JP2002268200A - Photomask for gray tone exposure and method for applying photosensitive resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the first problem that the taper angle of an ordinary film thickness part becomes smaller near gray tone exposure and the second problem that it is difficult to make gray tone film thickness uniform. SOLUTION: In order to solve the first problem, the interval between patterns for gray tone exposure is made narrower at the center and wider at the peripheries. In order to solver the second problem, photosensitive resins different from each other in optical sensitivity are applied two or more times and an exposure reaction is accelerated only in the upper photosensitive resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a gray-tone photomask for changing the transmittance of ultraviolet light in a stepwise manner, and a photosensitive resin film in a single exposure using the gray-tone photomask. The present invention relates to a patterning method for forming a plurality of thicknesses.

[0002]

2. Description of the Related Art In recent years, an exposure method called gray-tone exposure has been put to practical use. In the conventional exposure method, a film to be processed under the photosensitive resin is patterned depending on the presence or absence of the photosensitive resin in either a portion where the photosensitive resin is left or a portion where the photosensitive resin is removed. On the other hand, in the case of gray-tone exposure, after forming a multi-layer film to be processed, in addition to the part where the conventional photosensitive resin is left and the part where the conventional photosensitive resin is removed in a single exposure, the thickness of the remaining part is reduced. , Patterning a multi-layer work film at once,
This is to reduce the number of exposures. Here, a patterning method using a gray-tone photomask is performed in the following steps.

Application: A photosensitive resin is applied.

Prebaking: The solvent of the applied photosensitive resin is heated and removed.

Exposure: Exposure is performed using a gray-tone photomask.

Development and rinsing: development and washing are performed.

Post bake: Heat and remove the developer and cleaning solution remaining in the photosensitive resin.

As a result, a portion where the applied thickness of the photosensitive resin is almost left, a portion where the applied thickness is completely removed, and a portion where the thickness of the photosensitive resin is in between are formed. The portion of the photomask having an intermediate film thickness is usually formed of a pattern having a resolution equal to or less than the resolution of the exposure apparatus used, and the transmitted ultraviolet light is reduced and made uniform.

[0009]

However, when the gray-tone exposure is performed, there is a problem that the taper angle of the photosensitive resin portion having a normal film thickness is different depending on whether it is near the gray-tone exposed portion or not. In FIG. 6, reference numeral 1 denotes a normal film thickness portion;
Denotes a gray-tone film thickness portion, and an end face of the normal film thickness portion 1 facing the gray-tone film thickness portion 2 has a taper angle α as shown in the AA cross section, and a normal film thickness not facing the gray-tone film thickness portion. The end face of the portion has a taper angle β as shown in the BB section, and β
> Α. For example, when a pattern obtained by repeating a light-shielding portion and a non-light-shielding portion having a resolution of 3 μm and a width of 2 μm on an exposure machine is exposed using a positive photosensitive resin OFPR-5000 (manufactured by Tokyo Ohka), α = 60 degrees and β = 40 degrees. . This is because the influence of diffraction extends to the normal exposure portion in the vicinity of the gray tone exposure portion, and the photosensitive resin taper angle is reduced. If the taper angles are different, the amount of dimensional shift during etching changes, and the finished shape will not be as designed. Further, there is a problem that the thickness of the photosensitive resin in the gray tone portion varies within the substrate surface. Taking a positive photosensitive resin as an example, when the photosensitive resin is irradiated with sufficient ultraviolet light, a soluble group is formed and becomes alkali-soluble and dissolves. Is insufficient, so that a soluble group is partially formed or cannot be formed, resulting in poor uniformity of the photosensitive resin film thickness after development. As a matter of course, if the photosensitive resin film thickness is not uniform, the processing accuracy deteriorates. SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a photomask and a manufacturing process for uniformly forming a finished shape of a normal exposure portion including a graytone exposure portion and a film thickness of the graytone exposure portion.

[0010]

In order to achieve the purpose of uniformly forming the finished shape of the normal exposure section including the above-mentioned gray-tone exposure section, first, a resolution of an exposure machine for patterning a photosensitive resin is used. In the step of repeatedly forming a light-shielding portion and a non-light-shielding portion formed in the following dimensions and forming a plurality of photosensitive resin film thicknesses, a film of a normal photosensitive resin is formed in a portion where the light-shielding portion and the non-light-shielding portion are repeated. A portion close to the portion where the thickness is to be formed is to be a photomask for gray-tone exposure in which the width of the light-shielding portion and the non-light-shielding portion is made wider than that of the portion far from the second portion. Second, a normal photosensitive resin film thickness is formed. The ratio of the non-light-shielding portion width to the light-shielding portion width of the portion close to the portion and the far portion is the same as that of the gray-tone exposure photomask, and thirdly, the normal photosensitivity using a positive photosensitive resin. Shape resin film thickness In a portion other than a portion adjacent to a portion where the light-shielding portion and the non-light-shielding portion are repeated, a non-light-shielding portion having a dimension width smaller than or equal to the resolution of the exposure machine is provided, and a light-shielding portion having the dimension width is provided. Fourth, the dimensions of the portion forming the normal photosensitive resin film thickness facing the portion where the light-shielding portion and the non-light-shielding portion are repeated face the portion where the light-shielding portion and the non-light-shielding portion are repeated. The photomask for gray-tone exposure to be larger than the non-light-shielded portion, and the range to be further enlarged is a portion where at least the light-shielding portion and the non-light-shielding portion in contact with the portion where the normal photosensitive resin film thickness is formed are repeated. The length is a gray-tone exposure photomask provided adjacent to a portion where the light-shielding portion and the non-light-shielding portion are repeated. Also, in order to achieve the purpose of making the gray-tone exposed portion film thickness uniform,
First, after a photosensitive resin is applied to the substrate on which the film to be processed is formed, a photosensitive resin having better optical sensitivity than the photosensitive resin is further applied to the substrate surface on which the photosensitive resin is applied. Secondly, before applying a photosensitive resin having better optical sensitivity than the photosensitive resin, a solvent for the photosensitive resin having good optical sensitivity is applied.

[0011]

(Embodiment 1) Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a pattern of a photomask for gray-tone exposure according to an embodiment of the present invention. In FIG. 1, a light-shielding portion 3 and a non-light-shielding portion 4 having a dimension width smaller than the resolution of an exposure machine to be used are repeatedly formed in order to form a gray-tone film thickness portion 2 having a thickness smaller than the normal film thickness portion 1 of the photosensitive resin. It is a thing. The exposure machine used here has a resolution of 3 μm and a light-shielding portion 3 near the center of the gray-tone film thickness portion 2.
And the width l of the non-light-shielding portion 4 is set to 1 μm, and the width is increased by 0.5 μm toward the periphery (normally, the film thickness portion 1).
The width L = 2.5 μm in the portion closest to the normal film thickness portion 1. On a glass substrate, a Ti film was formed to a thickness of 2000 mm, and a positive photosensitive resin OFPR-5000 was applied at a thickness of 1.2 μm.
After exposure and development, a SEM photograph was taken and the taper angle of the AA section was measured to be 55 degrees.

Here, it is preferable that the area ratio between the adjacent light-shielding portions 3 and the non-light-shielding portions 4 be constant irrespective of the center and the periphery of the gray-tone film thickness portion. If the area ratio varies depending on the place, the gray-tone film thickness changes and the flatness is impaired. Therefore, regardless of the distance to the normal film thickness part 1, the light shielding part 3 and the non-light shielding part 4
It is essential that the width ratios be the same.

(Embodiment 2) FIG. 2 is a view for explaining a pattern of a gray-tone exposure photomask according to another embodiment of the present invention. In FIG. 2, a non-light-shielding portion 4 having a resolution equal to or less than the exposure machine resolution is provided around the normal film thickness portion 1, and the light-shielding portion 3 is patterned around its periphery. In this embodiment, a non-light-shielding portion having a width of 1 μm and a light-shielding portion having a width of 1 μm are provided. As a result, the taper angle of the peripheral edge of the normal film thickness portion 1 became almost the same including the portion adjacent to the gray tone film thickness portion 2.

(Embodiment 3) FIG. 3 is a view for explaining a pattern of a gray-tone exposure photomask which is still another embodiment of the present invention. FIG. 3 shows the gray tone film thickness part 2
The design dimension of the normal film thickness portion 1 in the peripheral portion of FIG. Although the conventional design dimension 5 is shown by a solid line, the taper angle of the normal thickness section 1 becomes smaller around the gray-tone film section 2, so that the dimension shift amount after the etching process becomes larger and smaller than the design dimension. Become. Therefore, it is usually necessary to increase the design dimension within a range in which the taper angle of the film thickness portion 1 becomes small, and the design dimension 6 is indicated by a broken line.

When the length of the gray-tone film thickness portion 2 adjacent to the normal film thickness portion 1 is m, the influence of the gray-tone exposure affects at least the normal film thickness portion 1 in the region of the adjacent length m. Therefore, the design size is increased in this range.

(Embodiment 4) FIG. 4 shows a method of coating a photosensitive resin according to an embodiment of the present invention a plurality of times to make the gray-tone exposure film thickness uniform. FIG. 4A shows that the film to be processed 1 is made of 3000 ° SiN, and the film to be processed 2 is
As a first photosensitive resin film 8, a positive photosensitive resin (optical sensitivity: 80 mJ /
cm2) with a spin coater at 6000 °. FIG. 4B shows a positive photosensitive resin (optical sensitivity 40) as a second photosensitive resin film 9 on the first photosensitive resin film 8.
mJ / cm 2) with a spin coater at 6000 °. FIG. 4C shows the cross-sectional shape of the photosensitive resin after exposure and development using the gray-tone photomask 10. The uniformity of the thickness of the photosensitive resin film corresponding to the gray-tone portion 11 was improved by adjusting the exposure amount to be exactly the thickness of the first photosensitive resin film 8. This is because when the non-light-shielding portion 12 is irradiated with sufficient ultraviolet light, the ultraviolet light reaches the lowermost portion of the first photosensitive resin film 8 and an alkali-soluble group is generated.
All the photosensitive resin films are removed. However, since the amount of light is attenuated due to the effect of diffracted light in the gray tone portion 11, the light does not reach the first photosensitive resin film. In particular, when the optical sensitivity of the second photosensitive resin film is better than the optical sensitivity of the first photosensitive resin film, a distinct difference occurs in the generation of alkali-soluble groups. Therefore, only the first photosensitive resin film remains, and the gray tone film thickness becomes uniform.

However, if the photosensitive resin is directly applied a plurality of times, there is a problem of wettability, and it is difficult to apply the second photosensitive resin film. FIG. 5 shows a method for improving wettability.
Optical sensitivity 80mJ on glass substrate with N, a-Si film
/ Cm 2 of a first photosensitive resin film. Next, a solvent for a second photosensitive resin film having an optical sensitivity of 40 mJ / cm 2 is applied, and then a second photosensitive resin film is applied. Next, perform pre-bake, gray tone exposure, development, and rinsing,
A uniform gray tone film thickness is created.

[0018]

As described above, according to the present invention, the normal film thickness portion in the gray tone exposure can also be made uniform by devising the gray tone portion pattern or the peripheral pattern of the normal film thickness portion. Further, by using photosensitive resins having different optical sensitivities in combination, a clear difference in the thickness of the photosensitive resin can be produced by graytone exposure, and a uniform graytone film thickness can be obtained. As a result, stable processing can be realized and the number of photomasks can be reduced, which contributes to a reduction in process cost and is extremely useful industrially.
If the present invention is used, the effect of resource saving such as reduction of a photomask and the development of a liquid crystal product as an energy-saving device are useful, so that the present invention is friendly to the global environment and space environment.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pattern for realizing gray-tone exposure according to an embodiment of the present invention.

FIG. 2 is a diagram showing a pattern for realizing gray-tone exposure according to another embodiment of the present invention;

FIG. 3 is a diagram showing a pattern for realizing graytone exposure according to another embodiment of the present invention.

FIG. 4 is a diagram showing an embodiment of the present invention for making the gray-tone film thickness uniform.

FIG. 5 is a diagram showing a flow of another embodiment of the present invention for making the gray-tone film thickness uniform.

FIG. 6 is a diagram showing a pattern for realizing a conventional gray-tone exposure.

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 1 Normal film thickness part 2 Gray tone film thickness part 3 Light shielding part 4 Non-light shielding part 5 Conventional design dimension 6 Design dimension 8 First photosensitive resin film 9 Second photosensitive resin film

Claims (7)

[Claims] When a photosensitive resin is patterned by ultraviolet light, a light-shielding portion and a non-light-shielding portion which are formed with dimensions smaller than the resolution of an exposing machine for patterning the photosensitive resin are repeatedly formed. In the step of forming a plurality of resin film thicknesses, in the portion where the light-shielding portion and the non-light-shielding portion are repeated, a portion close to a portion where a normal photosensitive resin film thickness is formed is compared with a far portion, and the light-shielding portion and the non-light-shielding portion are compared. A photomask for gray-tone exposure characterized by having a wide width. 2. The photo for gray-tone exposure according to claim 1, wherein the ratio of the width of the non-light-shielding portion to the width of the light-shielding portion is the same between a portion near the portion where the film thickness of the ordinary photosensitive resin is formed and a portion far from the portion. mask. 3. A portion of the normal photosensitive resin using a positive photosensitive resin, which is formed with a film thickness of an exposure machine, except for a portion adjacent to a portion where the light-shielding portion and the non-light-shielding portion are repeated. A gray-tone exposure photomask provided with a non-light-shielding portion having a dimension width equal to or less than the resolution and a light-shielding portion having the dimension width. 4. The size of a portion forming a normal photosensitive resin film thickness facing a portion where the light-shielding portion and the non-light-shielding portion are repeated is compared with a portion not facing the portion where the light-shielding portion and the non-light-shielding portion are repeated. Photomask for gray-tone exposure to enlarge. 5. A range in which the light-shielding portion and the non-light-shielding portion which are in contact with a portion where a normal photosensitive resin film thickness is formed is repeated at least. 5. The photomask for gray-tone exposure according to claim 4, wherein the photomask is provided adjacent to the substrate. 6. When patterning a photosensitive resin by ultraviolet light, a photosensitive resin is applied to a substrate on which a film to be processed is formed, and then the photosensitive resin is applied to the surface of the substrate on which the photosensitive resin is applied. A method for applying a photosensitive resin, comprising applying a photosensitive resin having better optical sensitivity than a photosensitive resin. 7. The photosensitive resin according to claim 6, wherein a solvent of the photosensitive resin having good optical sensitivity is applied before the photosensitive resin having good optical sensitivity is applied to the substrate surface. Coating method.