JPS62239530A - Formation of pattern - Google Patents

Abstract

PURPOSE:To form a resist pattern effective in processing a substrate with a step difference by a method wherein multilayer exceeding three layers resist process as well as a resist with excellent dryetching resistance as a lower resist are used. CONSTITUTION:A lower layer resist with excellent dryetching resistance is formed on a substrate. First, the lower layer resist is coated with water soluble polymer as an intermediate layer. Second, an upper layer mask with high molecular extinction coefficient and resolution is formed to be exposed to a specified pattern while an upper layer resist film is developed using alkali water solution as a developer to form a positive pattern. Third, the upper layer pattern is exposed using the upper layer resist pattern as a mask to be removed by alkali water solution. Fourth, the intermediate layer is immersed in water to be removed. Finally, the lower resist is immersed in alkali water solution to form a specified pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pattern forming method suitable for microfabrication of semiconductor devices, etc., and more particularly to a pattern forming method using a multilayer structure resist process on a stepped substrate.

[Conventional technology]

PCM by Lin as a processing method for substrates with steps
(Portable Coffiformable
Mask) method is known. This method is applied to the lower layer.
Polymethyl methacrylate that becomes positive under epUV light (
PMMA), and a positive photoresist is used as the upper layer (SPIE, 174).
, 114 (1979)).

However, acrylic polymers such as PMMA have a problem in dry etching resistance. PC after Lin's announcement
Although many pattern forming methods using M have been reported, this problem remains unsolved.

[Problem that the invention seeks to solve]

Currently, photolithography is mainly performed using a reduction projection exposure apparatus. It is extremely difficult to use this exposure apparatus to form a pattern with a high aspect ratio that is close to the resolution limit of these exposure apparatuses with a single resist layer on a stepped substrate.

This is because from the perspective of resist resolution, it is generally said that it is better for the resist l- film to be uniform (coated on a flat substrate) and thinner, but on a stepped plate, it is necessary to cover it. This is because the resist must be applied thickly, resulting in uneven resist film thickness. The PCM method is used to solve these problems, but as mentioned earlier, it uses an acrylate resist such as PMMA for the lower layer, so there is a problem with dry etching resistance when processing the substrate. .

An object of the present invention is to provide a method for forming a resist pattern with high dry etching resistance, which is effective in processing a substrate having steps.

[Means for solving problems]

The above PCM method is a useful pattern forming method if dry etching resistance can be improved.

In other words, if a highly accurate pattern is formed using a reduction projection exposure device on the upper layer resist coated on the flattened surface, and this is used as a deep UV mask, it will become an ideal close-contact short wavelength exposure, and a pattern with a high aspect ratio can be created. You should be able to form one. Therefore, we investigated a pattern formation method that uses a lower resist that is resistant to dry etching.

What is required of the lower resist is that a pattern with high g-image resolution can be formed using light of a wavelength different from the exposure wavelength of the upper resist, preferably short wavelength light, and light of a wavelength sufficiently absorbed by the upper resist.

As a resist that can form a high-resolution pattern with light in the deeρ UV region, there is a mixed resist of an alkali-soluble polymer and an azide compound. This resist can be created by combining an alkali-soluble polymer and an azide compound, or by selecting the exposure wavelength.

Even with a thick resist film, it is possible to expose parts close to the substrate, and a pattern with a high aspect ratio can be obtained. For example, RD-
It was found that 200ON (Hitachi Chemical fR) can avoid absorption of the base polymer by using light around 300 nm and form a pattern with a high aspect ratio.

The alkali-soluble resin that makes up the lower resist layer is as follows:
Polyvinylphenol, halide of polyvinylphenol, novolak resin, halide of novolac resin, styrene-maleic anhydride copolymer, cellulose acetate hydrogen phthalate, polyvinyl hydroxybenzoate.

Possible examples include polyhydroxybenzal, styrene-ethyl acrylate-acrylic acid copolymer, methyl methacrylate-methacrylic acid copolymer, and other polymers having carboxyl groups.

As an azide compound, 1, for example, 31 from among the compounds shown in Table 1! can run. Table 1 also shows the maximum absorption wavelength (λ1Ilax) of the azide compound.
When selecting the azide compound, it is preferable to consider the light absorption characteristics of the E layer and the di-s 1-.

First, in order to use the pattern of the resist as a mask, it is necessary to select an azide compound that is sensitive to the wavelength range of light that is sufficiently absorbed by the upper resist. As I will explain next)
Since I selected the material for the Z layer 1 nodist, the bottom weight is 5g! It is desirable that λmax of the asiazide conversion is about 300 nm or less.

When used as a lower resist, the weight ratio of the alkali-soluble polymer to the azide compound is preferably 0.01 to 1:1, more preferably 0.1 to 0.5=1.

Table 1 Azide compounds λmaX 3.3'-diazide diphenyl sulfone 240
nm4.4'-Diazidiphenylmethane 2
56 3.3'-dichloro-4,4'-diazide
258# Diphenylmethane 4.4'-Diazidiphenyl ether 264
/14.4'-Diazidiphenyl disulfide 2
66#4.4'-Diazidiphenyl sulfide
273114.4'-Diazidiphenylsulfone
284#3.3'-Diazidobenzophenone
246#4.4'-Diazidobenzophenone
300/1 On the other hand, the upper layer resist is required to have high resolution and to serve as a mask when exposing the lower layer resist. Regarding resolution.

It is sufficient to use a mixed resist consisting of an alkali-soluble polymer and a photosensitizer (a naphthoquinone diazide compound for positive type, an azide compound for negative type).

However, when these resists are used as they are as upper layer resists, they cannot serve as a sufficient mask for exposing the lower layer resists. That is, when exposing the lower layer resist, the upper layer resist cannot sufficiently absorb light of that wavelength, so that it becomes impossible to form a pattern on the lower layer resist. Therefore, we considered adding a dye to the upper resist layer.

When selecting a dye, it is necessary to select one that sufficiently absorbs light at the wavelength to which the underlying resist is sensitive, has a high molecular pseudolight coefficient, and does not deteriorate the exposure and development characteristics of the resist due to the addition of the dye. It has been found that 2'-hydroxychalcone and 4'-hydroxychalcone are examples of dyes that meet these requirements, and can sufficiently absorb light of 350 nm or less without changing resist performance. This means that light of approximately 350 nm or more is used to form a pattern on the upper resist layer.

When a positive type photoresist is used for the upper resists 1 to 1, the naphthoquinone cyacyto compound is selected from, for example, the compounds represented by the general formula (1) shown in Table 2. As a substituent (R) of the compound represented by this general formula (1),
For example, those shown in Table 2 can be mentioned.

In addition to the quinonediazide compounds shown in Table 2, naphthoquinonediazide compounds used in known photosensitive compositions can also be used, or two or more of these can be used in combination.

When a negative photoresist is used as the upper layer resist, the azide compound can be selected from those having absorption at wavelengths of about 350 nm or more, for example, from the compounds shown in Table 3. In addition to the azide compounds shown in Table 3, azide compounds used in known photosensitive compositions can also be used, and it is also possible to use a mixture of two or more of these.

Table 2 Table 3 Azide compounds Max 4-azidochalcone 337 II m
4-azido-4'-hydroxychalcone 3
38 Cinnamylidene-4-azidoacetophenone
3504-azidocinnamylideneace1-phenone
365 Dimethyl-2-cyclohexen-1-one 3-C4-(p-azidophenyl)-1,3-butadienyl)5,5-dimethyl 368-2
-Cyclohexen-1-one In the present invention, when a positive type photoresist 1- is used as the upper layer, the amount of the naphthoquinone diazide compound 2, represented by the general formula ([), and the alkali-soluble polymer! The It ratio is preferably 0.05 to 1:0.1 to 2:1, and more preferably 0.1 to 0.5:0.2 to 1:1.

In the present invention, when a negative photoresist is used as the upper layer, the amounts of the azide compound 9 dye and the alkali-soluble polymer are in a weight ratio of 0.05 to 1:0. :1-2:1 is preferable, and 0.1-0.5=0.2-1:1
It is more preferable that

” A series of negative resists for the lower layer, -positive resists for the upper layer 1-
Both the resist and the negative type photoresist are alkali-soluble resists, and because they use the same solvent system, it is not possible to apply the single-layer resist directly to the lower resist. It is necessary to separate the two layers. In order to separate these two layers, it is necessary to select a polymer with a solvent system different from that of the upper resist. Polydiene water-soluble polymers and the like are examples of intermediate layer polymers that meet these requirements.

From the viewpoint of coating film formation, water-soluble polymers are preferable, but when the upper layer is developed with an alkaline aqueous solution, they dissolve and disturb the pattern. On the other hand, with polydiene, a boundary layer is formed between the upper resist layer and the lower layer 1/cyst cannot be developed with an alkaline aqueous solution. Therefore, a water-soluble polymer and further polydiene are formed on the lower layer to form the middle layer.
When exposing the lower layer using the 6-1 layer resist as the f1 layer as a mask, it is desirable that the intermediate layer be thin in order to improve the resolving power unless the upper and lower resist layers are mixed. The combined thickness of the two intermediate layers is preferably in the range of 0.1 to 1 μm. Moreover, it is preferable that it is substantially transparent to the wavelength of light that exposes the underlying resist.

Examples of water-soluble polymers include homopolymers such as carboxymethyl cellulose, hydroxymethyl cellulose, gelatin, polyacrylic acid, polyvinyl methyl ether, polyvinyl alcohol, polyvinyl acetal, and polyethylene oxide, copolymers of acrylamide and vinyl alcohol, and maleic acid. - Copolymers such as vinyl methyl ether copolymers, acrylamide and diacetone acrylamide copolymers, etc. are used.

Examples of polyene include polybutadiene.

Polyisoprene, cyclized polyisoprene, poly(2-chlorophtadiene), etc. are used.

It is also possible to form the intermediate layer from a polymer other than those mentioned above, or to form the intermediate layer into a single layer.

[Effect]

As described above, by using a multilayer resist process of three or more layers and by using a resist with high dry etching resistance as the lower layer resist, a resist pattern that is effective for processing a substrate having steps can be obtained.

〔Example〕

Example 1 As a lower layer resist 1-, RD-200ON (manufactured by Hitachi Chemical) was coated on a silicon wafer and then coated at 80° C. for 20 minutes to form a lower layer film. Next, a water-soluble polymer (a copolymer of acrylamide and diacetone acrylamide) as an intermediate layer is applied to a thickness of approximately 0.2 μm, and further cyclized polyisoprene (013C-8 manufactured by Tokyo Ohka Co., Ltd.) is spin-coated to a thickness of approximately 0.2 μm. A 2 μm film was formed.The upper layer resist was 0FPR-
A solution prepared by adding 10 parts by weight of 2'-hydroxychalcone to 100 parts by weight of 5000 (positive type photoresist manufactured by Tokyo Ohka Co., Ltd.) was obtained by simultaneous coating. After exposing this exposed sample in a desired pattern using Hitachi's reduction projection exposure system RAIOIHL, the upper layer was immersed in an alkaline aqueous solution (approximately 1.6% by weight aqueous solution of tetramethylammonium hydroxide) as a developer for 45 seconds. The resist film was developed to obtain a positive pattern. Using this upper resist pattern as a mask, light from an Xa-Hg lamp was exposed through a UV-31 filter. The upper resist layer was removed by immersion in an alkaline aqueous solution (tetramethylammonium hydroxide 2.38 weight percent aqueous solution) for 30 seconds.

Next, the intermediate layer was removed by immersing it in xylene for about 1 minute and then in water for 1 minute. Finally, the lower resist layer was immersed in an alkaline aqueous solution (a 1.19 weight percent aqueous solution of tetramethylammonium hydroxide) for 2 minutes to obtain a pattern. When this sample was scanned and observed using a submicroscope, it was confirmed that lines and spaces with a high aspect ratio of 1 μm were formed.

Example 2 In place of the 2'-hydroxychalcone used in Example 1, 4'-hydroxychalcone was added to 0FPR-5000 to prepare an upper layer resist solution. When a pattern was formed in the same manner as in Example 1, it had a high aspect ratio of 1 μm.
I was able to form patterns of lines and spaces.

Example 3 Instead of the J single layer resist used in Example 1, :3-(4
-(p-azi1phenyl) -1,3butadienyl)
-5,5 dimethyl-2-cyclohexen-1-one 4
1t<w part, 7 parts of 2'-hydroxychalcone, 20 parts by weight of polyvinylphenol, 80 parts by weight of cyclol-xane
It was dissolved in the heavy paper part to make a resist solution. When a pattern was formed in the same manner as in Example 1, a pattern with a high aspect ratio of 1
A pattern of μm lines and spaces could be formed.

[Effects of the Invention J Below] - As explained in detail, the pattern forming method of the present invention is capable of forming a pattern with a high aspect ratio of 7 on a stepped substrate, and the pattern can be easily formed in the subsequent drying process. Resistant to etching.

Therefore, according to the present invention, the drawback that the dry etching resistance of the pattern produced by PCMrA is poor can be solved, and the present invention is of great practical value.

Claims (1)

[Claims] 1. Forming a lower resist film of a resist that can be developed with an alkaline aqueous solution on a predetermined substrate, forming an intermediate layer on top of the lower resist film, and further forming an upper resist film that can be developed with an alkaline aqueous solution, and The intermediate layer is made of a polymer compound in a solvent different from that of the lower and upper resist layers, and a desired pattern is exposed to light on the upper resist layer, developed to reveal it, and is used as a mask to expose the entire surface of the lower resist layer to light. A pattern forming method characterized by exposing the intermediate layer and the upper layer resist to light, and then developing the lower layer resist with an alkaline aqueous solution to form a desired pattern.