JPH0562894A - Forming method for fine pattern - Google Patents

Abstract

PURPOSE:To prevent deterioration of a resist pattern due to the deviation of focusing at the time of patterning exposure by bringing photoresist into contact with alkaline solution in a short time to remove resin on the surface of the photoresist, performing the patterning exposure, and then developing the photoresist. CONSTITUTION:The surface of a board 2 formed with a layer 8 necessary to be processed by patterning is coated with patterning photoresist 1. Then, the photoresist 1 is brought into contact with alkaline solution in a short time thereby to remove resin on the surface of the photoresist 1. Then, after a pattern is transferred to the photoresist 1 by the patterning exposure, the photoresist 1 is developed. For example, the exposure pattern is transferred through a mask 5 by using a patterning ultraviolet ray 4, and then irradiated with an ultraviolet ray 6 having a short wavelength to make the unexposed part of the photoresist 1 insoluble in alkali. Thereafter, a latent image due to the exposure is developed by developer such as alkaline solution, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine pattern forming method, and more particularly to a fine pattern forming method in a photolithography process.

[0002]

2. Description of the Related Art Conventionally, with the high integration of various devices such as semiconductor integrated circuits, printed circuit boards, control parts, etc., a method for forming a fine pattern by a lithography technique has been studied and put into practical use. A method of forming a fine pattern by a lithography technique using a general positive photoresist will be described with reference to FIG.

First, a photoresist (1) is applied to a layer which requires patterning, for example, a substrate (2) on which an oxide film (8) is formed (FIG. 3A). After that, the exposure pattern is transferred onto the photoresist (1) by irradiating the patterning ultraviolet ray (4) through the mask (5) on which the pattern is formed (FIG. 3).
(B)).

Next, the photoresist (1) to which the resist pattern has already been transferred is irradiated with ultraviolet rays (6) having a short wavelength, and P of the unexposed portion contained in the photoresist (1) is irradiated.
Suitable for making the unexposed part of the photoresist (1) insoluble in alkali and promoting the polymerization reaction by polymerizing AC (Photo Active Compound: unphotosensitive group) (1b) and resin (1a) The substrate (2) is heated at, for example, a hot plate (7) or the like (FIG. 3C).

Then, the latent image formed by exposure is developed with a developing solution (3) such as an alkaline solution to form a resist pattern (FIG. 3 (d)). In the resist pattern thus formed, when the positive photoresist (1) is exposed through the mask (5), as shown in FIG. ) Means that PAC (1b) is present, and the photosensitive group (1c) is present at the other portion. Then, by irradiating the exposed substrate (2) with ultraviolet rays (6) having a short wavelength,
The PAC (1b) on the surface of the photoresist (1) is the resin (1
A polymer (1d) with a) is formed to make it alkali insoluble.

[0006]

In the above-mentioned fine pattern forming method, the PAC (1b) of the unexposed portion contained in the photoresist (1) is exposed by irradiating the ultraviolet rays (6) of short wavelength after the patterning exposure. ) And the resin (1a) are polymerized to make the unexposed portion of the photoresist (1) sparingly soluble in alkali, but the photoresist (1) contains a larger amount of the resin (1a) than the photosensitive group. PAC to
There is a problem that the degree of polymerization between (1b) and the resin (1a) becomes small, and the unexposed portion of the photoresist (1) is slightly dissolved during development to deteriorate the resist pattern.

Further, even when the intensity of the diffracted light from the mask (5) becomes large, there is a problem that the patterning focus shifts and the resist pattern deteriorates. The present invention has been made in view of such problems, and an object thereof is to provide a fine pattern forming method capable of preventing deterioration of a resist pattern due to a focus shift during patterning exposure.

[0008]

In order to solve the above-mentioned problems, according to the present invention, a step of applying a photoresist for patterning to a surface of a substrate on which a layer requiring patterning is formed. And a step of removing the resin on the photoresist surface by bringing the photoresist into contact with an alkaline solution for a short time, and a step of developing the photoresist after transferring the pattern to the photoresist by patterning exposure. ..

[0009]

According to the method described above, the step of applying a photoresist for patterning to the surface of the substrate on which the layer requiring patterning processing is formed and the step of bringing the photoresist into contact with an alkaline solution for a short time By including the step of removing the resin on the photoresist surface and the step of developing the photoresist after transferring the pattern to the photoresist by patterning exposure, first,
As shown in FIG. 2A, a patterning photoresist (1) is applied to the surface of a substrate (2) on which a layer (8) requiring patterning is formed and then developed with an alkaline solution or the like. The resin (1a) in the surface layer of the photoresist (1) is impregnated with the liquid (3) to reduce the film in the developer (3) such as an alkaline solution, and the photoresist (1) is relatively removed.
Increasing the concentration of photosensitive groups (1c) in the surface layer (Fig. 2
(B)).

Then, a high concentration of P is formed on the surface layer of the photoresist (1) masked by the patterning exposure.
After placing the AC (1b) (FIG. 2C), the high concentration PAC (1b) of the surface layer of the photoresist (1) is polymerized with the resin (1a) by irradiating with ultraviolet rays (6) of short wavelength. To make it insoluble in alkali. That is, by making the surface layer of the photoresist (1) rich in PAC (1b) before exposure, the proportion of the polymerization reaction between the PAC (1b) and the resin (1a) increases, and the unexposed portion is more hardly alkali-soluble. Therefore, the contrast of the exposed and unexposed areas of the photoresist (1) at the time of development is improved. Therefore, even when the intensity of the diffracted light from the mask (5) is increased, the margin for defocusing at the time of patterning is expanded, and a fine resist pattern is formed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fine pattern forming method in a photolithography process according to the present invention will be described with reference to the drawings. It should be noted that components having the same functions as those of the conventional example are designated by the same reference numerals. In FIG. 1 (a),
(2) shows a substrate, and an oxide film (8) which needs to be processed is formed on the substrate (2) by patterning. Further, the adsorbed material on the surface of the substrate (2) is removed before the photoresist (1) is applied, and a heat treatment is performed to improve the adhesion between the photoresist (1) and the substrate (2). .. A photoresist (1) for patterning, for example, a positive type OFPR-5, is formed on the substrate (2).
000 (manufactured by Tokyo Ohka Co., Ltd.) by spin coating.
1 μm is applied (FIG. 4A).

Next, the substrate (2) coated with the photoresist (1) is treated with an alkaline solution of 2.38 wt% N 2.
A developer (3) of MD-3 (manufactured by Tokyo Ohka Co., Ltd.) is impregnated with the developer (3) for at least 10 seconds to dissolve and remove only the resin (1a) of the surface layer of the photoresist (1) (FIG. 4 (b)). At this time, the photoresist (1) against the high-concentration developer (3)
The surface layer dissolves about 800Å / min.

After that, the ultraviolet rays (4) for patterning are applied through the mask (5) on which the pattern is formed, using the g-line, for a time to obtain a desired line width at a wavelength of 436 nm, for example, usually a line width of 1 μm. The exposure pattern is transferred onto the photoresist (1) by irradiating it with 150 mJ (FIG. 4C). Next, photoresist (1)
The resist pattern transferred onto the photoresist (1) is irradiated with short-wavelength ultraviolet light (6), for example, at a wavelength of 200 to 500 nm at a single or multiple wavelengths and at an energy of 5 to 60 mJ / cm ^2. The PAC (1b) in the unexposed portion contained and the resin (1a) are polymerized. As a result, the unexposed portion of the photoresist (1) becomes insoluble in alkali. Also, at the same time as the irradiation of short wavelength ultraviolet rays (6),
Suitable temperature for promoting the polymerization reaction, for example 80 to
The substrate (2) is heated at 130 ° C. for 15 to 120 seconds by, for example, a hot plate (7) (FIG. 4 (d)).

Then, the latent image formed by exposure is developed with a developing solution (3) such as an alkaline solution to form a resist pattern (FIG. 4 (d)). In the fine pattern thus formed, whether or not the resin on the resist surface was actually removed by the alkaline solution is evaluated by measuring the amount of sulfur, which is a component of PAC, by the FTIR analysis method.

In the above-described embodiment, the substrate (2) coated with the patterning photoresist (1) is impregnated with the developing solution (3) and the resin (1a) on the surface layer of the photoresist (1) is treated with an alkali. The film is reduced in the developing solution (3) such as a solution to relatively increase the concentration of the photosensitive group (1c) in the surface layer of the photoresist (1). Then, the high-concentration PAC (1b) in the surface layer of the photoresist (1) is polymerized with the resin (1a) by irradiating with ultraviolet rays (6) having a short wavelength to make it insoluble in alkali. That is, the ratio of the polymerization reaction between the PAC (1b) and the resin (1a) can be increased in the surface layer of the photoresist (1), and the contrast between the exposed and unexposed areas of the photoresist (1) during development can be increased. Can be improved. Therefore, even when the intensity of the diffracted light from the mask (5) is increased, the margin for defocusing at the time of patterning is widened, and it becomes possible to form a fine resist pattern such as a vertical shape.

In the above embodiment, the case where the substrate (2) on which the oxide film (8) is formed is used as the substrate (2) on which the layer requiring patterning is formed. For example, the layer is not limited to the oxide film (8) as long as it is a layer such as a polysilicon film, an insulating film, or a metal film that requires processing by patterning. In addition, OFPR-5 is used as a positive photoresist.
However, other positive type photoresists may be used, and a negative type photoresist such as OMR-83 (manufactured by Tokyo Ohka Co., Ltd.) may be used.
Etc. may be used. In addition, the photoresist is 1.1 μm
The case of coating is explained, but 0.1 to 3.0
There is no particular limitation as long as it is in the range of μm. Further, although the case where 2.38 wt% of NMD-3 is used is described as an example of the developing solution, for example, a developing solution such as an alkaline solution which is used for developing other ordinary resists can be used. .. Further, although the case where the g-ray is used as the patterning ultraviolet ray is described,
For example, irradiation can be performed at 365 nm when using i-line, and at 254 nm when using an excimer laser.

[0017]

According to the fine pattern forming method of the present invention, a step of applying a photoresist for patterning to the surface of a substrate on which a layer requiring patterning is formed, and the photoresist is treated with an alkaline solution. A substrate coated with a photoresist for patterning, including a step of removing the resin on the photoresist surface by contacting the photoresist for a short time, and a step of developing the photoresist after transferring the pattern to the photoresist by patterning exposure. Can be impregnated with a developing solution to reduce the resin of the photoresist surface layer into a developing solution such as an alkaline solution, thereby relatively increasing the photosensitive group concentration of the photoresist surface layer. Then, the high-concentration PAC of the photoresist surface layer can be polymerized with the resin by irradiating it with ultraviolet rays having a short wavelength to make it insoluble in alkali. That is, by increasing the ratio of the polymerization reaction between PAC and the resin in the photoresist surface layer, it is possible to improve the contrast between the exposed and unexposed areas of the photoresist during development. Therefore, even when the intensity of the diffracted light from the mask is increased, the margin for the focus shift at the time of patterning is widened, and it becomes possible to form a fine resist pattern.

[Brief description of drawings]

1A to 1E are schematic sectional views for explaining an embodiment of a fine pattern forming method according to the present invention.

2A to 2D are schematic views for explaining a composition in a photoresist during a fine pattern forming step.

3A to 3D are schematic cross-sectional views for explaining a manufacturing process of a conventional fine pattern forming method.

4A and 4B are schematic views for explaining a step of removing a resin contained in a photoresist.

[Explanation of symbols]

 1 Photoresist 1a Resin 2 Substrate 8 Oxide film (layer)

Claims (1)

[Claims] 1. A step of applying a photoresist for patterning to the surface of a substrate on which a layer requiring processing by patterning is formed, and a resin on the photoresist surface by bringing the photoresist into contact with an alkaline solution for a short time. And a step of transferring the pattern to the photoresist by patterning exposure and then developing the photoresist.