JPS6199331A - Fine pattern formation - Google Patents

Abstract

PURPOSE:To prevent reduction of resolution and change of resist method by using a resin which contains a coloring matter which almost perfectly absorbs definite wave length light and has no deterioration of light absorbing characteristics during the heat treatment in a process as a low layer resist. CONSTITUTION:The first process wherein the thin layer of a resin composition of preventing reflection adheres, the second process wherein a silica thin layer is laminated on the resin layer, the third process wherein a photo resist film is coated on the silica thin layer and the fourth process wherein an upper resist pattern is formed removing a required part by selective exposure and a development process from the photo resist film are contained on the surface of a semiconductor substrate. The fifth process wherein the required pat of the silica thin layer is removed by etching with gas plasma including freon gas using the resist pattern as a mask and the sixth process wherein the required part of the resin layer is removed by etching with gas plasma including oxygen are also contained. The resin composition of preventing reflection contains an absorbing agent shown by Formula in novolak resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fine pattern forming method for realizing semiconductor devices such as IC, L, 9I, etc.

[Conventional technology]

In recent years, semiconductor devices such as LSI and VLSI have appeared that contain tens to millions of semiconductor elements in one chip, and as a result, the packaging density of the elements in the devices has become extremely large, and the semiconductor substrate There will be a demand for miniaturization of the element patterns formed thereon.

One possible method for miniaturizing device patterns is to make the applied resist film thinner than before, but in this method, the resist film thickness at the step portions is reduced due to the coverage of the resist film against the steps on the substrate surface. Because it tends to be insufficient,
Pinho! This causes problems such as the occurrence of pores and the inability to ensure a sufficient resist film thickness during etching processing after resist pattern formation, and a resist film thickness of about 1 μm or more is practically required.

Due to these factors, a three-layer resist method has recently been proposed for forming fine patterns for realizing large-scale integrated circuits.

In this three-layer resist method, a resist film is usually formed as an organic material film on a substrate, and has a three-layer structure consisting of an inorganic material layer as an intermediate layer that serves as a mask for etching the organic material film, and an upper layer of a photoresist film layer. Because of this, it is called the three-layer resist method.

This three-layer resist method forms fine patterns for the following purposes. That is, as shown in Figure 2-1, first, about 0.5 μm
For example, Sumiresyst D F2200 positive photoresist manufactured by Sumitomo Chemical Co., Ltd. or Shipley is applied onto the semiconductor substrate 1 having the surface step 2.
After applying a phenol novolac positive resist such as AZ 1350 J manufactured by Co., Ltd. to a thickness of about 1.8 μm using a spin code method, it was coated on a hot plate at about 150 °C for 8
The lower resist layer 11 is formed by heat treatment for a second.

Next, a spin-on glass (SOO) material such as Accuglass NP-5R manufactured by Sumitomo Chemical Co., Ltd. is applied on the lower resist layer 11 by the same spin code method.
The intermediate layer 12 made of silica material and having a thickness of 0.12 μm is formed by heat treatment on a hot plate at 00'C for 60 seconds (FIG. 2-2).

Next, on the intermediate layer 12, a positive resist A made by Silapray was applied.
Z1470J is applied to a thickness of 0.6 μm by the spin code method in the same manner as the above two layers, and a hot plate heat treatment is performed at 100° C. for 45 seconds to form the upper resist layer 13 (FIG. 2-8).

Next, 1.
I: Predetermined portion 3 of layer resist layer 18 is removed to form upper resist pattern 18A (FIGS. 2-4).

Next, using the upper resist pattern 18A as a mask, etching is performed using a mixed gas plasma of fluorocarbon gas (OF4) and hydrogen (H2) in a parallel plate type reactive ion etching apparatus.
A predetermined portion of the silica intermediate layer 12 is removed to form a silica intermediate layer pattern 12A (FIG. 2-5).

Subsequently, when the etching gas of the reactive ion etching apparatus is changed to 02 and etching processing is further performed for a predetermined time, a predetermined portion 3 of the lower resist layer 11 is removed and a lower resist pattern 11A is formed. The 8-layer resist is completed using the layer resist method (2nd-
Figure 6) The three-layer resist method using the above method allows the upper resist layer 13 to be dramatically thinner than the single-layer resist, and the lower organic film layer 11 flattens the level difference on the substrate surface. As a result, pattern resolution and dimensional controllability are significantly improved.

[Problem that the invention seeks to solve]

However, the current 3F4 resist method has the following problems and does not necessarily provide resolution and dimensional stability close to the theoretical values.

That is, when the upper resist layer is exposed to light, double opposition from the substrate surface occurs, which may cause a decrease in resolution and a variation in dimensions.

This is especially noticeable when using aluminum or polycrystalline silicon, which has a high surface reflectance, and the surface level difference is large, resulting in resist resolution that is much lower than the aerial resolution provided by the exposure equipment. Variation in resist pattern dimensions from region to region also poses a serious problem.

The purpose of the present invention was to overcome the above-mentioned problems in the multilayer resist method, and to develop a new Wi thin pattern forming method that prevents resolution degradation and resist dimension fluctuations caused by ultraviolet light reflection on the substrate surface. This is what we provide.

[Means for solving problems]

The outline of the present invention is to attach a resin as a lower resist layer to the lower resist layer, which contains a coloring material that almost completely absorbs light of a predetermined wavelength and whose light absorption characteristics do not deteriorate due to heat treatment during the process. It's there. That is, the present invention comprises: (1) a first step of depositing a thin layer of an antireflection resin composition on the surface of a semiconductor substrate; a second step of laminating a thin layer of silica on the resin layer; a third step of applying a photoresist film thereon; a fourth step of removing a predetermined portion of the photoresist film by selective exposure and development treatment to form an upper resist pattern; and masking the resist pattern. a fifth step of removing a predetermined portion of the silica thin layer by etching with a gas plasma containing chlorofluorocarbon gas;
and a sixth step of removing a predetermined portion of the resin layer by etching with oxygen-containing gas plasma, and the antireflection resin composition contains a light absorbing agent represented by the following general formula in the novolak resin. and (2) a fine pattern forming method characterized in that the antireflection resin composition contains a novolak resin and a light absorber and a photosensitizer represented by the above general formula. .

Examples of the novolak resin used in the present invention include phenol-formaldehyde novolak resin, cresol-formaldehyde novolak resin, and tert-butylphenol-formaldehyde resin.

Specific examples of the light absorbing agent represented by the above general formula used in the present invention include the following compounds.

4-(N,N-di-n-hexyl)-anilinomethylidenemalononitrile, 4-(N,N-di-n-pentyl)-3-methylanilino-methylidenemalononitrile, 4-(N,N -G-n
-pentyl)-2-methylanilino-methylidenemalononitrile, 4-(N,N-di-n-hexyl)-2-methylanilino-methylidenemalononitrile, 4-(N,
4-(N,N-di-heptyl)-anilino-methylidenemalononitrile, 4-(N,N-di-n-heptyl)-2 -Methylanilino-methylidenemalononitrile, 4-(N,N-di-n
-hexyl)-anilino-methylidene-dimethylmalomamate, 4-(N,N-di-n-hexyl)-2-meth1
Thylanilino-dimethylmalomamate.

4-(N,N-di-n-pentyl)-3-methylanilino-methylidene-dimethylmalomate, 4-(N,N-di-n-hexyl)-2-methoxyanilino-methylidenemalononitrile, 4 -(N, N-ji-
n-hexyl)-2-chloroanilino-methylidenemalononitrile, 4-(N,N-di-n-hexyl)-3-
Methoxyanilino-methylidene malononitrile, 4-(
N,N-di-n-hexyl)-3-methoxyanilino-
Methylidenemalononitrile, 4-(N,N-di-n-pentyl)-2-chloroanilino-methylidene-dimethylmalomate, 4-(N,N-di-benzyl)-anilino-methylidenemalononitrile.

More preferably used light absorbing agents include the compounds shown in Table 1.

@Table 1 The amount of light absorbing agent to be used is 2 to 60 times the novolac resin, as an excessive amount will cause a decrease in sensitivity, and a small amount will decrease the antireflection ability! The content is preferably from 8 to 40% by weight.

Since these light absorbers have extremely good solubility in novolac resins, they are completely dissolved for a long period of time even in the coating film after baking, forming a stable coating film. In particular, in the general formula of the light absorbing agent described above, the number of carbon atoms in R5 and R6 is 4.
The above light absorbing agent has extremely good solubility in novolak resin, and the number of carbon atoms in Ra and R6 is preferably 4 to 7. In addition, these light absorbers have strong absorption of ultraviolet light, especially the G-line (486 nm) portion of ultraviolet light, and most of the light in the visible range necessary for alignment etc. is transmitted, making it possible to accurately align the mask. It also exhibits a sufficient antireflection effect.

The antireflection resin composition of the present invention is dissolved in a solvent such as ethylene glycol monoethyl ether acetate or cyclohexanone and used in the same manner as in applying a conventional photoresist.

Further, a photosensitizer such as naphthoquinone diazide sulfonic acid ester or benzoquinone diazide sulfonic acid ester used in ordinary positive resists may be added to this antireflection resin composition. The amount of the photosensitizer added is preferably 5 to 50% by weight based on the novolac resin. When the antireflection resin composition contains a photosensitizer, the adhesion between the antireflection resin composition and the substrate during development is improved, and resolution can be further improved.

When the antireflection resin composition of the present invention is used, there is no decrease in sensitivity on a substrate with high reflectance, and a decrease in resolution due to reflection can be prevented. Further, the light absorbing agent contained in the antireflection resin composition of the present invention has excellent stability during prebaking at 80° C. to 100° C., making it possible to form a pattern with good reproducibility. Furthermore, this light absorbing agent has excellent solubility in novolac resin, and can maintain its performance even if left for a long time after prebaking.

〔Effect of the invention〕

In this way, the light absorbing agent contained in the lower resist layer can almost completely prevent reflected light from the substrate surface, significantly reducing the deterioration of resist pattern resolution and dimensional stability due to one reflected light, and improving the aerial resolution of exposure equipment. It is now possible to faithfully reproduce resist patterns. In other words, it has become possible to create a resist pattern on a semiconductor substrate with much better width and dimensional stability than the current 8-round resist method.

This makes it possible to reduce the chip size of the device by miniaturizing the element pattern on the LSI, making a considerable contribution to improving the electrical characteristics of the LSI and reducing the manufacturing cost of the device.

Hereinafter, the fine puff forming process of the present invention will be explained in detail in Examples with reference to the drawings.

〔Example〕

Example 1 A light absorber having a main absorption wavelength at 14861 m (absorbent listed in Table 1) was added to a novolac resin Alnovol PN480 (manufactured by Hoechst) containing 10y of ethylene glycol mono(ethyl ether acetate soluble ac novolac resin content: 10% by weight). I light agent 41)6. An antireflection resin composition was prepared by adding Qi. This anti-reflection resin composition was mixed with about 0.
It was coated on a semiconductor substrate 1 having a surface step 2 of 5 μm to a thickness of about 1.8 μm using a spin code method, and heated at 120°C and 9 μm.
A hot plate heat treatment is applied for 0 seconds to form the lower resist layer 14 (Fig. @l1).

The subsequent steps are almost the same as the well-known three-layer resist method.
The first step is to form the silica intermediate layer 12 on the resist layer 14.
2), and further form an upper resist layer 18 (1st-
Figure 8).

Subsequently, a predetermined portion 4 of the upper resist layer 18 is removed by selective exposure and development using a reduction exposure device to form an upper resist pattern 18B (FIGS. 1-4).

Next, a predetermined portion 4 of the silica intermediate layer 12 is removed by etching using a mixed gas plasma of fluorocarbon gas (OF4) and hydrogen (2) using the upper resist pattern 18B as a mask to form a silica intermediate layer pattern 12B (first
-5 figure).

Finally, a predetermined portion 4 of the lower resist layer 14 and the upper resist pattern 18B are removed by etching with oxygen (02) plasma gas to form a lower resist pattern 14A, completing the resist pattern by the three-layer resist method according to the present invention. Figures 1-6).

Example 2 Novolac resin Alnovol PN480 (manufactured by Hoechst) 15 liters and 2.8.4-trihydroxybenzophenone-naphthoquinocyne 1.2-diazido-5-sulfonic acid-(mono, di, tri) ester mixture 1.52 liters 4,860 m
A light absorbent having a main absorption wavelength at
) 9.0 y was added to prepare an antireflective composition. When this was used to form a bubble similar to that in Example 1, the resolution and dimensional stability of the bubble were significantly improved compared to the current three-layer resist method.

[Brief explanation of the drawing]

1-1 to 1-6 are cross-sectional views showing the fine pattern forming method of the present invention, and FIGS. 2-1 to 2-6 show the steps of the prior art in order of process. FIG. Note that the numbers in the figure indicate the following. 1...Silicon substrate, 2...Difference, 11.14...
・Lower resist layer, 12...Silica intermediate layer, 13...
- Upper resist layer, IIA, 14A... Lower rN resist pattern, 12A, 12B... Intermediate layer pattern, 1
8A, 18B...upper resist pattern, 3, 4
...Predetermined exposure area

Claims (2)

[Claims] (1) A first step of depositing a thin layer of an antireflection resin composition on the surface of a semiconductor substrate, a second step of laminating a thin silica layer on the resin layer, and a photoresist film on the thin silica layer. a third step of coating the photoresist film, a fourth step of removing a predetermined portion of the photoresist film by selective exposure and development treatment to form an upper resist pattern, and etching with gas plasma using the resist pattern as a mask. a fifth step of removing a predetermined portion of the silica thin layer by etching with oxygen-containing gas plasma, and a sixth step of removing a predetermined portion of the resin layer by etching with oxygen-containing gas plasma, wherein the antireflection resin composition is a novolak. The resin has the following general formula▲mathematical formula, chemical formula, table, etc.▼ [R_1, R_2: cyano group or COOR_
7 groups (R_7; lower alkyl group) R_3, R_4: groups each selected from a hydrogen atom, lower alkyl, lower alkoxy, lower acylamino, or halogen R_5, R_: groups each selected from alkyl and aralkyl] A fine pattern forming method characterized by containing an agent. (2) A first step of depositing a thin layer of an antireflection resin composition on the surface of the semiconductor substrate, a second step of laminating a thin silica layer on the resin layer, and a photoresist layer on the thin silica layer. A third step of applying a film, a fourth step of removing a predetermined portion of the photoresist film by selective exposure and development treatment to form an upper resist pattern, and etching with gas plasma using the resist pattern as a mask. a fifth step of removing a predetermined portion of the silica thin layer by etching with oxygen-containing gas plasma, and a sixth step of removing a predetermined portion of the resin layer by etching with oxygen-containing gas plasma, wherein the antireflection resin composition is a novolak. The resin has the following general formula ▲ Numerical formula, chemical formula, table, etc. ▼ [R_1, R_2: each cyano group or COOR_7
Group (R_7: lower alkyl group) R_3, R_4: groups each selected from a hydrogen atom, lower alkyl, lower alkoxy, lower acylamino, or halogen R_5, R_6: groups each selected from alkyl and aralkyl] A light absorbing agent represented by the following. and a photosensitizer.