JPH0727216B2 - Pattern formation method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a pattern forming method, and more particularly, to a pattern forming method capable of forming a fine pattern with high accuracy even when there is a step on the substrate surface. Regarding the method.

[Background of the Invention]

In recent years, as the scale and density of semiconductor integrated circuits have increased, it has become more and more required to form extremely fine patterns on a substrate with high accuracy. As is well known, when various fine patterns are formed on a substrate, a method generally called photolithography is used. This photolithography can form a good resist pattern having a line width of about 1 μm when a substrate having a smooth and low reflectance is used, but the substrate has irregularities or steps (hereinafter referred to as a single step). 2), the incident light is diffusely reflected at the step portion, so-called halation occurs, and the pattern shape is deteriorated (broken), so that a good resist pattern cannot be formed. Moreover, since the film thickness of the resist film is different between the upper part and the lower part of the substrate step portion, the optical interference state in the resist film is changed, the line is thickened or thinned, and the pattern dimension is changed. A method called a multi-layer resist method has been proposed as one of the methods for solving these problems caused by the steps on the substrate surface and performing good patterning.

In the multi-layer resist method, the steps of the substrate are flattened with a thick organic layer having a high light absorption property, and then a thin resist pattern is formed thereon using a well-known lithographic technique. And the exposed portion of the substrate is etched. Although the thick organic material layer can be etched using the resist pattern as a mask, a thin film having a large dry etching resistance can be interposed between the two, and the thick organic material layer can be etched using this film as a mask. Good.

In the multi-layer resist method, since the step on the substrate surface is flattened by the organic layer having high light absorption, the exposure light passing through the photoresist layer formed thereon is absorbed by the organic layer, so that the substrate surface Phenomena such as halation in the stepped portion of the substrate and light interference in the resist film due to reflection and scattering of light from the substrate can be reduced, and collapse of the pattern shape and dimensional fluctuation can be suppressed.

Conventionally, as an organic layer for flattening the step,
A method of adding a positive resist of novolak resin or a dye having a good light absorption property (Japanese Patent Laid-Open No. 172736/1982) has been proposed.

However, in order to absorb the light of 436 nm or 405 nm, which is the exposure wavelength of the reduction projection exposure method, by using the above-mentioned novolak resin-based positive resist as the lower layer material, a high temperature bake of 200 ° C. or higher is required. The higher the baking temperature, the stronger the absorption of the exposure light. However, when a high temperature bake of 200 ° C or more is applied, carbonization of the surface begins, the adhesion with the upper layer becomes insufficient, or the detection light for alignment having a longer wavelength is absorbed. There was a flaw.

On the other hand, an attempt to use a positive resist containing a dye as an exposure light absorbing lower layer material has been reported.
chel M.O'Toole et al., “Linewidth Control in Project
ion Lithography Using a Multilayer Resist Process "
IEEE Electron Device, ED-28, 1405 (1981)
As can be seen in Fig. 3, in order to prevent dye sublimation or decomposition, the baking temperature can be raised up to about 160 ° C at most, so that the insolubilization of the lower layer film is insufficient and the lower layer film is dissolved when the upper layer photoresist is applied. In order to make it difficult to form a multilayer structure and to improve the resistance of the resist in the etching process, a spin-on glass (SO
G)] is used, since the baking temperature of the lower layer is low, gas is released from the lower layer when the intermediate SOG layer is baked, which causes cracks in the SOG layer, and There was a problem that it was difficult to form.

In order to solve these problems, the present inventors previously proposed a method of adding an aromatic azide compound to the lower organic layer of a multi-layer resist and patterning it (Japanese Patent Application No. 59-191448). In order to form a pattern with high accuracy, an even better method is desired.

[Object of the Invention]

The object of the present invention is to eliminate the above-mentioned drawbacks of the conventional multi-layer resist method and to have a large absorptivity for light used for exposure, and a material having a low absorptivity of light for alignment as a lower organic material layer in the multi-layer resist method. The purpose of the present invention is to provide a method for forming a fine pattern with extremely high dimensional accuracy on a substrate having irregularities or steps.

[Outline of Invention]

In order to achieve the above-mentioned object, the present invention contains an aromatic sulfonyl azide compound in the lower organic layer, and has a large light absorptivity to be used for exposure by heating or whole surface exposure treatment (small light transmittance). ), And a lower organic material layer that is changed to a substance having a small light absorption (high light transmittance) for alignment light, and the main point is to perform patterning by a multi-layer resist method. .

The present inventors, as a result of searching various light-absorbing compounds,
Aromatic sulfonyl azide compounds are decomposed in various polymer compound (polymer) films by heating (baking) or overall exposure treatment, react with the polymer, and are non-volatile. It was found that, unlike the compound, the spectrum hardly changed due to decomposition. Then, they have found that this can be utilized as a light-absorbing lower organic layer in a multilayer resist process, and have completed the present invention.

The present invention, an organic material layer is formed on a substrate having a step, and a photoresist layer is formed thereon, or an intermediate layer is formed between the organic material layer and the resist layer,
A desired resist pattern is formed on the resist layer by a known exposure / phenomenon treatment, and the resist pattern is transferred to the lower organic material layer to form a desired pattern on the substrate. In the resist method, an aromatic sulfonyl azide compound is contained in the organic material layer formed on the substrate, and the transmittance for light used for selective exposure of the upper resist layer is increased by heating or whole surface exposure treatment. The greatest feature is that the transmittance is reduced and the transmittance for the mask alignment light is increased.

In the present invention, when an aromatic sulfonyl azide compound is mixed with a polymer compound (polymer) and used as a material for an organic layer as a lower layer, the aromatic sulfonyl azide compound used has a maximum absorption wavelength of light when exposing a photoresist layer as an upper layer. Is selected to suit the wavelength used for. For example, in order to absorb light of 436 nm which is the exposure wavelength of a general-purpose reduction projection exposure method, it is desirable to select an aromatic sulfonyl azide compound having an absorption maximum wavelength of 350 to 450 nm.
Then, as the aromatic sulfonyl azide compound, for example, the compounds shown in Table 1 can be used.

Further, in the multilayer resist process according to the present invention,
An intermediate layer such as an SOG layer or a photoresist as an upper layer is directly applied on the lower organic layer. Therefore,
The organic material layer as the lower layer needs to be insoluble in the organic solvent for the polymer constituting the lower layer by baking or whole surface exposure treatment. To this end, it is desirable that the aromatic sulfonyl azide compound be bifunctional, that is, a bissulfonyl azide compound. However, in the present specification, as will be described later, it is also possible to allow the sulfonyl azide compound to share the light absorption property and the solvent insolubilization property to another kind of compound, for example, light or heat such as an aromatic azide compound. Therefore, a compound that can insolubilize the polymer can be added. Examples of such azide compounds include 3,3 ′
-Diazido dophenyl sulfone, 4,4'-diazido diphenyl methane, 4,4'-diazido diphenyl ether, 4,4 '
A bisazide compound such as -diazidodiphenyl sulfide, 4,4'-diazidodiphenyl disulfide, 4,4'-diazidodiphenyl sulfone, 4,4'-diazidostilbene is used. It is also possible to use a thermosetting resin as the polymer forming the lower layer.

As a material for the lower organic material layer in the multilayer resist process of the present invention, a thermosetting resin or a polymer which can be thermally or photochemically cured or insolubilized in a solvent by an aromatic azide compound is used. For example, novolac resin, phenol resin such as polyvinyl phenol, natural rubber, modified rubber such as cyclized natural rubber, polybutadiene,
Synthetic rubbers such as polyisoprene, cyclized polybutadiene, cyclized polyisoprene, and styrene-butadiene rubber, and synthetic polymer compounds such as polystyrene, iodine polystyrene, polyvinyl butyral, polyethyl methacrylate, polyglycidyl methacrylate, and polymethylisopropenyl ketone Can be used.

In the lower organic material layer in the present invention, the baking treatment temperature for reacting the aromatic sulfonyl azide compound or the aromatic azide compound and the polymer constituting the lower layer to carry out the insolubilization reaction is preferably 100 to 300 ° C., and further 140
A temperature range of up to 250 ° C is more preferred. Further, the light used for the entire surface exposure treatment may be any light in the wavelength range of 200 to 300 nm, and the above insolubilization reaction can be sufficiently advanced.

The aromatic sulfonyl azide compound used in the lower organic compound layer of the present invention can be easily obtained by changing the acid chloride of an aromatic sulfonic acid or its salt and treating it with sodium azide or the like. Usually, an acid dye or a direct dye, which is a water-soluble dye, is often an aromatic sulfonic acid derivative, and dyes having many color tones are prepared. Therefore, depending on the exposure light wavelength of the upper photoresist layer and the wavelength of the alignment mark detection light in the multi-layer resist process, a suitable light absorber for the lower organic layer is selected from these various dyes and the sulfonyl azide is selected. It is also possible to apply the present invention to a system compound.

Example of Invention

Example 1 First, an example of the multilayer resist process according to the present invention will be described in more detail with reference to the drawings. As shown in FIG. 1 (a), an Al film 2 as a film to be processed was formed on a Si substrate 1 having a step on the surface. In order to flatten the step,
The organic layer 3 as the lower layer uses polyvinylphenol as a polymer and as an aromatic sulfonyl azide compound,
20 wt% of 1-phenyl-3-methyl-4- (p-azidosulfophenylazo) -5-pyrazolone was added to the polymer, and 3,3'-diazidodiphenyl was added as a thermal crosslinking agent. 20% by weight of sulfone was added to the polymer, dissolved in cyclohexanone, and spin-coated to form the sulfone. After that, baking treatment was performed at a temperature of 200 ° C. for 20 minutes. At this stage, the exposure wavelength of the lower organic layer 3
The transmittance for 436 nm light was 0% in terms of film thickness of 1 μm, and it was possible to completely prevent the influence of reflected light from the substrate during exposure. Next, a silicon compound was applied as the intermediate layer 4 by a known method, and a positive photoresist was applied on the silicon compound to form a photoresist layer 5. Thereafter, as shown in FIG. 1 (b), a desired resist pattern 5'was formed by a normal photolithography method. At this time, the shape of the resist pattern 5'is good,
It was confirmed that the exposure light was efficiently absorbed by the lower organic layer 3. After that, as shown in FIG. 1 (c),
The intermediate layer 4 is selectively etched using the resist pattern 5'as a mask to form a mask pattern 4'consisting of the intermediate layer 4, and the exposed portion of the lower organic compound layer 3 is subjected to a reactive plasma etching method or a sputtering etching. Etching was sequentially performed by the method to form a desired pattern. As a result, as shown in FIG. 1 (c), it was possible to form a pattern having a high dimensional accuracy and a good shape.

The lower organic material layer 3 of this embodiment has an alignment mark detection light, for example, light of 546 nm, which is 8
It shows a transmittance of 2%, which is 64% after baking at 200 ° C.
% Has changed. On the other hand, 1-phenyl-3-methyl-4- (p-azidophenylazo) -5-pyrazolone, which has the same skeleton as the above-mentioned azide compound, is 90% before baking.
%, The light transmittance decreased to 26% by the 200 ° C baking treatment. As described above, it was confirmed that the aromatic azide compound significantly changes the transmittance of the alignment detection light.

(Example 2) As the light absorber for the lower organic layer 3, 4-N, N-dimethylamino-4'-azidosulfoazobenzene was used instead of the light absorber used in Example 1. As a result, the transmittance of light having a wavelength of 436 nm before and after baking is
The transmittances of light having a wavelength of 546 nm were 55% and 54%, respectively. As described above, it was confirmed that the baking hardly changed the transmittance. On the other hand, 4-N, N-dimethylamino-4'-azidoazobenzene, which has the same skeleton and whose azido group is directly bonded to the benzene nucleus, can be baked under the same conditions (200 ° C, 20 minutes). Therefore, the transmittance of light with a wavelength of 436 nm hardly changes to 0% before baking and 1% after baking, but the transmittance for light of 546 nm is 89% before baking and 37% after baking. And drastically decreased.

As described above, the aromatic sulfonyl azide compound was found to have a smaller spectral change due to the baking treatment than the aromatic azide compound, and moreover, the transmittance of the exposure light and the mark detection light of the upper photoresist layer in the multilayer resist process. It was found that the ratio of is large and the alignment accuracy can be improved.

Example 3 Instead of the light absorbent of the lower organic layer 3 used in Example 1, acid dye Kayanol Yellow N5G (manufactured by Nippon Kayaku Co., Ltd.) was converted to sulfonic acid chloride with thionyl chloride in dimethylformamide, followed by azide. A light absorber that was sulfonylazidated by treatment with sodium iodide was used. The infrared spectrum of this absorber is
The absorption of the sulfonyl azide group is shown at 2130 cm ^-1 . As a result, before and after baking at 200 ° C. for 15 minutes, the transmittance for 436 nm light was 2% and the transmittance for 546 nm light was 98% and 91%, respectively. Was given. FIG. 2 shows the change in the spectrum of the light absorbent before and after the baking treatment in this example. In the figure,
(Α) is a curve showing the change in spectrum before the baking treatment, and (β) is a curve showing the change in the spectrum after the baking treatment. As described above, by using the lower organic material layer having good light absorption of exposure light and high transparency for pattern matching detection light in a multilayer resist process, a fine pattern with extremely high dimensional accuracy is obtained. I was able to.

〔The invention's effect〕

As described in detail above, in the multi-layer resist process according to the present invention, when an aromatic sulfonyl azide compound is contained in the lower organic compound layer to be coated on the substrate, the lower organic compound layer is formed by baking treatment or whole surface exposure treatment. Does not volatilize from within the layer by reacting with the polymer within,
It has good absorptivity for exposure light, high transparency for detection light for pattern matching, and an organic layer that is insoluble in the solvent can be obtained. As a result, an excellent resist pattern with high dimensional accuracy and good shape can be obtained. Therefore, according to the present invention, an extremely fine pattern can be formed with high dimensional accuracy and positional accuracy even if there are irregularities or steps on the surface of the substrate, and a semiconductor integrated circuit device or a magnetic bubble with high integration density can be formed. It is extremely effective in manufacturing various devices such as memory devices.

[Brief description of drawings]

1 (a), (b) and (c) are process drawings for explaining the process of the multilayer resist method according to the present invention, and FIG. 2 is a graph showing an absorption spectrum of a light absorbent in Example 3 of the present invention. Is. 1 ... Si substrate, 2 ... Al film, 3 ... organic material layer (lower layer),
3 '... lower layer pattern, 4 ... intermediate layer, 4' ... intermediate layer pattern, 5 ... resist layer (upper layer), 5 '... resist pattern.

Front page continuation (72) Inventor Seiichiro Shirai 1450, Kamimizuhoncho, Kodaira-shi, Tokyo Inside the Device Development Center, Hitachi, Ltd. Computer Business Division (72) Inventor, Kazuya Kadota 1450, Kamimizumoto-cho, Kodaira-shi, Tokyo Hitachi, Ltd. Musashi Plant (56) References JP-A-57-168247 (JP, A) JP-A-54-87525 (JP, A) JP-A-59-114824 (JP, A) JP-B-4-77899 ( JP, B2)

Claims (9)

[Claims] 1. An organic material layer containing at least an aromatic sulfonyl azide compound and a polymer compound or an aromatic sulfonyl azide compound, an aromatic azide compound and a polymer compound is formed on a substrate having a step on the surface. A step of flattening the surface, a step of heating or exposing the entire surface of the organic material layer, a mask pattern made of a material having a desired shape on the organic material layer and having a larger dry etching resistance than the organic material layer. And a step of removing the exposed portion of the organic material layer by dry etching, the pattern forming method. 2. The pattern forming method according to claim 1, wherein the mask pattern comprises a resist layer formed on the organic material layer. 3. The pattern forming method according to claim 1, wherein the mask pattern comprises an intermediate layer formed on the organic material layer. 4. The aromatic sulfonyl azide compound is at least 1 selected from the group of compounds shown in Table 1 below.
The pattern forming method according to any one of claims 1 to 3, wherein the pattern forming method is a seed. 5. The aromatic sulfonyl azide compound is a sulfonyl azide compound obtained by treating an acidic dye which is an aromatic sulfonic acid derivative or a direct dye with an azide. The pattern forming method according to any one of claims 1 to 3. 6. The aromatic azide compound is 3,3'-diazidodiphenylsulfone, 4,4'-diazidodiphenylmethane, 4,4'-diazidodiphenyl ether, 4,4'- Diazidodiphenyl sulfide, 4,4'-diazidodiphenyl disulfide, 4,4'-diazidodiphenyl sulfone, 4,
The pattern forming method according to any one of claims 1 to 3, which is at least one selected from the group of 4'-diazidostilbenes. 7. The polymer compound is a novolac resin, polyvinylphenol, natural rubber, cyclized natural rubber, polybutadiene, polyisoprene, cyclized polybutadiene, cyclized polyisoprene, styrene-butadiene rubber, polystyrene, iodinated polystyrene, Polyvinyl butyral,
4. The pattern forming method according to claim 1, wherein the pattern forming method is at least one selected from the group consisting of polymethylmethacrylate, polyglycidylmethacrylate, and polymethylisopropenylketone. . 8. The pattern forming method according to claim 1, wherein the heat treatment is performed at a temperature of 100 to 300 ° C. 9. The pattern forming method according to claim 1, wherein the entire surface exposure processing is performed using light having a wavelength of 200 to 300 nm.