JPH07111237A - Formation of resist pattern - Google Patents

Abstract

PURPOSE:To stabilize a fine pattern almost close to the resolution limit of an aligner, by forming a second resist on the area where the first resist pattern surface is not completed, then developing the first pattern to remove. CONSTITUTION:A first positive resist film 12 is formed on the surface of a SiO2. A mask 13 where a pattern opposite to a targeted pattern is formed is used to expose and develop the first positive resist film 12 so that the first resist pattern 12a is formed. A second positive resist film 14 is formed at a part where that first resist pattern 12a is not formed, then, it is developed to eliminate the first resist pattern 12a. This enables a fine pattern almost close to the resolution limit of an aligner to be formed stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a resist pattern, and more particularly to a method of forming a resist pattern used in a photolithography process in the manufacturing process of semiconductor devices and other thin film elements.

[0002]

2. Description of the Related Art Conventionally, in the process of manufacturing a semiconductor device (semiconductor integrated circuit), a resist pattern has been used as an etching mask for forming wirings and electrodes and an ion implantation mask for forming an impurity diffusion layer. ing.
A photolithography process is used to form such a resist pattern.

There are a positive type resist and a negative type resist used in the photolithography process. For example, when a positive type resist made of a photosensitive polymer is used, a circuit designed pattern is When the resist film is exposed to light through the formed mask and developed, the resist in the exposed part is removed, and a resist pattern to which the pattern is transferred is formed. On the other hand, when a negative resist is used, contrary to the case of the positive resist, the resist in a portion not exposed to light is removed, and a resist pattern in which a pattern opposite to the mask pattern is transferred is formed. .

A general photolithography process for forming a resist pattern using a positive resist will be described with reference to FIG. First, for example, a SiO ₂ film 31 is formed on a substrate (not shown), then a positive resist film 32 made of a photosensitive polymer is formed by spin coating, and then prebaking is performed to remove the positive resist film 32. The organic solvent contained in is removed (FIG. 3A).
Next, exposure is performed using the mask 33 (FIG. 3B),
Then develop. After that, post-baking is performed to cure the positive type resist film 32, improve the adhesion to the SiO ₂ film 31, and form a resist pattern 32a corresponding to the pattern of the mask 33 (FIG. 3C).

By the way, in recent years, as the degree of integration of semiconductor devices has become higher, further miniaturization and higher density of circuit patterns have been required, and nowadays, fine resist patterns close to the resolution limit of the exposure apparatus can be stably provided. It is required to form.

In the photolithography process, the intensity distribution of light transmitted through the mask 33 during exposure differs depending on the width of the light transmitting portion of the mask 33. That is, when the width of the light transmitting portion is wide, sufficient intensity can be obtained in all the portions where the light is transmitted as shown in FIG. 4. Therefore, when a positive resist is used, as shown in FIG. A resist pattern 32a having a different shape is formed. However, when the width of the light transmitting portion is narrow, it is difficult to obtain sufficient intensity as shown in FIG. 6, and the light intensity becomes weaker from the central portion of the light transmitting portion to the outside. Therefore, for example, when the mask 33 having a fine pattern close to the resolution limit of the exposure apparatus is used, the bottom of the positive type resist film 32 cannot be sufficiently exposed, and as a result, as shown in FIG. A resist pattern 32a whose bottom is not removed is formed. Therefore, there is a problem that a fine pattern close to the resolution limit of the exposure apparatus cannot be stably formed.

Therefore, in order to solve such a problem,
As a method of forming a fine resist pattern close to the resolution limit of the exposure apparatus, a resist columnar body having a bottom portion with a fine width is formed using a pattern opposite to the target pattern, and then this resist columnar body is formed into a second pattern. A method of covering with a resist film and then removing the resist columnar body and the second resist film on the resist columnar body is proposed (Japanese Patent Laid-Open No. 5-29186).

FIG. 8 is a schematic sectional view showing each step for explaining the method of forming a resist pattern described in Japanese Patent Laid-Open No. 5-29186. First, the first positive resist film 42 is formed on the surface of the SiO ₂ film 41 formed on the substrate (not shown) by spin coating (FIG. 8).
(A)). After that, exposure is performed using the first mask 43 having a pattern opposite to the target pattern (see FIG. 8).
(B)) The resist columnar body 42a after the first development
Are formed (FIG. 8C).

Next, the resist columns 42a and SiO _{2 are formed.}
The resist pillars 4 are formed by coating the entire surface of the film 41.
A second positive resist film 44 having a thickness larger than 2a is formed. (FIG.8 (d)). Next, the second mask 45 on which the desired pattern is formed is used to expose the portion of the second positive resist film 44 indicated by the broken line (FIG. 8).
(E)). After that, the second development is performed to expose the exposed portion of the second positive resist film 44 and the first resist columnar body 4.
2a is removed to form a resist pattern 44a (FIG. 8 (f)).

[0010]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the method of forming a resist pattern described in Japanese Patent No. 9186, although the shape of the resist columnar body 42a can be a fine pattern close to the resolution limit of the exposure apparatus, a step of forming the second positive resist film 44, There is a problem that the process is complicated because the second exposure process and the development process are added.

In the second exposure / development, it is necessary to expose and develop only the unexposed resist columnar body 42a and the exposed portion of the second positive resist film 44 covering it. However, there is a problem that the positive resist and the developing solution that can be used are limited at the same time.

The present invention has been made in view of the above problems, and various positive resists and developing solutions can be used, and a fine pattern close to the resolution limit of the exposure apparatus can be stably and simplified. It is an object of the present invention to provide a method for forming a resist pattern that can be formed in various steps.

[0013]

In order to achieve the above object, a resist pattern forming method (1) according to the present invention comprises:
It is characterized by including the following steps.

A first positive resist film is formed on the surface of the material forming the resist pattern.

The first positive resist film is exposed using a mask having a pattern opposite to the target pattern.

Development is performed to form a first resist pattern.

Whole surface exposure is performed.

A second resist film is formed on a portion of the surface of the material where the first resist pattern is not formed.

The developed first resist pattern is removed.

The resist pattern forming method (2) according to the present invention is characterized by including the following steps (a) to (g).

(A) A first positive resist film is formed on the surface of the material forming the resist pattern.

(A) The first positive resist film of (a) is exposed using a mask having a pattern opposite to the target pattern.

(C) Develop to form a first resist pattern.

(D) Whole surface exposure is performed.

(E) The surface of the material and the first of (c)
A second resist film is formed on the entire surface of the resist pattern.

(F) Exposure is performed so that the second resist film of (e) formed on the first resist pattern of (u) can be removed.

(G) By developing, the removable portion of the second resist film and the first resist pattern of (C) are removed.

[0028]

According to the resist pattern forming method (1) having the above-described structure, a mask in which the first positive type resist film is formed on the surface of the material for forming the resist pattern and the pattern opposite to the intended pattern is formed. Since the first positive resist film is exposed by using the mask, even if the target pattern has a fine pattern width close to the resolution limit of the exposure apparatus, the mask having a wide light transmitting portion is used. It becomes possible to perform exposure, and it becomes possible to sufficiently expose the bottom of the first positive resist film. Therefore, the first resist pattern in which the diameter of the bottom of the resist remaining portion is fine is formed. Next, by exposing the entire surface,
It is possible to keep the entire first resist pattern in a developable state. In addition, since the second resist film is formed on a portion of the surface of the material where the first resist pattern is not formed, and then developed to remove the first resist pattern, A resist pattern having a shape opposite to the shape is formed.
Therefore, by using such a resist pattern, it becomes possible to stably form a fine pattern close to the resolution limit of the exposure apparatus.

Further, since the second resist film is not formed on the first resist pattern, it is not necessary to expose and develop the second resist film, and the process is greatly simplified. Further, any type of positive resist can be used for the first positive resist film and the second resist film.

Further, since the entire surface of the first resist pattern is exposed, it is not necessary to develop the unexposed first resist pattern in the subsequent development as in the conventional example. It is possible to use a normal positive resist developing solution. In this case, either a positive type resist or a negative type resist may be used for the second resist film, and depending on the purpose, a resin which is not called a normal resist but has no photosensitivity may be used.

Further, in the resist pattern forming method (2) having the above-mentioned structure, since the first resist pattern is formed by the same method as (1) and the entire surface is exposed, the diameter of the bottom of the resist remaining portion is reduced. It is possible to keep the entire fine first resist pattern in a developable state. Further, a second resist film is formed on the surface of the material forming the resist pattern and the entire surface of the first resist pattern, and the second resist film formed on the first resist pattern can be removed. Since the first exposure is performed, the exposure condition is selected and the first exposure is performed.
It becomes possible to expose only the second resist film on the resist pattern to the taper shape to make it developable. Further, since the removable portion of the second resist film and the first resist pattern are removed by development, a resist pattern having a shape substantially opposite to the shape of the first resist pattern is formed. Therefore, by using such a resist pattern, it becomes possible to stably form a fine pattern close to the resolution limit of the exposure apparatus.

Further, it is possible to use an ordinary resist developer. The second resist film may be either a positive type or a negative type,
When the same type of the first positive type resist film is used, any type of positive type resist may be used, and when different types of positive type resist films are used, the same developing solution is used. It is preferable to use one having the reactivity of. When a negative type is used, the mask for exposing the first positive resist film and the mask for exposing the second resist film may be the same, and the mask manufacturing process may be simplified. It will be possible.

[0033]

Embodiments of the method of forming a resist pattern according to the present invention will be described below with reference to the drawings. Here, a case where an exposure device (not shown) having a resolution limit of 0.5 μm is used to form a resist pattern having a pattern width of about 0.4 μm will be described as an example.

[Embodiment 1] FIGS. 1A to 1F are schematic sectional views showing respective steps for explaining a method of forming a resist pattern according to Embodiment 1. First, the surface of, for example, a SiO ₂ film 11 formed on a substrate (not shown) is spin-coated with, for example, PEX15 (manufactured by Sumitomo Chemical Co., Ltd.) to form a first positive resist having a thickness of 1.2 μm. The film 12 is formed. The spin coating is performed by dropping the resist solution and then spreading the whole substrate by centrifugal force while rotating the entire substrate.

Next, prebaking is performed to remove the organic solvent contained in the first positive resist film 12 (FIG. 1).
(A)). After that, using the above-mentioned exposure apparatus, using a mask 13 in which a pattern opposite to the target pattern is formed with a pattern width of about 0.5 μm, the exposure condition is an exposure amount of 4
The exposure time is set to 800 ms at 00 mJ / cm ² and g
Exposure using a line (exposure wavelength: 436 nm)
The part indicated by the broken line of the positive type resist film 12 is made ready for development (FIG. 1B). Then, for example, NMD
-3 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is used to form a first resist pattern 12a having a diameter of the bottom of the remaining resist portion of about 0.4 μm (FIG. 1C).

After that, the entire surface is exposed with an exposure amount of 400 mJ / cm ² and an exposure time of 800 ms, so that the entire first resist pattern 12a is ready for development (FIG. 1).
(D)). Next, for example, PEX is formed on the surface of the SiO ₂ film 11 where the first resist pattern 12a is not formed.
The second positive type resist film 14 having a thickness of 1.0 μm is formed so as not to cover the first resist pattern 12a by spin coating 15 with adjusting the viscosity and the amount (FIG. 1 (e)). . Next, for example, development is performed using NMD-3 to remove the first resist pattern 12a. After that, baking is performed at 120 ° C. for 120 seconds to remove the organic solvent contained in the second positive resist film 14 and to cure the resist, and the diameter of the bottom portion of the resist removed portion is about 0.
A resist pattern 14a of 4 μm is formed (see FIG. 1).
(F)).

In the method of forming the resist pattern 14a according to this embodiment, the mask 13 is formed by forming the first positive resist film 12 on the surface of the SiO ₂ film 11 and forming a pattern opposite to the target pattern. Since the first positive resist film 12 is exposed by using a mask 13, a mask 13 having a wide light transmitting portion is used even if the target pattern width is about 0.5 μm which is almost the same as the resolution limit of the exposure apparatus. Exposure can be performed, and the bottom of the first positive resist film 12 can be sufficiently exposed. Further, since the resist is developed to form the first resist pattern 12a, the first resist pattern 12a having a diameter of the bottom of the resist remaining portion of about 0.4 μm can be formed. Next, by exposing the entire surface, the entire first resist pattern 12a can be surely developed in a stage before the second positive resist film 14 is formed. Further, the second positive type resist film 14 is formed on the portion of the surface of the SiO ₂ film 11 where the first resist pattern 12a is not formed, and then developed to remove the first resist pattern 12a. A resist pattern 14a having a shape opposite to that of the resist pattern 12a is formed. Therefore, by using such a resist pattern 14a, a pattern close to the resolution limit of the exposure apparatus and finer than the exposure wavelength can be stably formed.

Further, the diameter of the bottom portion of the resist-removed portion of the resist pattern 14a is set to about 0.4 μm by changing the exposure condition when exposing the first positive type resist film 12.
It can be arbitrarily set within a range of up to 5.0 μm.

Further, the second positive resist film 14 is not formed on the first resist pattern 12a,
Since it is not necessary to expose and develop the second positive resist film 14, the process can be greatly simplified.

Further, as the developing solution, an ordinary developing solution can be used, which is different from the developing solution described in the prior art.

Further, a SiO ₂ film 11 is used as a base material.
Other than Si substrate, metal film, etc. may be used.

In this embodiment, the exposure wavelength is 436 nm.
However, in another embodiment, an i-line or the like having an exposure wavelength of 365 nm may be used. i
When a line is used, the resist pattern 14a having a pattern width of about 0.3 μm can be formed.

In this embodiment, the case where PEX15 is used for the first positive type resist film 12 has been described.
In another embodiment, any other type of positive resist may be used for the first positive resist film 12.

Further, in the present embodiment, the case where the PEX 15 is used for the second positive type resist film 14 has been described, but in other examples, any other type of positive type resist may be used. Instead of the positive resist film 14 of No. 2, a negative resist film or a resin film which is not called a resist but has no photosensitivity may be used depending on the purpose.

[Embodiment 2] FIGS. 2A to 2G are schematic sectional views showing respective steps for explaining a method of forming a resist pattern according to Embodiment 2. First, the surface of, for example, the SiO ₂ film 21 formed on a substrate (not shown) is spin-coated with, for example, PEX15 (manufactured by Sumitomo Chemical Co., Ltd.) to form a first positive resist having a thickness of 1.0 μm. The film 22 is formed. The spin coating is performed by dropping the resist solution and then spreading the whole substrate by centrifugal force while rotating the entire substrate.

Next, prebaking is performed to remove the organic solvent contained in the first positive resist film 22 (FIG. 2).
(A)). Then, using the above-mentioned exposure apparatus, using the first mask 23 in which a pattern opposite to the target pattern is formed with a pattern width of about 0.5 μm, the exposure condition is an exposure amount of 400 mJ / cm ² . The exposure time is set to 800 ms and the exposure is performed using the g-line, and the first positive resist film 2
The portion indicated by the broken line 2 is in a developable state (FIG. 2B). After that, development is performed using, for example, NMD-3 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) to form a first resist pattern 22a having a bottom diameter of the resist remaining portion of about 0.4 μm (FIG. 2C). ). After this, the exposure amount is 400 mJ
The entire surface of the first resist pattern 22a is exposed by the g-line exposure with an exposure time of 800 ms at / cm ² (FIG. 2 (d)).

Next, PEX15 is spin-coated on the entire surface of the SiO ₂ film 21 and the first resist pattern 22a, so that the surface of the first resist pattern 22a is reduced to 0.
A second positive resist film 24 having a thickness of about 5 μm is formed (FIG. 2E). After that, prebaking is performed to remove the organic solvent contained in the second positive resist film 24, and then the second mask 25 on which a target pattern having a pattern width of about 0.5 μm is formed is used. The exposure conditions are set to be 150 mJ / cm ² and the exposure time is set to 300 ms, and exposure is performed using the g-line so that the portion indicated by the broken line of the second positive resist film 24 is in a developable state ( FIG. 2F).

Then, development is performed using NMD-3,
The exposed portion of the second positive resist film 24 and the first resist pattern 22a are removed. After this,
Post-baking is performed at 120 ° C. for 120 seconds to cure the second positive resist film 24 and form a resist pattern 24a having a diameter of about 0.4 μm at the bottom of the resist removed portion (FIG. 2 (g)).

In the method of forming the resist pattern 24a according to the present embodiment, the first positive resist film 22 is formed on the surface of the SiO ₂ film 21, and the first pattern in which the pattern opposite to the intended pattern is formed. Since the first positive resist film 22 is exposed by using the mask 23, the width of the light transmitting portion is wide even if the target pattern width is about 0.5 μm which is almost the same as the resolution limit of the exposure apparatus. It becomes possible to perform exposure using the first mask 23, and the bottom of the first positive resist film 22 can be sufficiently exposed. In addition, since the first resist pattern 22a is formed by development, the diameter of the bottom of the resist remaining portion is about 0.4 μm.
The resist pattern 22a can be formed. Next, by exposing the entire surface, the first resist pattern 22 is formed at a stage before forming the second positive resist film 24.
The whole a is ready for development with certainty and ease. Also, S
A _second positive resist film 24 can be formed on the surface of the iO ₂ film 21 and the entire surface of the first resist pattern 22a, and the second positive resist film 24 formed on the first resist pattern 22a can be removed. Since the exposure is performed as described above, only the second positive resist film 24 on the first resist pattern 22a is exposed to the taper shape and becomes a developable state by performing the exposure by selecting the exposure condition. Further, since the removable portion of the second positive resist film 24 and the first resist pattern 22a are removed by development, the first positive resist film 24 is removed.
A resist pattern 24a having a shape substantially opposite to the shape of the resist pattern 22a is formed. Therefore, by using such a resist pattern 24a, a pattern close to the resolution limit of the exposure apparatus and finer than the exposure wavelength can be stably formed.

Further, the diameter of the bottom of the resist-removed portion of the resist pattern 24a is changed to about 0.4 μm by changing the exposure condition when exposing the first positive resist film 22.
It can be arbitrarily set within a range of up to 5.0 μm.

Further, as the developing solution, different from the one described in the conventional publication, an ordinary developing solution can be used.

In this embodiment, the case where PEX15 is used for the second positive resist film 24 has been described.
In the other embodiment, any other resist may be used, and when the positive type and the same as the first positive type resist film are used, the selection of the developing solution becomes easy. The second
When a negative resist film is used instead of the resist film 24, the mask for exposing the first positive resist film 22 and the mask for exposing the negative resist film are the same, and the mask manufacturing process is performed. It can be simplified.

[0053]

As described above in detail, in the method (1) for forming a resist pattern according to the present invention, the first positive resist film is exposed using a mask on which a pattern opposite to the target pattern is formed. Therefore, even if the target pattern has a fine pattern width close to the resolution limit of the exposure apparatus, the first positive resist film is exposed by performing exposure using the mask having a wide light transmitting portion. First, the diameter of the bottom of the remaining resist is very small.
The resist pattern can be formed. Further, by exposing the entire surface, the entire first resist pattern is made developable, and a second portion is formed on a portion of the material surface where the first resist pattern is not formed.
The resist film is formed and then developed to remove the first resist pattern, so that even a fine pattern close to the resolution limit of the exposure apparatus can be stably formed.

Further, the diameter of the bottom of the resist-removed portion of the resist pattern can be arbitrarily set by changing the exposure condition when exposing the first positive type resist film.

Furthermore, since the second resist film is not formed on the first resist pattern and there is no need to expose and develop the second resist film, the process is greatly simplified. You can Any type of resist can be used for the first positive resist film and the second resist film.

Further, as the developing solution, different from the one described in the conventional publication, a usual developing solution can be used.

Further, in the resist pattern forming method (2) according to the present invention, as in the case of the above method (1), a pattern close to the resolution limit of the exposure apparatus and finer than the exposure wavelength is stabilized. Can be formed as desired.

Further, either a positive type resist or a negative type resist may be used as the second resist film. When the same positive type resist film as the first positive type resist film is used, When the negative type is used, the mask for exposing the first positive resist film and the mask for exposing the second resist film are the same, and the mask manufacturing process is performed. It can be simplified.

[Brief description of drawings]

1A to 1F are schematic cross-sectional views showing, in the order of steps, Example 1 of a method for forming a resist pattern according to the present invention.

2A to 2G are schematic cross-sectional views showing a method of forming a resist pattern according to Example 2 in the order of steps.

3A to 3C are schematic sectional views showing a conventional general resist pattern forming method in the order of steps.

FIG. 4 shows a case where a mask having a wide light transmitting portion is used,
6 is a graph showing a light intensity distribution.

FIG. 5 shows a resist pattern formed when a mask is used for the width of a light transmitting portion.

FIG. 6 shows a case where a mask having a narrow light transmitting portion is used,
6 is a graph showing a light intensity distribution.

FIG. 7 shows a resist pattern formed when a mask having a narrow light transmitting portion is used.

8A to 8F are schematic cross-sectional views showing another conventional method of forming a resist pattern in order of steps.

[Explanation of symbols]

11, 21 SiO ₂ film (material for forming resist pattern) 12, 22 first positive resist film 12a, 22a first resist pattern 13 mask 14, 24 second positive resist film 14a, 24a resist pattern 23 First mask

Claims (2)

[Claims] 1. A first positive resist film is formed on a surface of a material for forming a resist pattern, and the first positive resist film is exposed by using a mask having a pattern opposite to a target pattern. After developing to form a first resist pattern and performing overall exposure, a second resist film is formed on a portion of the surface of the material where the first resist pattern is not formed, and then developed. A method of forming a resist pattern, which comprises removing the first resist pattern. 2. A first positive resist film is formed on the surface of a material for forming a resist pattern, and the first positive resist film is exposed by using a mask having a pattern opposite to a target pattern. After developing to form a first resist pattern and exposing the entire surface, a second resist film is formed on the surface of the material and the entire surface of the first resist pattern, and the second resist film is formed on the first resist pattern. Exposed so that the second resist film formed on
A method of forming a resist pattern, which is characterized by developing thereafter to remove the removable portion of the second resist film and the first resist pattern.