JP2551117B2 - Resist pattern formation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a resist pattern by selectively exposing a resist layer formed by applying a photoresist on a substrate and then developing the resist layer. It is a thing.

[Conventional technology]

In the manufacturing process of semiconductor devices and the like, a photoresist is applied on a substrate to form a resist layer, a mask pattern is transferred by exposure and developed to form a predetermined resist pattern, and the resist pattern is formed. Etching is performed as a mask. An image reversal method is known as a method for forming such a resist pattern.

FIG. 3 is a flow chart showing the process of the conventional image reversal method, and the process will be described below with reference to this figure. First, photoresist on the substrate,
For example, in a positive photoresist containing naphthoquinonediazide as a photosensitizer in phenol novolac resin,
A resist layer is formed by applying a solution to which triethanolamine or the like has been added as a catalyst, prebaking it to remove the volatile organic solvent, and drying. Next, the first exposure (hereinafter referred to as the first exposure) is performed by selectively irradiating far ultraviolet rays or the like through a mask on which a desired pattern is drawn. At this time, the exposed portion of the resist layer (hereinafter referred to as the first exposed portion) undergoes a photoreaction and becomes soluble in the developing solution. After that, reverse baking is performed at about 100 ° C. to 130 ° C., and the first exposed portion reacts and cures by the action of the catalyst, and becomes insoluble in the developing solution. Next, the entire surface of the resist layer including the first exposed portion is exposed (hereinafter referred to as second exposure), and the unexposed portion at the time of the first exposure becomes soluble in the developing solution due to a photoreaction. Then, an organic alkaline developer, for example, trimethylammonium hydroxide 2.
By developing with a 38% aqueous solution, only the unexposed portion at the time of the first exposure is selectively removed, and a resist pattern corresponding to the reverse image of the mask is obtained.

FIG. 4 is a cross-sectional view showing the resist layer in the above process, and FIG. 4 (A) shows a state after reverse baking, in which (1) is a substrate and (2) is above it. A resist layer formed on the substrate, (3) is an unexposed portion that is behind the pattern of a mask (not shown) during the first exposure,
(4) is the first exposed area, which is cured by reversal baking and is insoluble in the developing solution. FIG. 4 (B) shows a state at the time of the second exposure, in which the unexposed portion (3) at the time of the first exposure reacts with the light (5) emitted from above to be soluble in the developing solution. Becomes FIG. 4 (C) shows a developed state, in which the unexposed portion (3) at the time of the first exposure is removed and the first exposed portion (4) remains to form a pattern.

[Problems to be Solved by the Invention]

Since the conventional resist pattern forming method is performed as described above, as the light at the first exposure enters the resist layer, it is attenuated due to the light absorption of the resist layer, and the resist layer close to the substrate is obtained. Since sufficient photoreaction does not occur in the lower layer part of the lower part, due to the catalytic action during reverse baking,
The reaction to cure the first exposed portion and make it insoluble in the developing solution becomes insufficient as compared with the upper layer portion. Therefore, at the time of development, the lower layer portion of the first exposed portion has a higher dissolution rate than the upper layer portion, and the shape of the remaining resist pattern is as shown in the first exposed portion (4) of FIG. There is a problem in that the processing accuracy becomes poor in the etching step in the subsequent semiconductor manufacturing process due to the thin undercut shape.

The present invention has been made to solve the above problems, and an object thereof is to prevent undercut of a resist pattern and improve its shape.

[Means for solving the problem]

A method of forming a resist pattern according to the present invention comprises selectively exposing a part of a resist layer formed on a substrate to a first exposure to form an exposed portion, curing the exposed portion to render it insoluble in a developing solution, and then exposing the exposed portion. Second exposure of the entire surface of the resist layer including the part,
In the resist pattern forming method of forming a pattern by selectively removing the unexposed portion at the first exposure by performing development while making the unexposed portion at the first exposure soluble in a developing solution, the exposed portion is made insoluble. After that, the second exposure area is 200nm-300
The step of exposing the entire surface of the resist layer with light having a wavelength of nm to expose the unexposed portion to a predetermined depth and developing the exposed portion is performed a plurality of times to remove the unexposed portion.

[Action]

In the method of forming a resist pattern according to the present invention, the entire surface of the resist layer is exposed and developed a plurality of times, and the unexposed portion at the time of the first exposure is removed a plurality of times, so the lower layer portion of the unexposed portion is removed. Therefore, when the entire surface is exposed, the first exposed portion becomes a mask and the light does not sufficiently reach the portion that is behind the first exposed portion, so that the portion remains insoluble.
This portion remains without being removed during development.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a flow chart showing a process of a resist pattern forming method according to an embodiment of the present invention, which will be described below. The process from resist coating to reverse baking is the same as in the conventional example of FIG. After the reverse baking, the entire surface of the resist layer including the first exposed portion is exposed (hereinafter referred to as second exposure). In this case the wavelength is 200n
Light of approximately m to 300 nm, for example, light having a relatively short wavelength, such as light with a wavelength of 254 nm of an ultra-high pressure mercury lamp, is exposed and the light transmittance is low. Although it becomes soluble in the developing solution by photoreacting up to about half the thickness of the side, for the thickness of about half of the substrate side of the unexposed portion,
It does not reach enough light, so it does not undergo photoreaction and remains insoluble. Then, an organic alkaline developer, for example,
2.38% of tetramethylammonium hydroxide
When developed with the above aqueous solution for 30 seconds (hereinafter referred to as the first development) and washed with pure water, approximately half the thickness of the surface side of the above-described photo-exposed unexposed portion is removed, and photo-reaction is caused. About half of the non-board side remains. Further, the entire surface exposure (hereinafter referred to as the third exposure) and the development (hereinafter referred to as the second development) are repeated again in the same manner as above. As a result, about half of the unexposed portion remaining on the substrate side is removed.

FIG. 2 is a cross-sectional view showing the resist layer in the above process, and FIG. 2 (A) shows a reverse baking, which is the same as the case of the conventional example of FIG. 4 (A). Omit it. FIG. 2B shows the time of the second exposure.
In the figure, (6) is an upper layer portion on the front surface side of the unexposed portion (3) at the time of the first exposure, and (7) is a lower layer portion on the substrate side, which is light (5) irradiated from above in the figure. Thus, the upper layer portion (6) reacts and becomes soluble in the developing solution. However, since the transmittance of the light (5) is low, sufficient light (5) does not reach the lower layer portion (7), and therefore, the photoreaction does not occur and it remains insoluble. FIG. 2 (C) shows a state in which the first development has been performed. The upper layer portion (6) is removed but the lower layer portion (7) remains. FIG. 2 (D) shows the time of the third exposure, and the lower layer portion (7) becomes soluble by reacting with the light (5) irradiated from the upper side in the figure, but becomes shaded in the first exposed portion (4). The first exposure portion (4) serves as a mask and the light (5) does not sufficiently reach the portion (8) that becomes. That is, the light (5) is attenuated while passing through the first exposed portion (4), and the shaded portion (8) remains insoluble. FIG. 2 (E) shows a state in which the second development has been performed. The lower layer portion (7) is removed, but the shadowed portion (8) of the first exposed portion (4) is the first portion.
The resist pattern is formed by remaining together with the exposed portion (4). Therefore, the undercut of the resist pattern is prevented.

In the above embodiment, the light (5) having the same wavelength was irradiated in the second exposure and the third exposure, but light (5) having a different wavelength may be used, or the first development and the second development. The same conditions were used, but different types of developing solutions or different lengths of time may be used. Furthermore, the example in which the entire surface exposure and the development are performed twice has been shown. However, by appropriately selecting the wavelength (5) of the light (5) used during the entire surface exposure and the irradiation time, the resist can be removed by the entire surface exposure and the development once. The number of times can be arbitrarily selected by adjusting the thickness of the layer (2).

〔The invention's effect〕

As described above, according to the present invention, since the entire surface exposure and development of the resist layer are performed a plurality of times, during the entire surface exposure for removing the lower layer portion of the unexposed portion during the first exposure, the first exposed portion Since the first exposed portion serves as a mask in the shaded portion, it remains insoluble, so that this portion remains without being removed during development, undercutting of the resist pattern is prevented, and its shape is improved. effective.

[Brief description of drawings]

FIG. 1 is a flow chart showing a process of a pattern forming method according to an embodiment of the present invention, FIG. 2 is a sectional view showing a resist layer in the process of FIG. 1, and FIG. 3 is a process of a conventional pattern forming method. Flow chart, 4th
The figure is a cross-sectional view of the resist layer during the process of FIG. In the figure, (1) is a substrate, (2) is a resist layer,
(3) is an unexposed area, (4) is a first exposed area, and (5) is light. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A part of a resist layer formed on a substrate is selectively exposed to a first exposure to form an exposed part, and the exposed part is cured to make it insoluble in a developing solution, and then the exposed part is also included. Second exposure is performed on the entire surface of the resist layer, and the unexposed portion at the first exposure is made soluble in the developing solution to perform development to selectively remove the unexposed portion at the first exposure. In the resist pattern forming method of forming a pattern by
After making the exposed area insoluble, the second exposed area is adjusted to 200 nm.
Characterized in that the unexposed portion is removed by performing the step of exposing the unexposed portion to a predetermined depth by exposing the entire surface of the resist layer with light of up to 300 nm and developing the exposed portion a plurality of times. Resist pattern forming method.