JPS59113647A - Formation of undercut shape at multilayer structure of resist material - Google Patents

Abstract

PURPOSE:To enable to form an undercut of arbitrary shape by changing the baking temperature at the first layer formation time and the upper layer formation time of a multilayer resist layer by a method wherein the change of sensitivity to exposure of a resist material according to the baking temperature thereof is utilized using the same resist material. CONSTITUTION:A positive type photo resist material is applied on a semiconductor substrate 1 to form a resist layer 12, and baking is performed thereto at a high temperature to form a high sensitive first resist layer 12a. Then the positive type resist material the same with the first layer is applied on the first resist layer 12a, baking is performed thereto at the usual temperature, and a second resist layer 13 is formed to complete a multilayer resist layer. Accordingly, undercut shape can be changed delicately according to the heat-treating temperature of the lowest layer by the simple process, and width of a metal fine pattern to be formed using the method thereof can be changed arbitrarily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method and trap for forming an aledar cut shape in a multilayer structure of resist material for, for example, microfabrication by a lift-off method in the manufacturing process of semiconductor devices.

[Prior art]

FIGS. 1(a) to 1(d) are cross-sectional views at various stages of a conventional method of forming a fine pattern using an undercut shape of a resist. In this traditional method, first,
A first positive resist (referred to as positive resist) layer (2) is coated and baked on a semiconductor substrate (1) such as silicon, and then a second positive resist layer (3) is formed on top of it. The first step is to form the coating and perform baking.
Figure (a) A multilayer structure shown in K is formed. At this time, the first
The positive resist layer (2) is the second positive resist layer (3)
Use a resist material with higher sensitivity. Next, by exposing this to an electron beam, light, etc., and performing a development process, an undercut-shaped opening (4) can be obtained in the resist material as shown in FIG. 1(b). Subsequently, as shown in FIG. 1(c) K, metal is deposited from the entire upper surface to expose the metal layer (5) on the second resist layer (3) in the opening (4). A finely patterned metal layer (5a) is formed on a semiconductor substrate (1). After that,
By removing both resist layers (2) and (3), a fine pattern metal layer (
Only 5a) can remain on the semiconductor substrate (1).

However, the conventional method described above uses two different types of resist materials, and due to various constraints, it is difficult to combine resist materials with various sensitivities, and therefore the combinations of resist materials that can be used are limited. is,
This method has disadvantages in that it is not possible to form an arbitrary undercut shape in the resist layer, and it is not possible to use a highly sensitive second resist material.

[Summary of the invention]

This invention was made in view of the above points, and uses the same resist material to form a multilayer structure, and takes advantage of the fact that the exposure sensitivity changes depending on the baking temperature. [Embodiment of the Invention] Figures 2 (a) to (d) show the formation of a multilayer resist layer in this invention. FIG. 3 is a cross-sectional view at each stage showing an example of the method. First, on the semiconductor substrate (1) shown in FIG. 2(a),
As shown in Fig. 2(b), a resist layer (1'4) is formed by applying a positive resist material, and this is baked at the same temperature as shown in Fig. 2(tc). a)
As shown in , a positive resist material identical to that of the first layer is applied on the first resist layer (12a) and baked at a normal temperature to form a second resist layer θ barrel. Complete the multi-layer resist layer.

FIGS. 3(a) and 3(b) are cross-sectional views showing two examples of undercut shape formation according to the present invention, and FIG. 3(a)
Figure 3(b) shows the first resist layer (12a) baked at a relatively low temperature, and the second resist layer (12b) baked at a relatively high temperature, exposed and developed under the same conditions. The one baked at a high temperature has a higher exposure sensitivity, so the undercut in Figure 3(b) is larger. Figure 3 ((ri) and (d) are respectively Figure 3 (a) + (
Using the resist shape of b), a fine pattern metal layer (5a
).

(5b) is shown, and in this way it is possible to form a fine pattern with any width.

[Effects of the Invention] As explained above, in this invention, the same resist material is used for the bottom and top resist layers, and the bottom layer is heat-treated at a higher temperature than other layers to increase the exposure sensitivity.
This multilayer resist layer is exposed to light.

Since the undercut shape is formed through development, the process is simple, and the undercut shape can be subtly changed depending on the heat treatment temperature of the bottom layer. Using this, the width of the fine metal pattern formed can be adjusted arbitrarily. It can be changed.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view at each stage showing a conventional method of forming a fine pattern using an undercut shape of a resist, and Fig. 2 (a) to fd) show an example of the method of forming a multilayer resist layer according to the present invention. Cross-sectional views at each stage shown;
FIG. 3 is a sectional view showing two examples of undercut shape formation according to the present invention and a state in which a finely patterned metal layer is formed using them. In the figure, (1) is the substrate, (1) is the first resist layer, (12a) and (12b) are the first resist layer after heat treatment, and θ field is the second resist layer. The same symbols in the middle indicate the same or equivalent parts.
Nobuo Kuzu - (1 other person) Asahi 0

Claims (2)

[Claims] (1) When forming a multilayered resist layer on a substrate, a first resist layer is formed on the substrate, heat-treated at a required temperature, and then the first resist layer is formed on the substrate. By forming the remaining resist layers with the same resist material, the exposure sensitivity of the first resist layer can be made larger than the exposure sensitivity of the remaining resist layers, and the resist layer of the multilayer structure formed in this way can be improved. A method for forming an undercant shape in a multi-m structure of a resist material, the method comprising forming an undercut by subjecting the resist material to a required pattern of exposure and development. (2) A method for forming an undercut shape in a multilayer structure of a resist material according to claim 1, characterized in that a positive resist material is used as the resist material. (3) A method for forming an undercut shape in a multilayer structure of a resist material according to claim 1 or 2, characterized in that a photoresist material is used as the resist material. (4) A method for forming an undercut shape in a multilayer structure of a resist material according to claim 1 or 2, characterized in that an electron beam resist material as a resist material is subjected to rough exposure with an electron beam. .