JPH0149013B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pattern forming method for manufacturing semiconductor integrated circuits, optical integrated circuits, Josephson devices, and the like.

[Background of the invention]

The lift-off method is used as a method for obtaining a desired pattern without etching the material to be processed during the processing of LSI and other devices. In this method, high-energy rays such as electron beams, light, ultraviolet rays, and X-rays are
A sensitive material sensitive to this is irradiated and developed to form the cross-sectional shape of the undercut. Using this pattern as a mask, a material to be processed is deposited by vapor deposition or other methods, and then the material forming the pattern is removed to obtain a desired pattern. In this method, it is important to form the cross-sectional shape of the undercut in order to remove the material forming the pattern.

Conventionally, the following method has been used to obtain the above-mentioned cross-sectional shape.

(1) Using a single layer of positive resist, electron beam,
When irradiation with light, X-rays, etc. or development is performed excessively, the cross-sectional shape of the resist pattern 1 has a so-called undercut shape in which the interface dimension _d2 is wider than the opening dimension d1, as shown in FIG _. 1a. It takes advantage of becoming. Although this method is simple, it is possible to control the dimensions and cross-sectional shape, i.e., the opening size.
There was a problem in that it was difficult to control d ₁ and interface dimension d ₂ , and in particular, it was difficult to obtain a fine opening dimension d ₁ .

(2) By using positive resists with different dissolution rates in the same developer, and using a two-layer structure in which the resist with a faster dissolution rate is used as the lower layer and the resist with a slower dissolution rate is used as the upper layer, the cross-sectional shape is as shown in Figure 1b. There is a way to get a pattern. 2 is the lower resist pattern,
3 is an upper layer resist pattern. In this method, if the dissolution rate ratio between the upper layer and the lower layer is small, the upper resist layer will continue to dissolve while the lower resist layer is dissolving, making it difficult to obtain fine opening dimensions and difficult to control the cross-sectional shape as in (1). There was a problem.

Method (2) generally utilizes the phenomenon that the dissolution rate depends on the molecular weight, and there is a method in which resists having different molecular weights are stacked. In this case, there is a problem that there is a limit to the molecular weight ratio that can be achieved and that the lower resist layer is easily dissolved during coating of the upper resist layer, making it difficult to create a two-layer structure with a high dissolution rate ratio.

[Purpose of the invention]

An object of the present invention is to provide a pattern forming method that can eliminate these problems and obtain a pattern with a desired cross-sectional shape.

[Summary of the invention]

In order to achieve the above object, the present invention is to laminate resist compositions whose dissolution rate can be controlled by adjusting the concentration of additives and the heat treatment temperature. That is, in the present invention, at least two layers of pattern-forming materials having different dissolution rates in the same developer are laminated on a substrate to be processed, and the pattern-forming materials are developed by irradiating them with high-energy rays such as electron beams, light, ultraviolet rays, and X-rays. In the method of forming a pattern, a resist having a carboxyl group in a side chain is used as a pattern forming material, and an additive selected from at least one of divalent metal oxides, metal halides, and organic acid salts. A positive resist composition consisting of a homogeneous mixture is used, and the positive resist compositions having different concentrations of additives are heat-treated and laminated, or the positive resist compositions having the same concentration of additives are laminated at different temperatures. The method is characterized in that a pattern is formed by irradiating the pattern-forming material obtained by heat-treating and laminating the material with the high-energy rays and then developing it.

[Embodiments of the invention]

The invention will now be explained in detail with reference to the drawings.

Figure 2 shows the dissolution rate depending on the additive concentration (% by weight relative to the resist) and heat treatment temperature when phenyl methacrylate methacrylic acid copolymer (φ-MAC) is used in a positive resist and zinc bromide is used as an additive. . The horizontal axis is the electron beam irradiation amount, and the vertical axis is φ
- Dissolution rate of MAC. The composition of the developer is 1,
4-dioxane: diisobutyl ketone = 30:70
(volume ratio). Further, the slope of the straight line in the figure, that is, the rate of change in the dissolution rate with respect to the irradiation dose, is an index of the resolution of the resist, and the larger the rate of change, the higher the resolution. In the figure, A shows the added concentration of zinc bromide at 0% by weight and a heat treatment temperature of 200°C, B shows an added concentration of zinc bromide of 1% by weight and a heat treatment temperature of 180°C, and C shows the added concentration of zinc bromide at 180°C. 1% by weight, heat treatment temperature 200℃,
In D, the concentration of zinc bromide added is 3% by weight, and the heat treatment temperature is 160°C; in E, the concentration of zinc bromide added is 3% by weight,
The heat treatment temperature was 180°C, the concentration of zinc bromide added was 3% by weight, and the heat treatment temperature was 200°C. According to the results, the larger the amount of zinc bromide added and the higher the heat treatment temperature, the higher the molecular crosslink density and the lower the dissolution rate, but the rate of change in the dissolution rate became larger.

A specific example is shown in FIG.

After spin-coating the additive-free φ-MAC on the substrate, it is heat-treated or prebaked at 200°C (see A in Figure 2). The coating film thickness is 4000 Å. The coating solvent is a mixture of 50% monochlorobenzene and 50% dioxane (by volume). Next, φ-MAC with 3% by weight of zinc bromide added on this sample.
Spin coat and pre-bake at 180°C (Figure 2 E). The coating thickness of the upper layer is 3000Å,
The coating solvent is methyl isobutyl ketone. This sample is irradiated with an electron beam at an accelerating voltage of 30 kV in a line shape with a width of 0.3 μm. The irradiation dose was 260 μC/cm ² .

Next, this sample was immersed in a mixture of 30% dioxane and 70% diisobutyl ketone and developed.
A pattern having an opening size of 0.4 μm, an interface size of 1 μm, and an undercut-like cross-sectional shape consisting of the lower resist pattern 4 and the upper resist pattern 5 could be formed. When lift-off of Al was performed using this pattern, a line pattern of Al with a width of 0.4 μm was obtained.

Next, another embodiment of the present invention is shown in FIG. In the embodiments described above, a resist with a fast dissolving rate was used as the lower layer, but conversely, a resist with a slow dissolving rate was used as a lower layer and a resist with a fast dissolving rate was used as an upper layer.

φ- to which 1% by weight of zinc bromide was added on the substrate.
Spin coat the MAC and pre-bake at 200°C (Figure 2, c). The coating film thickness is 3000 Å. The coating solvent is a mixture of 50% monochlorobenzene and 50% dioxane. Furthermore, additive-free φ-MAC was spin-coated on this sample,
Pre-bake at 200℃ (Figure 2 A). The coating film thickness is 3000 Å. The coating solvent is methyl isobutyl ketone. Next, apply an accelerating voltage of 30 kV to this sample.
The electron beam is irradiated in a line shape with a width of 0.3 μm. The irradiation dose was 200 μC/cm ² . Next, when this sample was immersed in a mixed solution of 30% dioxane and 70% diisobutyl ketone and developed, the opening size was 1 μm and the interface size was 0.4 μm.
An overcut cross-sectional shape of m was obtained.

In the above embodiments, phenyl methacrylate methacrylic acid copolymer (φ-MAC) was used as the positive resist material, but other materials may be used as long as they have carboxyl groups in their side chains. Although zinc bromide is used as an additive, other additives selected from at least one of divalent metal oxides, metal halides, and organic acid salts may also be used. Furthermore, in the above example, positive resist compositions with different concentrations of additives were heat-treated and laminated, but positive resist compositions with the same concentration of additives may be heat-treated at different temperatures and laminated. This is also clear from Figure 2.

As mentioned above, a two-layer structure in which a resist with a fast dissolution rate is the lower layer and a resist with a slow dissolution rate is the upper layer can be applied to a fine lift-off pattern because a pattern with an undercut cross-sectional shape can be obtained. On the other hand, in a configuration in which a resist with a slow dissolution rate is the lower layer and a resist with a faster dissolution rate is the upper layer, a pattern with an overcut cross-sectional shape is obtained. Using this pattern as a mask, use the dry etching method to
If the contact hole is processed under conditions where the etching speed of the resist material and the material to be processed are almost equal,
A tapered contact hole having a shape similar to that of the pattern shown in FIG. 4 can be formed, and disconnection of the wiring material can be made less likely to occur.

〔Effect of the invention〕

As explained above, the present invention provides a homogeneous mixture (additive Since a positive resist composition consisting of a mixture (mixture in which the ionomer is uniformly distributed) forms an ionomer through heat treatment and thermal crosslinking occurs, the crosslinking density can be controlled by the amount added and the heat treatment temperature. Therefore, the cross-sectional shape of the resist pattern can be controlled by laminating the positive resist compositions having different additive concentrations. Furthermore, since the dissolution rate can be easily controlled by adding additives and the amount of control is large, a multilayer resist structure with a large dissolution rate ratio between the upper layer and the lower layer can be formed, and the cross-sectional shape can be controlled over a wide range. This has the effect of obtaining a pattern with fine dimensions.
Furthermore, since the solvent becomes insoluble by adding additives and performing heat treatment, it is possible to overcoat the same resist with different additive concentrations.

[Brief explanation of drawings]

Figures 1a and b show the conventional pattern forming method, respectively, and Figure 2 shows the φ-MAC dissolution rate depending on the concentration of zinc bromide (wt% relative to the resist) and heat treatment temperature (°C). Figure shown, 3rd
FIG. 4 is a diagram showing an embodiment of the present invention, respectively. d ₁ --- Opening dimension, d ₂ --- Interface dimension, 1 --- Resist pattern, 2, 4 --- Lower layer resist pattern, 3, 5 --- Upper layer resist pattern.

Claims (1)

[Claims] 1 In a method of forming a pattern by laminating at least two layers of pattern forming materials having different dissolution rates in the same developing solution on a substrate to be processed and developing them by irradiating them with high energy rays, a side chain is used as the pattern forming material. A positive resist composition comprising a homogeneous mixture of a resist having a carboxyl group and an additive selected from at least one of a divalent metal oxide, a metal halide, or an organic acid salt is used, and the additive is The pattern forming material obtained by heat treating and laminating the positive resist compositions having different concentrations of additives, or by heat treating and laminating the positive resist compositions having the same additive concentration at different temperatures. , irradiate with the above high energy rays,
A pattern forming method characterized by forming a pattern by subsequent development.