JP2002122979A - Method for manufacturing photo mask, photo mask, reflecting plate, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo mask permitting manufacture of a favorable liquid crystal display device by suppressing generation of striped irregularity accompanied by seams of scanning and variation in an exposure dose of light for scanning, and to provide a manufacturing method therefor. SOLUTION: Scanning is performed not in sequential order in the scanning direction, but performed in back-and-forth order. Namely, the scanning is performed in such order as after a scan width W1 is scanned, a scan width W3 is scanned with a scan width W2 skipped, and then a scan width W2 is scanned by coming back one section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used in a photolithography process for manufacturing a substrate of a liquid crystal display device and a semiconductor device, a method of manufacturing the same, a reflector and a liquid crystal display device manufactured by using the photomask. Things.

[0002]

2. Description of the Related Art In the production of liquid crystal display elements and semiconductor elements,
As a method for performing fine processing of a thin film, a photolithography method is used. This involves applying a photoresist on a substrate, using a photomask, exposing light to only predetermined locations on the substrate, and developing the photoresist, leaving the photoresist only at predetermined locations and exposing the others. .
The exposed portion can be processed by a method such as etching. As described above, a photomask is indispensable for photolithography, and the processing accuracy of photolithography depends on the accuracy of the photomask. When there is an inconvenient defect or pattern on the photomask, the defect or pattern is transferred by exposure. If such a defect or pattern is present on a photomask used for manufacturing a display device such as a liquid crystal display element, the pattern will be visible at the time of display, and the transferred product will be defective. In particular, when the shape of the reflector in a reflective liquid crystal display element is formed using a photomask, the reflection characteristics of the reflector change depending on the defect or pattern of the photomask. As a result, defects and patterns are remarkably seen. Therefore, it is necessary to remove defects on the photomask.

On the other hand, in the production of liquid crystal display elements and semiconductor elements, there is a problem of cost reduction due to reduction of photo processes. The number of photo steps can be reduced by a single exposure such as a halftone mask in which a part of the light-shielding film has transparency or a gray-tone mask in which a part of the light-shielding film is formed with a pattern below the resolution limit of the exposure device. A photomask capable of partially irradiating different exposure amounts is used. Thus, a photoresist film can be formed at two or more steps and a plurality of depths, and two photo processes can be performed once. (C.
W. Kim et al .: A Novel Four-Mask
-Count Process Architect
re for TFT-LCDs, SID00DIGE
ST pp 1006-1009).

In the case of using a gray-tone mask, it is necessary to densely form a fine mask pattern having a resolution equal to or less than the resolution limit of an exposure apparatus, and a fine processing accuracy is required.
Further, when a gray-tone or half-tone mask is used, unevenness due to a minute difference in the exposure amount is likely to appear. For this reason, it is necessary to suppress the cause of very slight unevenness of the photomask.

A method for manufacturing a photomask is generally such that a metal thin film (such as chrome) is formed on a substrate (such as quartz) that transmits ultraviolet light.
Is formed and patterned. In patterning, a photoresist is applied to a substrate on which a light-shielding film for shielding light, such as a metal thin film, is formed, exposed and developed by a drawing machine, and then the light-shielding film is etched. Thus, a photomask in which the light-shielding film is patterned into a predetermined shape can be manufactured.

[0006] In the exposure process of photomask production, generally, a drawing for designating a predetermined location is drawn by CAD (computer aided design), and the data of the drawing is transferred to an exposure facility called a drawing machine. The drawing machine exposes only a predetermined portion according to the data of the design drawing. The design drawing shows the light transmitting portion and the light shielding portion on the photomask in a two-dimensional plane on the substrate. The drawing machine performs drawing by scanning a light transmitting portion (or a light blocking portion) on a substrate with light having a very small diameter according to a design drawing, and exposes a photoresist to a predetermined shape.

FIG. 7 shows a drawing method by a drawing machine. As shown in FIG. 7A, a single scanning can move a distance of several tens μm to several hundreds μm on the substrate, and the scanning is sequentially performed at this distance. After scanning a distance of several tens μm to several hundreds μm on the substrate, scanning a distance of several tens μm to several hundreds μm from the subsequent portion is repeated. Hereinafter, the scanning band of several tens μm to several hundred μm is referred to as “scanning width”. The scanning of one scanning width is sequentially performed on the substrate, and the scanning of the next stage is repeated, so that the entire plane on the substrate is drawn. For this reason, drawing is performed in order for each fixed scanning width.

[0008]

Here, if the positional accuracy of the end position and the start position of the scan is poor at the joint between one scan width and the next scan width, as shown in FIG. , Scanning may be performed in an overlapped manner, or a portion where scanning is not performed may occur. When the scanning is overlapped, the exposure amount is increased only in that portion, so that the width of the exposed portion on the substrate is slightly increased as compared with other exposed portions. If scanning is not performed,
The width of the exposed portion on the substrate is slightly smaller than the other exposed portions.

When a striped scan having a fixed scan width is performed,
At the seam of the scanning width, a very large or small exposed portion becomes a stripe, and the stripe can be visually confirmed. When such stripes can be visually inspected on a photomask, when a liquid crystal display element or the like is manufactured based on this, the stripes appear on the liquid crystal display element as they are,
There is a problem that the unevenness appears as stripe-like unevenness and becomes a defective product as a reflection plate or a liquid crystal display element.

Further, even when the irradiation amount of the scanning light slightly changes due to the fluctuation of the light source or the fluctuation of the optical system, the exposure amount changes between one scanning width and the next scanning width, and the portion to be exposed is changed. Have a slightly different width and become stripes, so that the stripes can be visually confirmed. Such stripes also appear as stripe-like unevenness on the liquid crystal display element, and also cause a problem that the liquid crystal display element becomes a defective product.

The present invention has been made to solve the above problems, and
It is an object of the present invention to provide a photomask capable of manufacturing a good liquid crystal display element by suppressing the occurrence of stripe-like unevenness due to a change in a seam of scanning or an irradiation amount of scanning light, and a method for manufacturing the same.

[0012]

In order to solve the above-mentioned problems, a method of manufacturing a photomask according to the present invention comprises the steps of: scanning a surface of a substrate with light to draw a predetermined pattern; A plurality of scans performed for each distance are performed in an order before and after the scan direction.

The method of manufacturing a photomask according to the present invention includes a step of drawing a predetermined pattern by scanning light on the substrate surface, and performing the scanning on the substrate surface in a direction perpendicular to the scanning direction. Are performed in the order of before and after.

According to this method, when the light intensity of the exposure device changes, a portion where the light is strong and a portion where the light is weak can be mixed in the substrate surface, and the stripe-like unevenness can be suppressed.

The method of manufacturing a photomask according to the present invention is characterized in that the order of scanning is irregular.

According to this method, the intensity of light can be mixed in the plane of the substrate to suppress stripe-like unevenness.

Further, the method of manufacturing a photomask of the present invention includes a step of drawing a predetermined pattern by scanning light on a substrate surface, and a starting point of each scanning is arranged so as to be shifted in a scanning direction. It is characterized by having.

Further, the method for manufacturing a photomask according to the present invention is characterized in that the starting points of scanning are arranged irregularly in the plane of the substrate.

According to this method, it is possible to prevent the scanning start points of the photomask from being lined up in a row, and to suppress the occurrence of stripe-like unevenness.

The method of manufacturing a photomask according to the present invention is characterized in that the lengths of adjacent scans in the direction perpendicular to the scan direction are different.

According to this method, the arrangement of the scanning start points can be made more irregular, and stripe-like unevenness can be suppressed.

The method of manufacturing a photomask of the present invention includes a step of drawing a predetermined pattern by scanning light on a substrate surface, and performing drawing at the same location on the substrate surface two or more times. The scanning start points for drawing the same portion are different from each other.

According to this method, it is possible to suppress the difference in the exposure amount at the seam of scanning and to suppress the occurrence of stripe-like unevenness.

Further, a photomask of the present invention is manufactured by the above-described method for manufacturing a photomask.

With this configuration, it is possible to provide a photomask in which stripe-like unevenness is suppressed.

Further, the photomask of the present invention is manufactured by the above-described method for manufacturing a photomask, and the width of the drawn pattern is equal to or less than the resolution limit of an exposure machine using the photomask. And

According to this configuration, in a configuration in which the pattern width is equal to or less than the resolution limit of an exposing machine using a photomask, stripe-like unevenness can be suppressed.

Further, in the method of manufacturing a liquid crystal display device according to the present invention, a photoresist previously coated on the device is exposed and developed by using the above-described photomask, so that a plurality of two or more steps of photoresist are formed. It is characterized by including a step of increasing the thickness.

According to this method, the number of photo steps can be reduced,
A liquid crystal display device can be provided at low cost.

Further, the reflector of the present invention is manufactured by a manufacturing method including an exposure step using the above-described photomask.

With this configuration, it is possible to provide a reflection plate in which stripe-like unevenness is suppressed.

Further, the liquid crystal display element of the present invention is characterized in that it is manufactured by a manufacturing method including an exposure step using the above-described photomask.

With this configuration, it is possible to provide a liquid crystal display element in which stripe-like unevenness is suppressed.

[0034]

(Embodiment 1) An example of an embodiment of the present invention will be described with reference to the drawings. FIG.
1 illustrates a method for manufacturing a photomask according to a first embodiment of the present invention, particularly a drawing method using a drawing machine. FIG. 2 shows a cross section of the photomask in the photomask manufacturing method according to the embodiment of the present invention.

Referring to FIG. 2, a photomask has a light-shielding film 2 made of a chromium thin film or the like formed on a substrate 1 that transmits an exposure wavelength of an exposure device used for photolithography. And As shown in FIG. 2A, a photoresist 3 is formed on the light shielding film 2.
Is applied. The drawing machine irradiates light including the photosensitive wavelength of the photoresist 3 with a fine diameter on the photomask surface, and scans the light on the photomask. At this time, by performing irradiation and non-irradiation of light based on a mask design drawing prepared in advance, drawing is performed to expose only a photoresist of a predetermined pattern shown in the design drawing. It is desirable that the diameter of the irradiated light be smaller than the precision of the pattern formed on the photomask.

On the substrate 1, a predetermined portion of the photoresist 3 ′ was exposed as shown in FIG. 2B by drawing by scanning with light. Thereafter, as shown in FIG. 3C, the photoresist was developed with a photoresist developer to remove the photoresist 3 ′. Next, the exposed light-shielding film is etched and the photoresist is stripped to complete a photomask as shown in FIG.

The drawing method of the photomask manufacturing method according to the first embodiment will be described. In FIG. 1, scanning is indicated by a solid line with an arrow, and the order of scanning is indicated by a broken line with an arrow. That is, scanning is started at A1 in FIG. 1 and scanning is performed up to A2. Next, scanning is started at B1 for the area adjacent to A1 and A2, and scanning is performed up to B2. Next, the process of scanning C2 from C1 adjacent thereto is repeated. In this way, the drawing of the scanning width W1 is performed. Next, scanning is started from a point A5 different from the end point of the previous scanning, scanning is performed to A6, and then scanning is performed from B5 to B6 adjacent to A5 to A6, and the scanning width of the scanning width W3 is reduced. draw. Next, an area having a scanning width W2 between the scanning widths W1 and W3 is scanned.

As described above, the scanning is not performed sequentially in the scanning direction, but is performed in the preceding and following order.

Since the pattern formation of the photomask is performed by irradiating light with a drawing machine, if the irradiating light has a high or low intensity, the pattern size may slightly change. That is, when the light is strong, the exposure amount increases, and the width of the photosensitive region of the photoresist increases. The opposite is true when the light is weak. The intensity of the light slightly fluctuates with time depending on the ambient temperature of the light source, the time since power-on, the total lighting time, and the like. If the positioning accuracy of the scanning is not accurate, the end position and the start position are shifted as shown in FIG. 7B at the joint between a certain scan and the next scan, so that the scans are performed at the same time. May not be performed. When the scanning is overlapped, the exposure amount is increased only in that portion. Therefore, the width of the exposed portion on the substrate is slightly increased as compared with other exposed portions. In addition, a portion where scanning is not performed occurs, and the width of the portion to be exposed on the substrate is reduced, although it is very small as compared with other exposed portions.

When the pattern size changes alone or when they are uniformly distributed over the entire area, they cannot be visually confirmed and pose no problem. However, when they exist regularly, they appear as stripe-like unevenness, and the stripes can be visually confirmed. When manufacturing a liquid crystal display device or the like based on a photomask in which such stripes can be seen,
The stripes appear as they are on the liquid crystal display element and appear as stripe-like unevenness, which causes a problem that the liquid crystal display element becomes a defective product.

When the scanning sequence is performed in order, slight variations in pattern size appear in the scanning order as they are, so that stripe-like unevenness is strongly seen and emphasized.

Therefore, in the first embodiment, the order of scanning is set to be earlier or later than the scanning direction. By doing so, when the intensity of the irradiated light changes with time,
Since a place where light is strong and a place where light is weak can be mixed in the photomask plane, the size of the pattern is uniformly dispersed in the mask plane, and the appearance of stripe-like unevenness can be suppressed.

In the first embodiment, as shown in FIG. 1, after scanning with the scanning width W1, after scanning with the skipped width W3,
The order of scanning back to W2 is one, but the order of scanning is not limited to this, and it is better to make the order as irregular as possible in the mask plane. Can be suppressed, which is desirable. Further, in the first embodiment, the scanning is performed in the direction perpendicular to the scanning direction so as to be adjacent to each other. However, as shown in FIG. 3, the scanning is performed in the order perpendicular to the scanning direction on the substrate surface. May be used for scanning. In this case, the slight size of the pattern caused by the change in the intensity of the light is uniformly dispersed in the mask surface, and the stripe-like unevenness can be suppressed. In addition, the variation in the positioning accuracy of the scanning start position is also made uniform in the photomask plane, so that striped unevenness can be suppressed.

Embodiment 2 A method for manufacturing a photomask according to Embodiment 2 will be described with reference to FIG. The method for manufacturing a photomask according to the second embodiment is described in the first embodiment.
Only the light scanning method by the drawing machine is different, and the other points are the same. Therefore, FIG. 4 shows the difference between the scanning methods, and only the different parts will be described below.

FIG. 4 shows that the scanning start points A adjacent to each other in a direction perpendicular to the scanning direction are shifted in the scanning direction and are arranged in a dispersed manner on the photomask surface. is there. By doing so, even if the pattern size changes slightly due to the intensity of the scanning light or the scanning positioning accuracy, the change is dispersed in the photomask surface, so that the stripe-shaped unevenness occurs. The visibility can be suppressed. By arranging the scanning start points irregularly, a good photomask can be manufactured without being seen as unevenness.

As shown in FIG. 5, the lengths W of adjacent scans may be different (W4 to W6 in FIG. 5).
When the length W is changed at random, as shown in FIG. 5, since the scanning start point A or the end point is hardly regularly arranged, even if there is a slight change in the pattern size, the unevenness can be obtained. Can be suppressed. Further, similarly to the first embodiment, it is not necessary to sequentially scan adjacent scanning lines, and the order of scanning may be reversed.

(Embodiment 3) A method of manufacturing a photomask of Embodiment 3 will be described. The photomask manufacturing method according to the third embodiment also includes only the light irradiation method according to the first and second embodiments.
Otherwise, they are equivalent. Therefore, only different parts will be described with reference to FIG. FIG. 6 shows a light scanning method by the drawing machine according to the third embodiment. In the third embodiment, the same location on the photomask surface is scanned two or more times by scanning with different starting points and ending points. At this time, the irradiation amount of the scanning light is adjusted so that a predetermined exposure amount can be obtained by a plurality of scans. For example, in the case of performing two scans, the irradiation amount for one time is set to one half of the normal irradiation amount, and in the case of performing three scans, it is set to one third. As in the third embodiment, by setting the start points of scanning for drawing the same portion to be different from each other, light irradiation by another scan is performed at a joint between the scans. The change in the pattern size is smaller than at the seam due to, and striped unevenness can be suppressed.

In the third embodiment, as in the first embodiment, by reversing the scanning order,
The occurrence of unevenness can be further suppressed. Further, similarly to the second embodiment, by dispersing and arranging the scanning start positions in the photomask surface, it is possible to suppress the occurrence of unevenness.

In the photomask manufactured by using the photomask manufacturing method of the present invention, it is possible to suppress the appearance of stripe-like unevenness. In particular, when forming a gray-tone mask in which the pattern width formed by the light-shielding film is equal to or less than the resolution limit of an exposure machine using the photomask,
Exposure of the photoresist coated in advance on the device,
By developing, the method can include a step of forming the photoresist to have a plurality of thicknesses of two or more steps, thereby providing a method of manufacturing a liquid crystal display element in which the number of photo steps is reduced, and a favorable liquid crystal in which unevenness is suppressed. A display element can be provided.

Further, the reflector manufactured by the manufacturing method including the exposure step using the photomask of the present invention can provide a good reflector in which stripe-like unevenness is suppressed. Such a reflector can be used as an external scattering reflector of a display device such as a liquid crystal display device.

As described above, in the liquid crystal display device manufactured by the manufacturing method including the exposure step using the photomask of the present invention, both the transmissive liquid crystal display device and the reflective liquid crystal display device generate stripe-like unevenness. Is suppressed, and good display can be performed.

[0052]

As described above, according to the method for manufacturing a photomask of the present invention, the photomask looks striped due to a change in the irradiation amount of light from the drawing machine and an inaccurate positioning accuracy when the photomask is formed. Unevenness can be suppressed. The liquid crystal display device manufactured by using the mask manufactured by this manufacturing method,
The occurrence of unevenness due to stripe-like unevenness on the photomask can be suppressed, and the occurrence of defects in the liquid crystal display element can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method of scanning a drawing machine in a method for manufacturing a photomask according to a first embodiment.

FIG. 2 is a cross-sectional view of the mask at the time of drawing in the photomask manufacturing method according to the first embodiment;

FIG. 3 is a diagram showing another scanning method of the drawing machine in the photomask manufacturing method according to the first embodiment;

FIG. 4 is a view showing a method of scanning a drawing machine in a method for manufacturing a photomask according to a second embodiment.

FIG. 5 is a diagram showing another scanning method of the drawing machine in the photomask manufacturing method according to the second embodiment.

FIG. 6 is a diagram showing a method of scanning a drawing machine in a method for manufacturing a photomask according to a third embodiment.

FIG. 7 is a diagram showing a scanning method of a drawing machine in a conventional photomask manufacturing method.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 light-shielding film 3 photoresist 4 light source W scanning width A scanning start point

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H091 FA16Z FA34Y FC10 FC23 LA12 LA16 2H095 BB01 BB07 BB33 BB35 2H097 AA03 AA11 BB01 JA02 LA10 LA11 LA17

Claims (12)

[Claims] In a step of drawing a predetermined pattern by scanning light on a substrate surface, a plurality of scans performed at predetermined distances in the scanning direction are performed in the order before and after the scanning direction. A method for manufacturing a photomask, comprising: 2. The method according to claim 1, further comprising the step of scanning the substrate surface with light to draw a predetermined pattern, wherein the scanning is performed in the order perpendicular to the scanning direction on the substrate surface. A method for manufacturing a photomask, which is characterized 3. The method according to claim 1, wherein the order of the scanning is irregular. 4. A photomask according to claim 1, further comprising a step of drawing a predetermined pattern by scanning light on the surface of the substrate, wherein a starting point of each scan is shifted in a scanning direction. Production method. 5. The method according to claim 4, wherein the starting points of the scanning are arranged irregularly in the plane of the substrate. 6. The method of manufacturing a photomask according to claim 4, wherein the lengths of scans adjacent to each other in a direction perpendicular to the scan direction are different. 7. A scanning method for performing drawing of a predetermined pattern by scanning light on a substrate surface, performing drawing twice or more at the same location on the substrate surface, and performing drawing at the same location on the substrate surface. A method for manufacturing a photomask, wherein starting points are different from each other. 8. A photomask manufactured by the method for manufacturing a photomask according to any one of claims 1, 2, 4, and 7. 9. The photomask according to claim 1, wherein a width of the drawn pattern is equal to or less than a resolution limit of an exposure machine using the photomask. 10. A step of exposing and developing a photoresist previously coated on an element using the photomask according to claim 9 so that said photoresist has a plurality of thicknesses of two or more steps. A method for manufacturing a liquid crystal display element, comprising: 11. A reflector manufactured by a manufacturing method including an exposure step using the photomask according to claim 8. 12. A liquid crystal display device manufactured by a manufacturing method including an exposure step using the photomask according to claim 8.