JPH04306828A - Patterning process - Google Patents

Abstract

PURPOSE:To simplify the title process by a method wherein an inorganic matter such as silicon oxide etc., is used as an etching mask so as to form an oxygen plasma blocking layer by the oblique sputtering process after the formation of upper layer resist patterns. CONSTITUTION:The plasma blocking film 13 comprising e.g. a silicon oxide film of 1500Angstrom thick are formed on the surfaces of upper layer resist patterns 12A. At this time, the sputtering angle is selected so that the exposed lower resist layer 11 may not be covered with silicon oxide. Later, the lower resist film 11 is anisotropically etched away using oxygen plasma by ECR plasma etching step to form lower layer resist patterns 11A for the completion of the specific multilayer resist patterns. Within these multiple resist patterns thus completed, the fine patterns formed on the upper resist film are transferred to the lower layer resist film 11 with high precision.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a patterning method, and more particularly to a method for patterning multilayer resists in the manufacture of semiconductor devices and the like.

[0002] In recent years, patterns of semiconductor ICs have been becoming finer in response to demands for higher integration and higher density, and it is certain that this trend will continue in the future. In order to form a wiring pattern or the like on a substrate, it is first necessary to form a resist pattern. Single-layer resist methods have been widely used to form resist patterns, but as patterns become finer, various problems have become apparent. For example, when there is a large step on the substrate surface, the resist film becomes considerably thick in the recessed portion, making it difficult to obtain uniform resolution. Furthermore, if the substrate surface is made of a metal that reflects a lot of light, pattern accuracy will be impaired due to interference between incident light and reflected light.

A multilayer resist method has been proposed as a means of solving these problems and forming fine resist patterns with high precision, and currently the three-layer resist method and the two-layer resist method are being developed. In both of these methods, a high-resolution resist pattern is formed by exposing and developing a flat, thin upper resist film, and this pattern is transferred with high precision to the layer below by anisotropic dry etching.

0004

2. Description of the Related Art A conventional method for patterning a multilayer resist will be described with reference to FIGS. 2 and 3. In both figures, the same parts as in FIG. 1 are given the same reference numerals.

FIGS. 2(a) to 2(d) are schematic sectional views showing a first example of a conventional method in the order of steps. This method is an example of a three-layer resist method. First, a lower resist film 11, an intermediate layer 21, and an upper resist film 12 are sequentially formed on a substrate 1 (see FIG. 2(a)). The lower resist film 11 is the substrate 1
It flattens the surface level difference and prevents light reflection from the surface of the substrate 1 during exposure, and the film thickness is thick (for example, 2 mm).
μm), contains high concentrations of pigments, etc. The intermediate layer 21 blocks oxygen plasma and contains silicon (for example, a 0.2 μm thick SOG film). The upper resist film 12 is photosensitive (the same as that used in the single-layer resist method), and has a thin film thickness (for example, 0.5 μm) in order to obtain high resolution.

Next, the upper resist film 12 is exposed and developed to obtain an upper resist pattern 12A (see FIG. 2(b)). Next, the intermediate layer 21 is anisotropically etched using this upper resist pattern 12A as an etching mask (the etching gas is, for example, CF4), and the intermediate layer pattern 21A is etched using the upper resist pattern 12A as an etching mask.
(see Figure 2(c)). Thereafter, using the intermediate layer pattern 21A as an etching mask, the lower resist film 11 is anisotropically etched using oxygen plasma to obtain the lower resist pattern 11A, completing the desired three-layer resist pattern (see FIG. 2(d)). ). Note that since the upper resist pattern 12A does not have oxygen plasma resistance, it disappears when the lower resist film 11 is etched.

FIGS. 3(a) to 3(c) are schematic sectional views showing a second example of the conventional method in the order of steps. This method is an example of a two-layer resist method. First, a lower resist film 11 and an upper resist layer 31 are sequentially formed on the substrate 1 (see FIG. 3(a)).
) reference). The lower resist film 11 is the same as the first example described above. The upper resist film 31 contains silicon,
It has photosensitivity and oxygen plasma resistance, and has a thin film thickness (for example, 0.5 μm) in order to obtain high resolution.

Next, the upper resist film 31 is exposed and developed to obtain an upper resist pattern 31A (see FIG. 3(b)). Next, using the upper resist pattern 31A as an etching mask, the lower resist film 11 is anisotropically etched using oxygen plasma to obtain the lower resist pattern 11A, completing the desired two-layer resist pattern (FIG. 3(c)). reference).

[0009]

[Problems to be Solved by the Invention] However, in the first example, the process of such conventional patterning methods is complicated, and in the second example, photosensitive resists with sufficient oxygen plasma resistance cannot currently be obtained. There was a problem in that pattern shift was likely to occur during etching because there was no pattern.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a method for patterning a multilayer resist, which allows a highly accurate pattern to be obtained and which is a relatively simple process.

[0011]

[Means for Solving the Problems] According to the present invention, this object includes the steps of forming a lower resist film 11 on the surface of a substrate 1, and after forming an upper resist film 12 on the lower resist film 11. Expose and develop upper layer resist pattern 1
2A and the step of forming the upper resist pattern 12.
A Oxygen plasma blocking film 13 made of SiO2 etc. on the upper surface
selectively forming by diagonal sputtering, and forming a lower resist pattern 11A by anisotropically etching the lower resist film 11 by ECR plasma etching using the oxygen plasma blocking film 13 as a mask. This can be achieved by providing a patterning method characterized by including:

0012

[Operation] According to the present invention, inorganic materials such as silicon oxide, titanium, and titanium oxide, which have sufficient oxygen plasma resistance, are used as the etching mask for forming the lower resist pattern, so pattern shift is minimized. ,
Therefore, the pattern can be transferred with high precision. Furthermore, since this oxygen plasma blocking film is formed by diagonal sputtering after the upper resist pattern is formed, it is not necessary to provide an independent patterning process or a process to remove the film attached to excess areas. , so the process is relatively simple.

[0013]

EXAMPLE An example of the multilayer resist patterning method according to the present invention will be described with reference to FIG. Figure 1 (
a) to (d) are schematic cross-sectional views showing examples of the present invention in the order of steps. In the figure, 1 is a substrate, on the surface of which a thin film of aluminum or the like is formed. Reference numeral 11 denotes a lower resist film 11, which flattens steps on the surface of the substrate 1 and prevents light reflection from the surface of the substrate 1 during exposure, and is, for example, a novolak-based positive resist containing a high concentration of dye. . Reference numeral 12 denotes an upper resist film 12, which is photosensitive and is, for example, a novolac positive resist. 13 is an oxygen plasma blocking film, 11A is a lower resist pattern, 1
2A is an upper layer resist pattern.

First, a lower resist film 11 having a thickness of, for example, 2.0 μm is formed on the surface of the substrate 1 by spin coating. Next, this is heated at about 200°C (hard baking) to eliminate photosensitivity. Next, the lower resist film 11 is coated with a thickness of, for example, 0.5 μm by a spin coating method.
Form an upper resist film 12 (see FIG. 1(a)).
. After baking this at about 80° C., it is exposed to ultraviolet light and developed with an alkaline developer to obtain an upper resist pattern 12A (see FIG. 1(b)). Note that the lower resist film 11 is not dissolved in the developer and therefore is not patterned.

Next, a plasma blocking film 13 made of silicon oxide (SiO2) having a thickness of about 1500 Å, for example, is formed on the upper surface of the upper resist pattern 12A by diagonal sputtering (see FIG. 1(c)). At this time, the sputtering angle is selected so that silicon oxide does not adhere to the exposed lower resist film 11 (the substrate 1 is tilted, for example, by 1 to 10 degrees). After that, ECR (electron cyclot
By plasma etching (ron resonance), the lower resist film 11 is anisotropically etched with oxygen plasma to obtain a lower resist pattern 11A, and a desired multilayer resist pattern is completed (see FIG. 1(d)).

In the multilayer resist pattern thus obtained, the fine pattern formed on the upper resist film is accurately transferred to the lower resist film. The present invention is not limited to the above embodiments, but can be implemented with various modifications. For example, the inventor has confirmed that the present invention is effective even when titanium or titanium oxide is used instead of silicon oxide as an oxygen plasma blocking film.

[0017]

[Effects of the Invention] As explained above, according to the present invention,
It is possible to provide a multilayer resist patterning method that provides a highly accurate pattern and a relatively simple process, contributing to pattern miniaturization of semiconductor ICs.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the present invention in the order of steps.

FIG. 2 is a schematic cross-sectional view showing a first example of a conventional method in order of steps.

FIG. 3 is a schematic cross-sectional view showing a second example of a conventional method in order of steps.

[Explanation of symbols]

1 Semiconductor substrate 11 Lower resist film 11A Lower resist pattern 12, 31 Upper resist film 12A, 31A Upper resist pattern 13 Oxygen plasma blocking film 21 Intermediate layer film 21A Intermediate layer pattern

Claims (3)

[Claims] [Claim 1] A lower resist film (1) on a substrate (1).
1), forming an upper resist film (12) on the lower resist film (11), and exposing and developing the upper resist film (12) to form an upper resist pattern (12A). a step of selectively forming an oxygen plasma blocking film (13) on the upper surface of the upper resist pattern (12A);
A patterning method comprising the step of anisotropically etching the lower resist film (11) using a mask as a mask to form a lower resist pattern (11A). 2. The patterning method according to claim 1, wherein the oxygen plasma blocking film (13) is formed by an oblique sputtering method. 3. The patterning method according to claim 1, wherein the material of the oxygen plasma blocking film (13) is silicon oxide, titanium, or titanium oxide.