JPH01214025A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enhance the uniformity of an etching rate over a face by a method wherein, when a plasma nitride film is to be etched by making use of a resist as a mask, a reactive ion etching is performed by using a gas system where a specific quantity of N2 has been added to CF4 in a specific vacuum. CONSTITUTION:When a semiconductor device is to be manufactured after a reactive ion etching process of a plasma nitride film 2 by making use of a resist 3 as a mask, the reactive ion etching process is executed by using a gas system 4 where 10% or less of N2 has been added to CF4 in a vacuum of 10 Pa or less. For example, the plasma nitride film 2 is grown on the surface of a substratum 1; the resist mask 3 of a required pattern is formed on it; the reactive ion etching process is executed in said manner. By this setup, a reduction in an F radical and the deposition due to copolymerization of a resist component and a gas component are made small; as a resist, an etching rate is lowered even in the central part of a wafer where an ion shock is small; the etching rate becomes definite irrespective of the etching time; the uniformity over a face is made excellent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of etching a plasma nitride film using a reactive ion etching method.

[Conventional technology]

Generally, as a method for forming patterns of various films in the manufacturing process of semiconductor devices, a method is used in which a mask is formed in the desired pattern on the film to be patterned, and the film is etched using the mask. ing. Conventionally, when patterning a plasma nitride film using this type of method, a patterned resist is used as a mask.
A method of etching this using a CF, +Hz gas system or an active ion etching method is used.

For example, an example of the conventional method is shown in Figs. 2(a) to (C).
The progress of etching is shown schematically and in chronological order.

That is, a resist 3 having a desired pattern is provided on a plasma nitride film 2 formed on a base substrate 1, and a CF4
+)(, Etching is performed by irradiating plasma 4.

[Problem to be solved by the invention]

In the conventional method described above, etching is performed while depositing a copolymer 5 of a resist component and a gas component onto the plasma nitride film 3, as shown in FIGS. 2(b) and 2(C). C.F.

Since F radicals, which are the etchant for the plasma nitride film, are reduced by adding F, there is a problem that the etching rate in the center of the wafer where there is less ion bombardment decreases and the in-plane uniformity deteriorates.

In other words, as shown in Fig. 4, since a gas system of CF4 +) is used, a decrease in F radicals and a deposition of a copolymer of the resist component and the gas component occur, and the etching rate is determined by the etching time. As the length increases, the etching rate rapidly decreases.Furthermore, since this decrease in etching rate is significant at the center of the wafer, there is a problem that the in-plane uniformity of the etching rate becomes extremely poor.

An object of the present invention is to provide a method for manufacturing a semiconductor device that can improve the in-plane uniformity of etching rate.

[Means to solve the problem]

In the semiconductor device manufacturing method of the present invention, when etching a plasma nitride film using a resist as a mask, reactive ion etching is performed using a gas system containing CF with 10% or less N2 added at a vacuum level of 10 Pa or less. Is going.

[Effect]

In the method described above, CF is applied at a vacuum degree of 10 Pa or less.

By using a gas system to which 1θ% or less of N2 is added, F radicals, which are etchants for the plasma nitride film, are increased, and deposition due to copolymerization of resist components and gas components is suppressed.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1(a) and 1(b) are longitudinal cross-sectional views of a plasma nitride film subjected to reactive ion etching according to the present invention. As shown in FIG. 2A, a plasma nitride film 2 is grown on the surface of a base 1, and a resist mask 3 having a desired pattern is formed thereon. Then, a gas system 4 in which 10% or less N2 was added to CF a at a vacuum degree of 10 Pa or less
Reactive ion etching is performed using

As a result, uniform etching can be performed within the wafer surface, as shown in FIG. 2(b).

That is, FIG. 3 shows the etching rate when a plasma nitride film is subjected to reactive ion etching according to the present invention. CF at a vacuum level of 10 Pa or less, to 10
% or less of N2 is used, there is less F radical' and less deposition due to copolymerization of the resist component and gas component.As a result, the etching rate is reduced even in the center of the wafer where there is less ion bombardment. The etching rate is constant regardless of the etching time, and the in-plane uniformity is good.

Here, if etching is performed at a vacuum degree of 10 Pa or more, it becomes difficult to maintain anisotropy and side etching is likely to occur. Furthermore, if N2 is added in an amount of 10% or more, the etching rate will decrease, so care must be taken.

(Effects of the Invention) As explained above, the present invention uses a gas system in which 10% or less N2 is added to CF at a vacuum degree of 10 Pa or less.
Since active ion etching is performed on the plasma nitride film using a resist as a mask, F radicals, which are the etchant of the plasma nitride film, are increased, and deposition due to copolymerization of resist components and gas components is suppressed, so etching time is This method has the effect of maintaining a constant etching rate and improving in-plane uniformity by nearly 20 times compared to conventional methods.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are process cross-sectional views for explaining the method of the present invention, FIGS. 2(a) to (C) are cross-sectional views showing the conventional method in order of process, and FIG. 3 is a process cross-sectional view for explaining the method of the present invention. FIG. 4 is a diagram showing the etching rate versus etching time in the conventional method. DESCRIPTION OF SYMBOLS 1... Base, 2... Plasma nitride film, 3... Resist mask, 4... -CF, +H, plasma, 5...
Deposition. Figure 1 Figure 2 + 11! i j'″jjJI1

Claims (1)

[Claims] 1. In a semiconductor device manufacturing method that includes a step of reactive ion etching of a plasma nitride film using a resist as a mask, CF_4 is etched with a vacuum of 10 Pa or less.
1. A method for manufacturing a semiconductor device, characterized in that reactive ion etching is performed using a gas system to which N_2 is added in an amount of % or less.