JPH0320745A - Resist pattern forming method - Google Patents

Abstract

PURPOSE:To reduce ruggedness of the ends of a resist and to enable fine working on a substrate having high level differences by adding a Si compound into the gas to be used for the reactive ion etching. CONSTITUTION:The resist 4 is applied on the substrate having high level differences 5 formed by laminating SiO2 2 and Al 3 on the Si substrate 1 so as to almost flatten the surface, and a desired pattern is printed through a photomask 6. Then, the surface is exposed to gaseous hexamethyldisilazane (HMDS) and like, while heating the substrate 1, to form a sililated layer 7 on the exposed parts of the resist 4. The resist 4 is dry developed by the reactive ion etching using oxygen having a desired amount of HMDS added, to form a resist pattern 8, and an Al printed circuit pattern 9 is formed by treating it by the dry etching process.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Application Fields The present invention relates to microfabrication technology used in the VLSI manufacturing process, particularly resist pattern formation technology.

<Prior Art> Microfabrication of VLSIs is mainly performed using a so-called IJ lithography technique (photolithography technique) using a reduction projection exposure apparatus. With the increasing integration of VLSIs, there is a need to form submicron patterns, which is at the very limit of the resolution of reduction projection exposure apparatuses. Recently, LSIs have become three-dimensional in order to improve the degree of integration, and as a result, it has become necessary to form fine patterns on substrates with high height differences (1 μm level).

A three-layer resist process is known as a method for forming fine patterns on high-level differences, but it has the disadvantage that the process is complicated. To solve this problem, a silylated resist process has been developed and has been shown to be effective for processing at the 3000-inch micron level.

Problems to be Solved by the Invention On the other hand, the disadvantage of the untreated resist process is that the edges of the pattern have large irregularities, which is a problem when this process is applied to the formation of 0.5μ melons or smaller. It has become. The mechanism of occurrence of unevenness at the edge of Bakun is as follows.
It is still not clear, and in the past, improvements have been made to the composition of resists and the conditions for selective diffusion of silicon compounds. The present invention solves the problem of unevenness at the edge of a resist film subjected to a silylated resist process by improving a dry development method. That is, the present invention realizes a silylated resist process with less unevenness at the edge of a pattern by improving the dry development method, and improves O.I. S It enables processing of microns or less.

Means for Solving the Problems> The method for forming a resist pattern of the present invention includes a step of applying a photoresist on a substrate, a step of printing a mask pattern onto the photoresist using an exposure device, and a step of printing a mask pattern on the exposed portion of the resist. A method for forming a resist pattern, comprising the steps of selectively diffusing a compound containing at least silicon in its molecules, and selectively removing unexposed portions of the resist by reactive ion etching mainly using oxygen and dry-developing the resist. The method is characterized in that a compound containing at least silicon in its molecules is added to the gas for dry development by reactive ion etching.

Examples> Hereinafter, HMDS (hexamethyldisilazane (CHs)
Taking as an example a silylated resist process using Si(NH)Si(CH3)a ) as a silicon diffusion source,
The details of the present invention will be explained.

FIG. 1 is a cross-sectional view of the silylated resist process.

Here, a process for forming a resist pattern on aluminum on a high-step substrate will be described as an example (aluminum is formed to a thickness of 1.0 μm on a step of 1.0 μm wide). First, a resist is applied onto the substrate and baked to remove the solvent. In order to perform dry etching of aluminum with high precision, a resist thickness of 1.0 μm or more is required. Since the resist on the step is applied almost flat, as shown in FIG. 1(a), the resist film thickness on the concave portion is 2.0 μm, and the resist film thickness on the convex portion is 1.0 μm. Among them, in Fig. 1 0), 1 is a Si substrate, 2 is a Si02
, 3 is aluminum, and 4 is resist. 1 and 5 are step portions.

A mask pattern is printed onto this resist using a reduction projection exposure device. As a result of the exposure, the photosensitive groups in the portions corresponding to the resist pattern are decomposed, as shown in FIG. 1(b). The degree of decomposition of photosensitive groups is greater on the resist surface where the light intensity is high. Among them, 6 in FIG. 1(b) is a photomask.

Next, as shown in FIG. 1(C), the substrate is
It is exposed to gaseous HMDS while maintaining the temperature at about 0.000C, and silicon in I{MDS is selectively diffused into the region where the photosensitive group has been decomposed (silylation). By optimizing the exposure amount and diffusion conditions, it is possible to diffuse silicon into a portion approximately 0.2 μm from the resist surface where the rate of photosensitive group decomposition is large.

In the WIJI diagram (C), 7 is a silylated layer.

Subsequently, the substrate is processed by reactive ion etching using oxygen gas. The region where silicon is diffused is oxidized by oxygen plasma to form silicon oxide, which serves as an etching-resistant mask. On the other hand, regions where silicon is not diffused are etched by reacting with oxygen radicals and oxygen ions, similar to a normal resist. As a result of the above reaction, the resist pattern is dry developed and a resist pattern 8 is formed on the high-step substrate (FIG. 1(d)). By applying the conventional aluminum dry etching method using this resist pattern, the desired aluminum wiring pattern 9 can be formed (Fig. 1 (e), (f)).
.

When this process is applied, the unevenness of the resist end face is
The maximum door size on one side is about 0.1μ. This unevenness is reflected in the processed shape of the aluminum, and the side surfaces of the aluminum wiring become uneven. Such unevenness on the side surface of the wiring causes a local increase in current density, resulting in a decrease in wiring reliability.

The present inventor investigated the mechanism of occurrence of unevenness on the end face of the resist by observing and analyzing in detail the side surface of the resist after dry development. As a result, it has been found that wrinkles are formed on the side surfaces of the resist during dry development, and that these wrinkles are the main cause of unevenness on the end faces of the resist. Furthermore, analysis of wrinkles on the side surface of the resist revealed that silicon was observed and that most of the wrinkles could be removed with an aqueous solution containing hydrofluoric acid. From these results, the inventor estimated that the wrinkles on the side surface contained silicon oxide. Judging from the conditions of the silylation process in the experimental example, it is unlikely that the silicon penetrates deeply into the resist before ethoching. Therefore, it is considered that silicon oxide was attached to the side surfaces during etching. Based on the above results, the present inventor estimated the mechanism of generation of wrinkles on the sidewall as follows.

The source of silicon oxide formed on the sidewalls is silicon diffused into the exposed area, which is ejected into the gas phase by ion bombardment during dry development and adheres to the sidewalls. Silicon oxide adhering to the bottom surface is knocked out by ion bombardment, resulting in silicon oxide gathering on the sides! It's easy to do. It is believed that this silicon oxide adheres non-uniformly to the side surfaces by some mechanism. The regions to which silicon oxide is not attached are laterally etched by oxygen radicals, but the regions to which silicon oxide is attached are not etched laterally, and as a result, wrinkles are formed on the side surfaces of the resist.

Based on the above model, the inventor of the present invention has developed D1 by continuously supplying sufficient silicon to protect the sidewalls from the gas phase.
The idea was to uniformly form a protective film against lateral etching using silicon oxide on the sidewalls. By uniformly forming the sidewall protective film, wrinkles on the b1 side surface can be reduced, and as a result, unevenness at the end of the resist pattern can be reduced.

As a supply source for supplying silicon in a vapor phase during dry development, it is conceivable to supply a compound containing at least silicon in its molecule in a vapor phase.

Specific compounds include HMDS (hexamethyldisilaza7(cHa)asr(NH)Si(CH8)3),
Possible materials include SiH4, SiCl4, and SiF4. Table 1 shows the results when dry development was performed by adding HMDS to oxygen. The expected wrinkles on the sides of the resist disappeared, and the unevenness on the end faces of the resist was also reduced. It is easily inferred that a similar effect can be achieved by supplying a compound containing at least silicon in the molecule in the gas phase.

Effects of the Invention> By using the dry development method of the present invention, a high-quality resist pattern with less unevenness at the edges of the resist could be formed. As a result, it has become possible to form highly reliable fine metal wiring with high precision.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the silylated resist process. Explanation of symbols 1sSi substrate, 2: Si02, 3: Aluminum, 4: Resist, 5: Step portion, 6: Photomask, 7
: silylated layer, 8: resist pattern, 9: aluminum wiring. Other conditions

Claims (1)

[Claims] 1. A step of applying a photoresist onto a substrate, a step of baking a mask pattern onto the photoresist using an exposure device, a step of selectively diffusing a compound containing at least silicon in its molecules into the exposed part of the resist, and a step of mainly using oxygen. A method for forming a resist pattern includes a step of selectively removing unexposed portions of the resist by reactive ion etching using reactive ion etching and dry development. A method for forming a resist pattern, the method comprising adding a compound containing.