serious problem in the case of a liquid crystal display. In particular, in the case of an active matrix type liquid crystal device, the contrast at the connection portion of the exposure region is different because it affects the operating characteristics of the thin film transistor. Even a slight difference in contrast is likely to be perceived by human visual characteristics, and therefore a difference in contrast results in deterioration of display quality.

The present invention has been made in consideration of the above points, and it is possible to perform exposure so that the difference in the contrast at the connecting portion of the exposure regions due to the screen composition is not perceived as much as the conventional method and the exposure method. Is to propose.

[0017]

In order to solve such a problem, according to the present invention, in a photomask having a pattern area in which a plurality of unit patterns are arranged substantially regularly, the plurality of unit patterns are formed in a peripheral portion of the pattern area. At least a part of the pattern area is discretely arranged, and the number of the pattern areas is reduced from the center toward the periphery.

First and second units having a plurality of unit patterns
An exposure method for forming a large-area pattern on the photosensitive substrate 12 by exposing the pattern regions of the first and second pattern regions so that the peripheral portions of the first and second pattern regions are continuous with each other on the photosensitive substrate 12. Of the first and second pattern areas, the photomasks are arranged such that the unit patterns in the peripheral portion 43 to be continuous are discrete and do not overlap, and the peripheral portions 43 are overlapped on the photosensitive substrate 12. To expose.

[0019]

By using a photomask in which the unit patterns in the peripheral portion 43 to be continuous in the first and second pattern areas are discrete and do not overlap, the peripheral portions 43 are overlapped on the photosensitive substrate. By exposing the first and second pattern areas to each other by exposure, the exposure amount of each unit pattern to be formed in the peripheral portion 43 should be continuous even when there is a difference in the exposure amount. The difference can be made hard to be perceived.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

Here, a step-and-repeat type projection exposure apparatus 10 is provided on a substrate 12 with a pattern image used for manufacturing a liquid crystal display for displaying an image by switching driving pixel electrodes arranged in a matrix by a thin film transistor. The case of performing exposure using will be described. In the case of this embodiment, the pattern image is divided into two left and right pattern images to be exposed, and one pattern image is formed after two shots are completed.

At this time, the exposure area 41 exposed by the first shot and the exposure area 42 exposed by the second shot on the substrate 12 are as shown in FIG. The portions corresponding to the connecting portions 43 overlap each other. When the connecting portion 43 of this screen is enlarged, it becomes as shown in FIG. Here, the square patterns shown by black and white represent each pixel of the liquid crystal display.

Of these, black-painted pixels represent pixels exposed by the first shot, and white pixels represent pixels exposed by the second shot. In the case of this embodiment, the area of nine pixels in the direction of connecting the exposure areas 41 and 42 corresponds to the connection portion 43.

Each of the plurality of pixels located in the connecting portion 43 is exposed only once by either one of the first shot and the second shot. It is designed not to be overexposed. Here, the reticle pattern (not shown) used for each shot is formed by chrome or the like so that the pixel portion that is exposed only by the other shot of the pixels arranged at the connecting portion 43 is not exposed. It is masked.

The number of pixels exposed by each shot among the pixels located at the connection portion 43 is reduced from the center of the shot toward the periphery, and the pixels are discretely arranged so that no regularity occurs. Has been done. Figure 1
In the case of (B), paying attention to a part of the pixels exposed by the first shot among the pixels located in the connection portion 43, the vertical plot of the pixels exposed by the first shot is shown. The number of directions is 9 in the order of the peripheral direction of the area (that is, from left to right), 8 ... 3 and 2
Irregular positions are selected and exposed so that the number decreases one by one.

On the other hand, the pixel exposed by the second shot in the connecting portion 43 corresponds to the pixel not selected by the first shot, and the number of pixels exposed at this time is the same. Once in the peripheral direction of the area (that is, in order from right to left) 9, 8, ... 3, 2,
The exposure is selected so that the number decreases by one.
In this way, the pixels located at the connection portion 43 are exposed so that the pixels exposed by the first shot and the pixels exposed by the second shot are gradually mixed with each other.

Accordingly, there is an electrical difference between the thin film transistor formed by the first shot and the thin film transistor formed by the second shot, which causes a difference in the operating characteristics of each pixel. Even if there is a slight contrast difference in the brightness of one pixel, the difference in brightness is mixed and it is difficult to perceive.

Further, among the areas exposed by the first or second shot, the areas closer to the center of the area from the peripheral portion are arranged so that more pixels are exposed by the same shot. The difference in contrast between the two shots appears to the human eye to be gradually changing. In particular, since the human eye is inferior in recognizing the pattern in which the contrast difference gradually changes, the connection part of the exposed liquid crystal display as in the example is hard to perceive and the entire screen is uniform. The display quality has improved.

On the other hand, in the case of the exposure by the conventional exposure method, as shown in FIG. 2A, the overlapping exposure area is not provided and the left half area 51 and the right half area 52 with respect to the center line L. Are exposed separately so that the first and second shots are connected to each other. Accordingly, FIG. 2B is an enlarged view of the connecting portion.
As described above, when there is a slight difference in contrast between the pixels formed by the first shot and the pixels exposed by the second shot, the difference is easily perceived, and It is perceived as if there is a line in the center of.

According to the above construction, a pattern image formed by arranging a plurality of pixel patterns in a matrix is divided into two left and right exposure areas 41 and 42, and each exposure area 4 is divided.
When dividing 1 and 43 into two shots and synthesizing screens, the connecting portion 43 of two exposure areas is overlapped and exposed,
In addition, the pixels formed by the two exposure areas may be formed to be mixed little by little by discretely selecting and exposing the pixels located in this area so as not to be exposed more than once. it can.

Thus, even if there is a difference in contrast between pixels exposed by each shot, it is possible to effectively avoid the possibility that the boundary portion between two exposure areas is perceived as a line. As a result, the brightness of the entire screen is perceived uniformly,
The display quality of the liquid crystal display can be further improved.

In the above-mentioned embodiment, the case where the liquid crystal display is divided into two exposure regions and divided into two shots for continuous exposure is described. However, the present invention is not limited to this, and one exposure pattern is used. Can be similarly applied to the case of connecting and exposing by using three or more shots. For example, it can be applied to a case where one exposure pattern is divided into four pattern images so as to be divided into two in the vertical direction and in the horizontal direction, and the pattern image is divided into four shots and joint exposure is performed. In this case, the pixels located in the central area of the screen, which are subjected to overlapping exposure for all four shots, are exposed in the same manner as described above so that the contrast difference is not noticeable.

Further, in the above-described embodiment, the case where the width of the exposure area which is exposed in the first and second shots is 9 pixels has been described, but the present invention is not limited to this. However, the width of the exposure area to be overlaid and exposed may be wider as the contrast difference between the respective shots is larger, and conversely, may be narrower as the contrast difference is smaller, and may be set according to the device design and process.

Further, in the above-described embodiment, among the pixels arranged in the overlapping exposure area, the number of pixels which are simultaneously exposed by the first shot or the second shot is 9 or 8. , 7 ... 2 and 1 are linearly reduced, but the present invention is not limited to this, and the number of exposed pixels becomes closer to the center of the area exposed by the other shot. It should be reduced.

Further, in the above-described embodiment, the arrangement of the pixels arranged in a direction perpendicular to the connecting direction (ie, the horizontal direction in the drawing) (ie, the vertical direction in the drawing) has no regularity. However, the present invention is not limited to this, and a pixel exposed by the first shot and a pixel exposed by the second shot within a range in which the contrast difference is not visually recognized. Need only be placed, and need not be placed so as not to have strict regularity.

Further, in the above-mentioned embodiment, the case where the pixels composing the liquid crystal display are arranged in a matrix has been described, but the present invention is not limited to this, and the pixels are formed in a small arrangement. It can be applied even if it is.

Further, in the above-mentioned embodiment, the case of exposing the field effect transistor driving each pixel constituting the liquid crystal display has been described, but the present invention is not limited to this, and other gates and wiring patterns are exposed. It can also be widely applied. For example, it can be applied to the case of forming a black matrix.

Further, in the above-mentioned embodiment, the case of exposing the pattern constituting the liquid crystal display has been described, but the present invention is not limited to this, and can be applied to the case of the plasma display.

Further, in the above-mentioned embodiment, the case where the exposure pattern is exposed by the step-and-repeat type projection exposure apparatus has been described, but the present invention is not limited to this, and the mirror projection type projection exposure apparatus and the like. The present invention can be widely applied to the case where one exposure pattern is obtained by screen composition by an exposure apparatus of another exposure method.

The plurality of pattern regions to be screen-synthesized on the substrate may be formed on the same reticle or may be divided on different reticles. Alternatively, one type of pattern area may be used, and the pattern area may be repeatedly exposed to form a pattern on the substrate (FIG. 3).

[0041]

As described above, according to the present invention, it is possible to expose the boundary portions, which are the connecting portions when the screens are combined, so as to overlap each other, and to arrange the unit patterns regularly arranged in this portion. By discretely selecting and exposing so as not to be repeatedly exposed more than once, even if there is a difference in the exposure amount of the unit pattern formed in the connection portion, it is possible to make it difficult to perceive the boundary portion between the two regions to be combined. .

[Brief description of drawings]

FIG. 1 is a schematic diagram used for explaining a connecting portion of a pattern exposed by an exposure apparatus according to the present invention.

FIG. 2 is a schematic diagram for explaining a connecting portion of a pattern exposed by a conventional method.

FIG. 3 is a schematic diagram for explaining another embodiment.

FIG. 4 is a schematic optical path diagram for explaining the configuration of a step type projection exposure apparatus.

FIG. 5 is a schematic plan view for explaining screen composition.

FIG. 6 is a schematic plan view for explaining a reticle used for the exposure.

FIG. 7 is a schematic plan view for explaining a process of generating an exposure pattern.

FIG. 8 is a schematic plan view for explaining a setting position of a blind with respect to a reticle.

[Explanation of symbols]

1 ... Exposure device, 2 ... Ultra high pressure mercury lamp, 3 ... Elliptical mirror, 4, 8 ... Reflection mirror, 5 ... Wavelength filter, 6 ...
… Fly-eye integrator, 7… blinds, 9…
... condenser lens, 10 ... reticle, 11 ... projection lens, 12, 20 ... substrate, 13 ... stage, 14
...... Movable mirror, 21 ...... Pattern image, 22, 23, 24,
25 ... Pattern area, 26A, 26B, 26C, 26
D ... Reticle, 27A, 27B, 27C, 27D ...
Reticle pattern, 28A, 28B, 28C, 28D ...
... Shading band pattern, 31, 32 ... Feather, 41, 42 ...
... exposure area, 43 ... connection part.

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location 7352-4M H01L 21/30 311 L

Claims (3)

[Claims] 1. A photomask having a pattern area in which a plurality of unit patterns are arranged substantially regularly, wherein the plurality of unit patterns are discretely present in at least a part of a peripheral portion of the pattern area, and at the center of the pattern area. The photo mask is arranged so that the number of the masks decreases from the periphery toward the peripheral portion. 2. The photomask has a second pattern region having a second peripheral portion corresponding to the peripheral portion, and the positions of the unit patterns existing in the peripheral portion and the second peripheral portion are: The unit pattern and the second pattern which are present in the peripheral portion when the peripheral portion and the second peripheral portion are overlapped with each other.
The photomask according to claim 1, wherein the photomask is arranged so as not to overlap with the unit patterns existing in the peripheral portion of the photomask. 3. First and second units having a plurality of unit patterns
An exposure method for forming a large-area pattern on the photosensitive substrate by exposing the pattern region of 1) so that the peripheral portions of the first and second pattern regions are continuous with each other on the photosensitive substrate, Using the photomask in which the unit patterns in the peripheral portion to be continuous of the first and second pattern regions are discrete and are arranged at positions that do not overlap, the peripheral portions are overlapped on the photosensitive substrate. An exposure method characterized by exposing to light.