JPH02149851A - Formation of resist pattern - Google Patents

Abstract

PURPOSE:To form a resist pattern providing semiconductor circuit, etc. with improved yield and shortened working time by exposing a surface of a resist material layer to hexamethyl disilazane vapor in a heating stage for forming a resist layer forming simultaneously a resist layer and a zone for enhancing a contrast which has been formed on the surface of the resist layer. CONSTITUTION:A resist material layer 23 is coated on a substrate 11 to be worked and the surface of the resist material layer 23 is exposed to hexamethyl disilazane (b) vapor and heated at the same time. Thus, a resist layer 27 and a zone 25 for enhancing a contrast are formed simultaneously on the surface of the resist layer 27. It is preferred that the resist material layer 23 is constituted of a resinous material contg. phenolic OH groups. Thus, a yield of of semiconductor integrated circuit, etc., is improved, and the working time is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to photolithography technology in the manufacture of semiconductor integrated circuits, etc., and in particular to contrast enhanced lithography (CHtrastEnhancement lithography).
d Lithography (CEL) method to form resist patterns.

(Prior art) As the density of semiconductor integrated circuits increases, the minimum pattern dimensions of circuits to be integrated are becoming increasingly finer. There is a growing demand for technology to form fine resist patterns with high precision.

As is well known, reduction design type exposure snowmaking is suitable for forming resist patterns with high resolution, and 0.5
(um) or less fine pattern formation is possible. If the wavelength of the light used for exposure is λ, and the numerical aperture of the lens system provided in the apparatus is NA, then the resolution line width corresponding to the resolution of this apparatus is expressed as R=in/NA. As can be understood from this equation, in order to reduce the resolution line width, either the wavelength λ can be decreased or the numerical aperture NA of the lens system can be increased. Among these, when increasing the numerical aperture, The depth of focus of the lens system becomes shallow, reducing the focus margin.

Therefore, the CEL method is known as a technique for improving the above-mentioned disadvantages related to the depth of focus using a resist process.

The conventional CEL method will be explained below with reference to the drawings.

FIGS. 2(A) to 2(E) are explanatory diagrams showing each step in a schematic cross section to explain the conventional technology.

First, as shown in FIG. 2(A), a resist material layer 13 to be patterned is applied to the surface of the substrate 11 to be processed.

Accordingly, the solvent contained in the resist material layer 13 is removed,
However, the resin contained in the layer 13 and the substrate 11 to be processed
In order to improve the adhesion with the above-mentioned solvent, heating is performed at a temperature of, for example, about 60 to +20 ('C), depending on the boiling point of the above-mentioned solvent, to form a resist layer 15 as shown in FIG. 2(B).

Next, as shown in FIG. 2(C), a contrast enhancement layer 17 is coated on the surface of the resist layer 15.

After this, exposure is carried out, but usually the contrast enhancement layer 1
7 is a material (referred to as a photo-erasable dye) that has a large absorption at the exposure wavelength before exposure, but as the exposure light is irradiated, the absorption gradually decreases and the transmittance for the light increases. ).

Therefore, as shown in FIG. 2 (CD), when light (indicated by a series of arrows with the symbol a in the figure) passes through the photomask 19, due to the diffraction and focusing effects of the light,
The light reaches the portion of the photomask 19 that is in the shadow with respect to the light source. Here, by using the above-mentioned photomask 19, the above-mentioned photobleachable dye is decolored in the portions of the contrast enhancement layer 17 that are hit by light, and the exposed portions 17a are
Therefore, a portion where the dose of light is relatively small is formed as an unexposed portion +7b. In this way, resist layer 1
The contrast enhancement layer 17 formed on the surface of 5 becomes substantially transparent in the exposed portion 17a, and contrast is formed between the exposed portion 17a and the unexposed portion +7b.

Roughly speaking, as can be understood from FIG. 2(D), the contrast of the light passing through the contrast enhancement layer 17 described above is enhanced compared to when exposure is performed without providing the contrast enhancement layer 17. Exposed portion 1 of resist layer 15
The contrast between 5a and the unexposed portion +5b is increased, and even when the depth of focus is shallow, selective exposure can be performed.

Subsequently, through a development process, a sharp resist pattern 21 can be formed, for example, as shown in FIG. 2(E).

Various kinds of decolorizing dyes are known to be used in the QCEL method, but the literature: “Journal
Of Vacuum 5science Technology
oc+y (Journal of Vacuum Science and Technology)” (85(1), pp. 439-442, 1987) describes the trimethylsilyl group ((C)l
s) 3si-) and those using diazonium salts have been disclosed.

Among these, as a material for a contrast enhancement layer using a trimethylsilyl group, a trimethylsilyl group is bonded to a cresol novolac resin, and 2 is used as a photosensitizer.
-Diazonaphthoquinone-5-sulfonyl group-introduced l
i'Si-LMR-30Jl (manufactured by Fuji Pharmaceutical Co., Ltd.) is used. This material has photosensitivity in the near-ultraviolet region, for example, 9 rays (wavelength 436
(nm)) or i-line (wavelength: 365 (nm)) is used for exposure.

(Problems to be Solved by the Invention) However, in the conventional CEL method described above, after forming a resist layer by heat-treating a resist material, it is necessary to further apply a contrast enhancement layer. As a result, the number of man-hours is increased compared to a normal resist process, resulting in lower yields and increased working time when manufacturing semiconductor integrated circuits and the like.

In view of the above-mentioned conventional problems, an object of the present invention is to provide a resist pattern forming method that can implement the CEL method, which can realize fine resist patterns, with the same number of steps as a normal resist process. .

(Means for Solving the Problems) In order to achieve this object, according to the resist pattern forming method of the present invention, after forming a resist material layer on the surface of a substrate to be processed, the resist material layer is subjected to heat treatment. When forming a resist layer by exposing and developing the resist layer to form a resist pattern, a resist material layer is formed on the above-mentioned substrate to be processed. The coating process and the surface of this resist material layer are coated with hexamethyldisilazane (
SizNH(CH3)e) vapor exposure and heat treatment to form a resist layer and a contrast-enhancing region in a surface portion of the resist layer.

Further, in carrying out the present invention, it is preferable that the resist material layer described above is made of a material containing a phenolic hydroxyl group.

In general, in carrying out the present invention, the above-mentioned resin material containing a phenolic hydroxyl group has a structure in which a part of the phenolic hydroxyl group of a novolac resin synthesized from cresol and formaldehyde is replaced with naphthoquinonediazide sulfonic acid. is suitable.

(Function) According to the structure of the method for forming a resist pattern of the present invention, the process of forming a resist layer by heating the resist material layer, which is performed in the conventional resist process; ■ forming a contrast enhancement layer on the surface of the resist layer Instead of the two steps of coating and forming, during the heat treatment shown as ■,
The surface of the resist material layer is exposed to hexamethyldisilazane (hereinafter sometimes referred to as HMDS) vapor, and a resist layer and a contrast enhancement region formed on the surface portion of the resist layer are simultaneously formed. ing. By allowing HMDS to coexist with the resist material during this heat treatment, trimethylsilyl groups can be introduced into the material.

Therefore, it is possible to eliminate the conventional step of applying a contrast enhancement layer, and moreover, it is possible to form a contrast enhancement region during heat treatment for the purpose of forming a resist layer.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following examples, specific conditions will be explained by way of example in order to facilitate understanding of the present invention, but it should be understood that the present invention is not limited only to these exemplified conditions.

In addition, although the sources of some of the chemicals used in the following examples are omitted, they are all chemically pure and easily available.

Inu 11 Gai 1 First, an example of the steps of the method according to the present invention will be described as Example 1 with reference to the drawings.

FIGS. 1A to 1D are explanatory diagrams showing schematic cross-sections of the substrate, similar to FIGS. 2A to 2E, for explaining the first embodiment.

First, as shown in FIG. 1A, a resist material layer 23 is applied to the surface of a substrate 11 to be processed made of silicon, for example.

Here, the procedure for preparing the resist material used in Example 1 will be explained.

First, the naphthoquinone diazitosulfonic acid ester of cresol novolac resin, lrLM-υv'
(manufactured by Fuji Pharmaceutical Co., Ltd.) 4 (9) is dissolved in methyl cellosolve acetate 1o (9), which is a solvent. In due course,
A resist material is obtained by filtering through a membrane filter having a pore size of 0.2 (um).

When applying such a resist material to the surface of the substrate 11 to be processed, a spin code method is used to apply the resist material to the surface of the substrate 11 to be processed.
A resist material layer 23 was formed with a film thickness of n).

Next, the substrate 11 to be processed in the above-mentioned state is placed on a hot plate and exposed to HMDS vapor for approximately 70
As shown in FIG. 1(B), the resist layer 27 formed by evaporation of the solvent and the above-mentioned IMDs are heat-treated for 1 minute at the temperature of C).
The vapor exposure results in a contrast-enhancing region 25 formed in the surface portion of the resist layer 27 (indicated by a series of arrows bi in the figure).

Here, we will explain the formation of contrast-enhancing regions.
As is well known, FLM Sun-UV,! In the resol novolak resin like I, a part of the phenolic hydroxyl group is substituted by naphthoquinonediazide sulfonic acid, and the remaining phenolic hydroxyl group has high reactivity with the trimethylsilyl group derived from HMDS, such a reaction is , which proceeds easily by heat treatment of the resist material to produce a contrast-enhancing material similar to the aforementioned [i'Si-LMR-30JI.

Therefore, as described with reference to FIGS. 2A to 2C, there is no need to heat-treat the resist material layer to form a resist layer and then apply a contrast enhancement layer.

Thereafter, as shown in FIG. 1C, exposure is performed in the same manner as in the conventional technique, and the above-mentioned contrast enhancement region 25 is made into the exposed portion 25a or the unexposed portion 25b, and the resist layer 271Fr! 1 light portion 27a or unexposed portion 27b. Note that in this embodiment, the contrast enhancement area 25
and the above-mentioned resist layer 27 made of FLM
A reduction projection exposure apparatus (numerical aperture 0.
35)! The dose amount was 250 (mJ/cm2).

Thereafter, heat treatment was performed at +10 ('C), development was performed by immersing in monochlorobenzene for 30 seconds, and rinsing was performed for 10 seconds using xylene. In this manner, a resist pattern 29 as shown in FIG. 1(D) was obtained.

Here, in the exposure process explained with reference to FIG. 1(C), the distance M from the tip of the lens provided in the reduction projection exposure apparatus to the surface of the contrast enhancement area is varied, and the lines and spaces are A resist pattern was formed using a 0.7 (um) photomask, and the pattern shape was observed using an electron microscope. As a result, even if the above-mentioned distance was set to a maximum of 4 (um), the cross-sectional shape of the resist pattern was rectangular, and it was possible to form a good resist pattern.

For comparison with Example 1, a contrast enhancement layer was formed by coating as in the past, and a resist pattern was formed in the same manner as described above. The width of the above-mentioned distance) was a maximum of 4 (μm), and the sensitivity was equivalent to that of the above-mentioned Example]. Roughly speaking, when the resist pattern was formed without applying the CEL method, the maximum focus range was 2 (urn).

On the other hand, when a resist pattern was formed using a roughly fine photomask by applying the method of the present invention, 0.
It was possible to achieve a line and space of 55 (Llm), and also to resolve a hole pattern with a diameter of 0.6 (μm).

In addition, in this embodiment, as the resist material layer 23, diazonaphthoquinone in the exposed portion 27a of the resist layer 27 is released by exposure to light, and the difference in polarity between the diazonaphthoquinone and the unexposed portion 27t of the resist layer 27 is utilized. Ii' L M R-UV, which can be developed with a low polarity developer. This material is trimethylsilylated using 1 and used as the contrast enhancement region 25. Because of this, the unexposed area 2 mentioned above
When removing (developing) 71) with a low polar developer, the exposed portion 25a and unexposed portion 25b of the trimethylsilylated contrast enhancement region 25 can be removed at the same time, which is suitable for reducing the number of steps.

Dog] U property λ Next, in Example 2, the relationship between the film thickness of the contrast enhancement region and the processing conditions with hexamethyldisilazane will be explained.

In this Example 2, the resist material layer 2 is spin-coated in advance.
A resist pattern was formed under the same conditions as in Example 1, except that 3 was set to 1.2 (um) and the entire surface was exposed at a dose of 10100 (/am2).

To explain in detail, the above-mentioned resist material is applied to the surface of the substrate to be processed 11 made of silicon! The resist material layer 23 is formed by spin coating to a film thickness of 1.2 (un).

Next, place the substrate 11 to be processed in the above-mentioned state on a hot plate! and while exposed to HMDS vapor, about 70 ("
Heat treatment is performed for 1 minute at a temperature of C) to form a resist layer 27 and a contrast enhancement region 25.

Next, after exposing the entire surface without using a photomask at a dose of 10100 (/am2), +10 ("C
), followed by development and rinsing under the same conditions as in Example 1 to obtain a measurement sample.

After this development, an optical film thickness measuring device (
Using Screen A (manufactured by Dainippon Screen Mfg., trade name),
The film thickness of the resist remaining on the surface of the substrate 11 to be processed was measured and found to be approximately 1.0 (um).

For comparison, when a resist was formed using the same procedure as described above without performing HMDS vapor treatment, the film thickness of the resist remaining on the surface of the processed substrate 11 was approximately 1.15 C.
μm) or more.

As can be understood from this result, under the coexistence of HMDS,
It can be seen that when heat treated at 70"C for 1 minute, a contrast enhancement area of at least 0.15 um can be formed.

Although the embodiments of the present invention have been described in detail above, it is clear that the present invention is not limited only to the embodiments described above.

In the above-described embodiments, specific conditions such as temperature conditions of heat treatment, time conditions of heat treatment, resist material, and other conditions were exemplified and explained in forming the contrast-enhancing region. However, the present invention is not limited to these conditions, but can achieve a desired film thickness by setting the heat treatment temperature and time depending on the resist material that can be trimethylsilylated in the coexistence of HMDS. By forming a contrast-enhancing region, it is possible to expect the same effects as in the above-described embodiments.

It is clear that these materials, numerical conditions, arrangement relationships, and other conditions may be subjected to any suitable design changes and modifications within the scope of the purpose of the present invention.

(Effects of the Invention) As is clear from the above description, according to the resist pattern forming method of the present invention, the surface of the resist material layer is heated with hexamethyldisilazane vapor during the heat treatment for the purpose of forming the resist layer. to simultaneously form a resist layer and a contrast-enhancing region formed on a surface portion of the resist layer.

Therefore, there is no need to provide a separate coating process for a contrast enhancement layer.

Therefore, by applying this invention, it becomes possible to implement the CEL method, which can realize fine resist patterns, with the same number of man-hours as a normal resist process, thereby improving the yield and manufacturing work of semiconductor integrated circuits, etc. Time can be shortened.

[Brief explanation of the drawing]

FIGS. 1(A) to (D) are explanatory diagrams showing schematic cross sections for each main process of resist pattern formation in order to explain the present invention in detail, and FIGS. 2(A) to (E) FIG. 1 is an explanatory diagram similar to FIGS. 1A to 1D for explaining the prior art. DESCRIPTION OF SYMBOLS 11...Substrate to be processed, 23...Resist material layer 25...Contrast enhancement area 25a...Exposed portion 2 (of the contrast enhancement area)
5b...Unexposed part 2 (of the contrast enhancement area)
7...Resist layer 27a...Exposed portion 27b (of the resist layer)...
- Unexposed portion (of the resist layer) 29...Resist pattern a...Light b used for exposure...Hexamethyldisilazane.

Claims (3)

[Claims] (1) After forming a resist material layer on the surface of the substrate to be processed, heat-treating the resist material layer to form a resist layer, and exposing and developing the resist layer to form a resist pattern. a step of applying the resist material layer to the substrate to be processed; and a step of coating the surface of the resist material layer with hexamethyldisilazane (
Si_2NH(CH_3)_6) A method for forming a resist pattern, the method comprising: exposing the resist layer to Si_2NH(CH_3)_6) vapor and performing a heat treatment to form a contrast-enhancing region in the resist layer and a surface portion of the resist layer. (2) A method for forming a resist pattern, wherein the resist material layer according to claim 1 is made of a resin material containing a phenolic hydroxyl group. (3) The resin material containing a phenolic hydroxyl group according to claim 2 has a structure in which a part of the phenolic hydroxyl group of a novolac resin synthesized from cresol and formaldehyde is replaced with naphthoquinonediazide sulfonic acid. A method for forming a resist pattern.