JPH06267838A - Method of forming resist pattern - Google Patents

Abstract

PURPOSE:To prevent the influence of a resist surface layer which is hard to dissolve, and form a resist pattern highly conformable to a designed pattern, by adding a process exposing the resist surface to an acid atmosphere after exposure to light and before baking, and dissolving the whole resist surface as far as a specified depth in a developing process. CONSTITUTION:In order to supplement acid which is insufficient in the vicinity of a resist surface of a silicon substrate coated with a resist layer 2, the laver is spin-coated with solution wherein acetic acid is diluted to 10% with pure water, thereby obtaining an acid supplement layer 3. Then selective exposure to light is performed by using KrF excimer layer 4, arud acid 5 is generated. After the exposure to light, baking is performed at 110 deg.C for 2 minutes. Hence the acid supplement layer 3 on the resist surface, and high-molecular dissolution inhibiter THP-M in the part of the resist where acid is selectively generated are decomposed, and dissolution inhibiting effect is reduced. Then a developing process is performed. The acid supplement layer 3 on the resist surface is dissolved, and a resist pattern 7 can be obtained.

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 pattern on a wafer or a photomask, for example, faithfully to a design dimension, using a photosensitive resist.

[0002]

2. Description of the Related Art In recent years, as the processing size has become finer,
Resist materials have also made great progress. Among them, a resist called a chemically amplified resist generates an acid at the time of exposure and utilizes the catalytic action of this acid to accelerate the reaction of the resist. (Reference: Resist material / process technology, 1
04-112, Technical Information Institute, 1991, Tokyo) This chemically amplified resist has the characteristic of having higher sensitivity than conventional resists, but the problem is that it is limited to the problems of positive resists. The formation of the surface insolubilized layer may be mentioned. Here, a conventional process in which a chemically amplified positive resist is used and development is performed will be described with reference to FIG.

On the silicon substrate 1, tetrahydropyranylated poly (p-vinylphenol) (THP-M), which is a polymer dissolution inhibitor, and tri (methanesulfonyloxy) benzene (MeSB), which is an acid generator, A chemically amplified positive resist consisting of three components of novolac resin is used as a resist.
The resist layer 2 was formed by spin coating to a thickness of 35 μm and prebaking at 125 ° C. for 2 minutes (FIG. 6).
(A)).

Next, 50 KrF excimer laser 4 is used.
The resist was exposed selectively with an irradiation amount of mJ / cm2 to generate an acid in the exposed portion of the resist (Fig. 6 (b)).

After that, a post-exposure bake is carried out at 110 ° C. for 2 minutes to decompose the polymer dissolution inhibitor THP-M in the portion where the acid is selectively generated inside the resist to eliminate the dissolution inhibiting effect (FIG. 6). (C)).

Further, the resist pattern 7 was formed by immersing in a 2.38% aqueous solution of tetramethylammonium hydroxide for 2 minutes and developing it. As a result of observing the pattern cross section obtained at this time, the result is as follows. That is, when the surface hardly-solubilized layer 17 is formed on the resist surface, a difference in dissolution rate occurs between the surface hardly-solubilized layer and the layer thereunder, and the pattern upper part is solved into a so-called T-top shape as shown in FIG. 6D. I will be imaged. For this reason, it is difficult to form the pattern faithfully to the design size because the pattern size varies greatly.

One of the reasons why the surface insolubilized layer is formed is considered to be the influence of the atmosphere on the resist surface. For example, if the resist after pre-baking is exposed in a certain atmosphere, baked after exposure, and developed, a portion that is difficult to dissolve is formed at a certain depth from the resist surface, and only the portion below it is patterned. . It is considered that the cause of this is that the substance in the atmosphere in contact with the resist surface adheres and diffuses to cancel out the acid generated during exposure, leaving only the resist surface undissolved. (Takamichi, 5 others, Proceedings of 39th Joint Lecture on Applied Physics, 1992, Spring, No
(Page 2, 576) In addition, the acid generator in the vicinity of the surface evaporates out of the resist during the process of coating and developing the resist, so that the acid in the resist film has a concentration distribution in the depth direction of the resist. Will end up.

[0008]

As a method for preventing the formation of the surface insolubilized layer, a method has been reported in which a cover film is applied on the applied resist surface to block the influence of the atmosphere on the resist surface. (Shandong, 4 others, Proceedings of 53rd Annual Meeting of the Japan Society of Applied Physics, 1992, Autumn, No
(Page 2, 504) By using this method, it was possible to considerably suppress the generation of the surface insoluble layer. However, it was not possible to completely eliminate the formation of the surface hardly soluble layer.

An object of the present invention is to provide a method of forming a resist pattern faithful to a design pattern by preventing the influence of a resist surface insolubilizing layer, which has been a problem in conventional chemically amplified resists.

[0010]

The object of the present invention is to provide a chemically amplified positive type resist processing method, which comprises applying a resist on a substrate to be processed, pre-baking, exposing, post-exposure baking, and developing. This is achieved by adding a step of exposing the resist surface to an acidic atmosphere before the treatment and dissolving the entire surface of the resist to a certain depth from the surface in the developing step. The step of exposing the resist to an acidic atmosphere may be any time between application of the resist and post-exposure bake processing, and several possible steps can be shown. For example, it can be exposed to an acidic atmosphere between the pre-baking step and the exposure step after applying the resist. Alternatively, it may be added immediately after the post-exposure bake.

[0011]

In the above-mentioned step of exposing to the acidic atmosphere, the acid can be diffused from the resist surface to replenish the deficient acid in the vicinity of the resist surface. As a result, in the case of a positive type resist, the resist surface is easily dissolved in the developing solution. Since the effect of the step of exposing the resist to the acidic atmosphere is limited to about 0.025 μm to 0.1 μm from the surface, acid is generated only in the exposed portion inside the resist, and only the exposed portion is exposed to the developing solution in the post-exposure bake step. In contrast, it becomes easier to dissolve. As a result, it is possible to prevent the formation of the surface insolubilized layer, which has been a problem with the conventional chemically amplified positive resist, and to form a highly accurate resist pattern.

[0012]

EXAMPLES The present invention will be described in detail below with reference to examples, but the following examples do not limit the scope of the present invention.

Example 1 A case in which the present invention is applied to pattern formation using a single-layer resist structure will be described (FIG. 1).

First, tetrahydropyranylated poly (p-vinylphenol) (THP-M), which is a polymer dissolution inhibitor, and tri (methanesulfonyloxy) benzene (MeSB), which is an acid generator, are formed on a silicon substrate 1. And a chemically amplified positive resist consisting of three components of novolac resin were spin-coated to a thickness of 0.35 μm, and prebaked at 125 ° C. for 2 minutes to form a resist layer 2 (FIG. 1).
(A)).

Next, the silicon substrate 1 coated with the resist layer 2 is spin-coated on the resist layer with a solution of acetic acid diluted to 10% with pure water for the purpose of supplementing the deficient acid in the vicinity of the resist surface. By doing so, an acid replenishing layer 3 was obtained (FIG. 1 (b)).

Then, the KrF excimer laser 4 is turned on 50 times.
Exposure was selectively performed at a dose of mJ / cm2 to generate acid 5 in the exposed portion inside the resist (Fig. 1).
(C)).

Next, post-exposure bake is carried out at 110 ° C. for 2 minutes, and the acid replenishment layer 3 on the resist surface and the polymer dissolution inhibitor THP-M in the resist inside the portion where the acid is selectively generated.
Was dissolved to eliminate the dissolution inhibiting effect (Fig. 1 (d)).

Further, the sample was immersed in a 2.38% aqueous solution of tetramethylammonium hydroxide for 2 minutes for development processing. At this time, the acid replenishment layer 3 on the resist surface was dissolved in a developing solution to obtain a resist pattern 7 formed under the uniform dissolution layer 8 (FIG. 1 (e)).

FIG. 2 is a graph comparing the dissolution rates when the acid replenishing layer 3 is formed on the resist surface of the first embodiment and when the surface-hardened layer 17 is formed by the conventional exposure method. . It can be seen from FIG. 2 that, in the case of the conventional exposure method, the surface-insolubilized layer 17 is formed because the acid on the resist surface is deficient, and therefore the resist is not immediately dissolved even when the development is started. Therefore, it took 3 minutes and 30 seconds until the resist was dissolved. On the other hand, in Example 1, it can be seen that the acid replenishment layer 3 is present on the resist surface, so that the dissolution starts immediately after the development. From this, it can be seen that the difference 9 in the resist dissolution process in FIG. 2 is caused by the formation of the surface insolubilized layer 17. In Example 1, the acid replenishing layer 3 on the surface of the resist was also dissolved. Therefore, when the amount of residual resist film after development was measured, it was found that the amount was reduced by 0.05 μm according to this example. As described above, the surface insolubilized layer was not formed in the resist pattern formed in this example.

Embodiment 2 FIGS. 3 and 4 show an example in which the present invention is applied to manufacture of a phase shift mask. Furthermore, an example is shown in which the method of providing the acid replenishing layer 3 on the resist surface and the method of exposure are different.

The phase shift method is a method for improving resolution and depth of focus by inverting the phase of light called a shifter by 180 ° at every other opening of the mask, which is an essential process for high integration of semiconductors in the future. Is. The principle of the phase shift method and the mask manufacturing method are described in, for example, Electrochemistry and Industrial Physics Vol. 58, No. Pages 4,330 to 3
Page 35 (1990) Hasegawa et al., “Subμm Lithography by Phase Shift Method”. In this method, since a transparent insulator is used as the shifter material, there arises a problem of a substrate charging phenomenon which is not a problem in the conventional mask making.

The structure shown in FIG. 3A shows the structure of a normal chromium mask substrate. It can be seen from FIG. 3A that the metallic chromium layer 11 is deposited on the quartz glass substrate 10.

Tetrahydropyranylated poly (p-vinylphenol) (THP-M), which is a polymer dissolution inhibitor, and tri (methanesulfonyloxy) benzene (MeSB), which is an acid generator, are formed on the chromium mask substrate. A chemically amplified positive resist consisting of three components of novolac resin was spin-coated to a thickness of 0.4 μm, and prebaked at 125 ° C. for 5 minutes to form a resist layer 2. The baking time was set to 2 to 5 minutes in consideration of the heat capacity of the substrate. Thereafter, for the purpose of supplementing the deficient acid in the vicinity of the surface of the resist layer 2, the step of exposing the resist surface to an acidic atmosphere is spin-coated with an Espacer 100 (trade name of Showa Denko KK) 13 containing a water-soluble organic acid. It was done by Therefore, the acid replenishment layer 3 was formed on the resist surface. Since the espacer 100 is also a conductive material, an effect as an antistatic film can be expected. The coating film thickness at this time was 0.05 μm (FIG. 3B).

First, the electron beam 14 was selectively exposed at a dose of 2.0 μC / cm 2 to generate an acid 5 in the exposed portion inside the resist (FIG. 3C).

Next, the espacer 10013 was washed with running water for 1 minute, and then post-exposure baked at 110 ° C. for 5 minutes to generate an acid replenishing layer 3 on the resist surface and selectively generate an acid inside the resist. Partial polymer dissolution inhibitor THP-
M was decomposed to eliminate the dissolution inhibiting effect (Fig. 3 (d)).

The above sample was immersed in a 2.38% aqueous solution of tetramethylammonium hydroxide for 2 minutes for development processing. At this time, the acid replenishment layer 3 on the resist surface was dissolved in a developing solution to obtain a resist pattern 7 formed under the uniform dissolution layer 8 (FIG. 3 (e)).

The metal chromium layer 11 was selectively wet-etched using the resist pattern 7 of the sample as a mask (FIG. 3 (f)).

Metal chrome layer 11 obtained by the above process
A phase shifter material 12 (here, a silicon oxide film) is deposited to a thickness of 0.4 μm on the entire upper surface. In this structure, since the metallic chromium layer is present separately on the quartz substrate, a substrate charging phenomenon occurs during electron beam irradiation (FIG. 3 (g)).

On the phase shifter material 12, the chemically amplified positive resist is spin-coated to a thickness of 0.4 μm,
Prebaking treatment was carried out at 125 ° C. for 5 minutes to obtain a resist layer 2. For the purpose of replenishing the deficient acid near the surface of the resist layer 2 and for the effect as an antistatic film at the time of electron beam irradiation, the above-mentioned espacer 10013 was spin-coated. Therefore, the espacer 100 (antistatic film) 13 was formed on the resist, and the acid replenishment layer 3 was formed near the resist surface. (FIG. 4 (a)).

An electron beam 14 was selectively exposed to the region where the shifter material 12 was to be etched at a dose of 2.0 μC / cm 2 to generate an acid 5 in the exposed portion inside the resist (FIG. 4 ( b)).

Put the espacer 10013 into running water 1
After washing with water for 1 minute and removal, baking is performed at 110 ° C. for 5 minutes, and the acid replenishment layer 3 on the resist surface and the polymer dissolution inhibitor THP inside the resist where acid is selectively generated.
-M was decomposed to eliminate the dissolution inhibiting effect (Fig. 4).
(C)).

Next, the sample was immersed in a 2.38% aqueous solution of tetramethylammonium hydroxide for 2 minutes for development processing. At this time, the acid replenishment layer 3 on the resist surface was dissolved in a developing solution to obtain a resist pattern 7 formed under the uniform dissolution layer 8 (FIG. 4 (d)).

Using the resist pattern 7 of the sample as a mask, the phase shifter material 12 was selectively wet-etched to obtain a required pattern of the phase shifter 15 (FIG. 4 (e)).

FIG. 5 shows the relationship between the resist residual film amount after development and the processing conditions when the processing conditions in each step of the second embodiment were changed. FIG. 5A shows the prebaking temperature dependency of the resist residual film amount in the unexposed portion after development when the post-exposure bake temperature is 120 ° C. for a resist coating film thickness of 0.35 μm, and FIG. 2) shows the post-exposure bake temperature dependence of the resist residual film amount in the unexposed portion after development when the resist coating film thickness is 0.37 μm and the pre-bake temperature is 125 ° C. for 2 minutes. In FIG. 5A, the residual film amount increases as the prebake temperature increases. Figure 5
As shown in (b), it can be seen that the film thickness is reduced by about 0.025 μm when the baking condition adopted in this example is used. Further, the amount of film loss when using the Espacer 10013 was dependent on the baking temperature from the experimental results and could be controlled with good reproducibility. As described above, the surface hardly-solubilized layer 17 was not formed on the resist pattern 7 formed in this example. In addition, the isolated metallic chrome pattern 11 on the quartz substrate 10
Even if the electron beam drawing was performed on the above, the positional displacement of the pattern due to the charging phenomenon did not occur.

In this embodiment, an example was given in which the step of exposing the resist surface to an acidic atmosphere was performed between the pre-baking step and the exposure step after resist application. However, in the step of exposing to an acidic atmosphere, the resist is applied. Any time between after and after the post-exposure bake treatment can indicate some possible steps. For example, the acid replenishment layer 3 can be formed by leaving the resist surface in an acid vapor atmosphere between the pre-baking step and the exposure step after applying the resist. Alternatively, when the espacer 10013 is used, it is possible to apply the espacer 10013 on the resist surface after the exposure and before the baking, and then remove the espacer 10013 and perform development processing.

[0036]

As described above, according to the method of forming a resist pattern of the present invention, in addition to the effect of preventing the charging phenomenon of the substrate, the surface insolubilized layer formed when a chemically amplified positive resist is used is formed. By exposing the resist surface to an acidic atmosphere, the resist surface is easily dissolved in the developing solution. From this, by melting the entire surface of the resist to a certain depth from the surface, it is possible to form a highly accurate resist pattern with respect to the design dimension.

In the method of the present invention, (1) acetic acid and Espacer 100 were used as the acidic material, but it is also possible to use one containing other acid instead. (2) In the present invention, the step of exposing the resist surface to an acidic atmosphere is performed prior to the exposure, but it may be applied or removed anywhere between the application of the chemically amplified positive resist and the post-exposure bake. (3) As another usage of the espacer 100, since it is conductive, it can be used as an antistatic film for electron beam drawing. (4) It goes without saying that the method of the present invention can be applied to any lithographic process using a chemically amplified positive type resist.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is a graph illustrating the effect of the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a second embodiment of the present invention.

FIG. 5 is a diagram showing the baking temperature dependency of the residual film amount.

FIG. 6 is an explanatory diagram of a conventional pattern forming method.

[Explanation of Codes] 1 ... Silicon substrate, 2 ... Resist layer, 3
... acid replenishment layer, 4 ... ultraviolet light, 5 ... acid generation region, 6 ... dissolution inhibitor decomposition region,
7 ... Resist pattern, 8 ... Uniform dissolution layer, 9
... Difference in resist dissolution process, 10 ... Quartz glass substrate,
11 ... Metal chromium layer, 12 ... Phase shifter material, 13 ... Espacer 100, 14 ... Electron beam, 15 ... Phase shifter, 16 ... Acid-deficient part, 17 ... Surface Hardly soluble layer.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical indication location G03F 7/38 501 7124-2H 511 7124-2H 7352-4M H01L 21/30 361 G (72) Inventor Shin Okazaki Next 1-280, Higashi Koigokubo, Kokubunji, Tokyo Metropolitan Research Center, Hitachi, Ltd.

Claims (4)

[Claims] 1. A method for processing a chemically amplified positive resist in which a resist is applied on a substrate to be processed, prebaking, exposing, post-exposure baking and developing are performed, and after the step of exposing the resist surface to an acidic atmosphere. A method for forming a resist pattern, which comprises a step of performing a post-exposure bake treatment and dissolving the entire surface of the resist to a certain depth from the surface in the subsequent developing step. 2. The method of forming a resist pattern according to claim 1, wherein the step of exposing the resist surface to an acidic atmosphere is a step of applying an acidic material to the resist surface. . 3. The method for forming a resist pattern according to claim 2, wherein the acidic material is a water-soluble organic acid. 4. The method for forming a resist pattern according to claim 2, wherein the water-soluble organic acid is applied prior to exposure and the acidic material is removed after baking after exposure. Forming method.