JP2870443B2 - Method of forming resist pattern - Google Patents

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 resist pattern in the manufacture of semiconductor devices.

[0002]

2. Description of the Related Art In forming a pattern on a positive resist layer, diffraction of light from a mask hinders miniaturization. That is, since light diffracted from the mask shines on the resist layer near the opening of the mask at the time of exposure, the resist layer at this portion dissolves at the time of exposure in the same manner as the exposed portion, thereby preventing miniaturization. As a means for solving such a problem, there is a method of modifying a positive resist layer with an aqueous alkaline solution. In this method, a semiconductor substrate having a positive resist layer formed thereon is immersed in an aqueous alkaline solution before exposure to form a poorly soluble layer on the surface of the resist layer. According to this method, the portion irradiated with the light diffracted from the mask is not melted by etching like the other unexposed portions, so that a fine pattern can be formed relatively favorably.

[0003]

However, the pattern shape cannot be improved to a sufficient level by the above-described method for modifying an alkaline aqueous solution.

Accordingly, an object of the present invention is to provide a method capable of easily and favorably forming a fine pattern on a positive resist layer.

[0005]

In order to achieve the above object, the present invention provides a first step of forming a positive resist layer containing a naphthoquinonediazide-based substance and a phenol-based resin on a main surface of a substrate; A second step of permeating an aqueous alkaline solution on the surface side of the positive resist layer to form a portion formed by combining the naphthoquinonediazide-based material and the phenolic resin on the front surface of the positive resist layer; the substrate-side portion of the resist layer is or weakly dried without drying, the positive type Regis surface side portion of the positive type resist layer was strongly dried than the portion of the substrate side
A relatively high moisture layer on the substrate side of the layer
Water relative to the surface-side portion of the positive resist layer.
A third step of forming a layer having a small number of layers, a fourth step of selectively exposing a predetermined region of the positive resist layer using a mask, and developing the positive resist layer by developing the positive resist layer. Selectively removing the predetermined region of the shaped resist layer. The drying is performed as described in claim 2 or 3.
It is desirable to do so. Also, as shown in claim 4
It is desirable to provide a heat treatment step.

[0006]

According to the present invention, the following functions and effects can be obtained. (A) Since the surface side of the resist layer is dried, moisture on the surface side of the resist layer is reduced, the light incidence rate on the surface of the resist layer is increased, and the generation of indenecarboxylic acid is promoted. (B) During the drying of the resist, the moisture on the surface of the resist layer penetrates into the resist layer, and the moisture is relatively abundant inside the resist layer. A relatively large amount of acid can be generated inside the resist layer. (C) By the above (a) and (b), the etching rate of the exposed portion of the resist layer, that is, the etching speed can be made higher than in the conventional example. Therefore, the etching rate of the exposed portion of the resist layer can be made higher than that of the conventional example, while the etching rate of the portion of the resist layer irradiated with the diffracted light from the mask remains low as in the conventional example. As a result, the phenomenon time required to remove the exposed portion as desired can be shortened, so that the dissolution of the resist layer in the portion irradiated with the diffracted light from the mask can be sufficiently reduced, and the pattern shape can be improved.

[0007]

Next, a method for manufacturing a semiconductor device according to an embodiment of the present invention will be described with reference to FIGS. In this embodiment, first, a semiconductor substrate 2 having a positive resist layer 1 formed on one main surface as shown in FIG. 1 is prepared. The positive resist layer 1 contains a solvent such as naphthoquinonediazide, a phenol resin, and ethyl cellosolve acetate. The positive resist layer 1 of this embodiment is about 1.2 μm
And formed by coating using a known spinner.

Next, the semiconductor substrate 2 of FIG.
Pre-bake (heat treatment) for 90 seconds is performed, and the resist layer 1
The solvent therein was evaporated. By this pre-baking, the resist layer 1 and the semiconductor substrate 2 are brought into good contact with each other, and the resist layer 1 is prevented from adhering to the mask during the later-described exposure. In addition, when the prebaking is insufficient and the alkali treatment described below is performed in a state where the solvent is not sufficiently volatilized, a reforming reaction described below does not easily progress well, and the reforming effect may not be sufficiently exerted. . Therefore, it is desirable that the solvent in the resist layer 1 be completely volatilized.

Next, the semiconductor substrate 2 after the prebaking was immersed in an alkaline aqueous solution (0.24 M tetramethylammonium hydroxide aqueous solution). In this example, the temperature of the alkaline aqueous solution was set to about 23 ° C., and the substrate 2 was immersed in this aqueous solution for about 60 seconds. As a result, the aqueous alkali solution permeates into the layer on the surface side of the resist layer 1, and the naphthoquinonediazide and the phenol resin in the resist layer 1 react and combine with each other by the alkali, and as shown in FIG. The poorly soluble portion 1b was formed. That is, the resist layer 1 had a two-layer structure of the inner easily soluble portion 1a having a high etching rate and the hardly soluble portion 1b on the front side having a low etching rate. Since the aqueous alkaline solution does not penetrate into the interface between the resist layer 1 and the semiconductor substrate 2, the above-described reaction and bonding do not occur, and the hardly soluble portion 1b is not formed.

Next, the semiconductor substrate 2 on which the hardly soluble portion 1b was formed was washed with pure water, and then the moisture attached to the resist layer 1 was removed by a spinner. The removal of water by the spinner is performed in an air atmosphere, but may be performed in a nitrogen atmosphere in some cases.

Next, the semiconductor substrate 2 was placed in a drying container 3 as shown in FIG. 3, and compressed air was introduced into the drying container 3 from a compressed air cylinder 4 to dry the resist layer 1. What is important here is that only the surface side of the resist layer 1 is dried, and the interface side with the semiconductor substrate 2 is not dried but water is left. The reason will be described later. In this embodiment, the compressed air is applied to the surface 5 of the semiconductor substrate 2 on the side where the resist layer 1 is not formed.
Is drying. This is to prevent compressed air from hitting the surface of the resist layer 1 and damaging the bond due to alkali modification of the resist. In this example, compressed air was introduced at a pressure of 0.2 kg / cm ² , and the resist layer 1 was dried for about 15 minutes. It is also possible to use a gas such as Ar or N2 instead of the compressed air. In this embodiment, the drying of the resist layer 1 is performed in the hardly soluble portion 1b.
To a position deeper than the hardly soluble portion 1b so as to include the entirety of By doing so, the resist layer 1 on the substrate 2 can be dried more uniformly in this plane direction .

Next, the substrate 2 is placed on a hot plate with the other main surface 5 side of the semiconductor substrate 2 (the side opposite to the resist forming surface) facing downward, and the resist layer 1 is baked at 150 ° C. for about 5 minutes. (Heat treatment). By performing the heat treatment, the bond of the hardly soluble portion 1b is strengthened, and the hardly soluble portion 1b is hardly dissolved in the etching solution.

Next, as shown in FIG. 4, a mask 6 is disposed above the resist layer 1 and the resist layer 1 is exposed using g-rays (ultraviolet light having a wavelength of about 436 nm). The resist layer 1 is exposed in a region facing the opening 7 of the mask 6 in the same manner as in the related art, and is diffracted from the mask 6 so that the resist layer 1 near the region facing the opening 7 of the mask 6 is also exposed. The g-ray is weakly irradiated. In this example, the exposure was performed at an exposure amount of about 120 mJ / cm ² with the lamp illuminance set to 30 mW and the exposure time set to 4.0 seconds.

Finally, the resist layer 1 on the semiconductor substrate 2 is developed, that is, wet-etched , to selectively remove the resist layer 1 in the region facing the opening 7 of the mask 6, ie, the exposed portion, as shown in FIG. . The resist pattern thus obtained is used as an etching mask for an insulating film, a metal film, or a semiconductor formed on the surface of the semiconductor substrate 2.

According to the present embodiment, the etching rate of the exposed portion of the resist layer 1 is lower than that of the conventional example, while the etching rate of the portion of the resist layer 1 that is irradiated with the diffracted light from the mask remains the same as in the conventional example. Can also be large. As a result, the development time required to remove the exposed portion as desired can be reduced, so that the dissolution of the resist layer 1 in the portion irradiated with the diffracted light from the mask can be sufficiently reduced, and the pattern shape can be improved.

Next, the reason why the etching rate of the exposed portion of the resist layer 1 is increased will be described. When exposed, the naphthoquinonediazide contained in the resist layer 1 reacts with water in the resist and changes to indenecarboxylic acid, which is a developer-dissolving component. According to this embodiment, a large amount of this indene carboxylic acid can be produced. That is, in the present embodiment, the following operation and effect are produced. (A) Since the surface side of the resist layer 1 is dried, the moisture on the surface side of the resist layer 1 decreases, the light incidence rate on the surface of the resist layer 1 increases, and the production of indenecarboxylic acid is promoted. (B) During the drying of the resist, the moisture on the surface of the resist layer 1 penetrates into the resist layer 1, and the moisture inside the resist layer 1 is relatively abundant. A certain indene carboxylic acid is applied to the resist layer 1
Can be generated in a relatively large amount within the. By the above (a) and (b), the etching rate of the exposed portion of the resist layer 1 can be made higher than in the conventional example.

[0017]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) Drying of the surface region of the resist layer 1 can also be achieved by spin drying. However, when drying is performed while moving the resist layer surface as in the case of spin drying, for example, the effect (b) may not be sufficiently obtained. Therefore, it is desirable to dry the surface side of the resist layer 1 by wiping with compressed air or the like as in the embodiment. (2) Although the g-line is used for the exposure in the embodiment, a certain effect can be obtained by using an i-line having a shorter wavelength. (3) It is desirable that the resist is dried from the surface to 1/5 or more of the resist thickness so that the above-mentioned effect (a) (improvement of light incidence rate) can be favorably obtained. However, if the dried layer is too thick, the effect (ii) (the generation of the dissolved component of the developer due to the combination with moisture) cannot be obtained satisfactorily.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state in which a resist layer is formed on a semiconductor substrate in an example.

FIG. 2 is a cross-sectional view showing a state in which a hardly soluble portion is provided in the resist layer of FIG.

FIG. 3 is a sectional view showing the principle of an apparatus for drying a resist layer.

FIG. 4 is a sectional view showing an exposure state of a resist layer.

FIG. 5 is a sectional view showing a state after development of a resist layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Resist layer 1b Insoluble part 2 Semiconductor substrate 4 Compressed air cylinder

Claims (4)

(57) [Claims] A first step of forming a positive resist layer containing a naphthoquinonediazide-based substance and a phenolic resin on a main surface of a substrate; and A second step of forming a portion formed by combining the naphthoquinonediazide-based material and the phenolic resin on the surface side of the positive resist layer; and not drying or weakly drying the portion of the positive resist layer on the substrate side. is, the positive-type surface-side portion of the positive type resist layer was strongly dried than the portion of the substrate side
A layer having a relatively high moisture content in the resist layer on the substrate side
Is formed on the surface of the positive resist layer.
A third step of forming a layer having a low water content, a fourth step of selectively exposing a predetermined area of the positive resist layer using a mask, and a step of developing the positive resist layer. Selectively removing the predetermined region of the positive resist layer. 2. The method for forming a resist pattern according to claim 1, wherein the drying of the surface side of the positive resist layer is performed by wiping compressed air or gas. 3. The method for forming a resist pattern according to claim 2, wherein the wiping of the compressed air or gas is performed from a surface of the substrate opposite to a surface on which the resist layer is formed. 4. The formation of a resist pattern according to claim 1, further comprising a step of performing a heat treatment on the resist layer between the third step and the fourth step. Method.