JPH0496327A - Etching method - Google Patents

Abstract

PURPOSE:To facilitate a control of shaping a tapered longitudinal section, by repeating alternately a first process for removing selectively and isotropically only the unnecessary part of an etching layer and a second process for depositing a material, different from the etching layer, to form a sidewall on the side part of a mask pattern in such a manner that the material deposits even in the undercut part removed in the first process. CONSTITUTION:After forming a sidewall 4a, an etching gas is introduced, and only an Al layer 2 is removed selectively and isotropically by using a resist pattern 1 and the sidewall 4a as masks. Moreover, this removing of the Al layer 2 is performed in its thickness direction and partially. Then, a deposition gas is introduced again, and by sputter etching, a sidewall 5a is formed on the side part of the sidewall 4a in such a manner that it extends into the undercut part of the Al layer 2. Thereafter, the etching gas is introduced again, and via a process for forming a thin film, performed are repeatedly the process for shaping the thin film into a sidewall and the process for etching the Al layer selectively, partially and in isotropic way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an etching method used in the manufacturing process of semiconductor devices, particularly for etching a metal layer such as A1, a semiconductor layer such as polycrystalline silicon, a semiconductor layer such as SiO2, etc. The present invention relates to an etching method for removing an insulating layer in a tapered shape.

[Conventional technology]

Such taper etching method (7);
■Method for controlling the shape of resist pattern (Unexamined Japanese Patent Publication No. 6)
4-1.5933), ■ method of depositing a protective film on the side wall and etching it from scratch (Japanese Patent Application Laid-Open No. 1999:1-127).
687 (see Japanese Patent Laid-Open No. 63-233535), and (2) a method in which anisotropic etching and thin film deposition are performed alternately (see Japanese Patent Laid-Open No. 63-233535).

[Problem to be solved by the invention]

17 However, in the dry etching method using the recession of the resist pattern described in (1) above, it is necessary to form one resist pattern thicker than usual, and as the line width etc. become thinner, high precision etching becomes difficult. Become. Moreover, the resist pattern may disappear during etching at the upper part of the step where the thickness of the resist pattern is thinner, and unnecessary portions may be etched.

In the method of controlling the shape of the resist pattern described in ■ above,
A new process must be added to control the shape of the resist pattern, and the process becomes complicated accordingly. Furthermore,
Since the etching shape largely depends on the shape of the resist pattern, it is difficult to respond to miniaturization of elements.

In the method (2) above, in which etching is performed while depositing a protective film on the sidewalls, the reaction between the deposition of the protective film and etching that takes place in plasma is complex and not fully understood, so controlling the taper angle requires experience. I have no choice but to rely on it. Therefore, when changing the gas system or experimental conditions, it is difficult to predict in advance the results that will be obtained.

In the method (2) above, in which anisotropic etching and thin film deposition are performed alternately, there is a step of anisotropically etching unnecessary portions of the layer to be etched, and a step of removing unnecessary portions of the thin film and leaving them as sidewall spacers. Both are performed by anisotropic etching in which physical removal of unnecessary portions is dominant. Therefore, when the unnecessary portion of the layer to be etched is removed after the unnecessary portion of the thin film is removed, the sidewall spacer formed from the thin film is also etched and retreated. Therefore, it is difficult to control the cross-sectional shape such as the taper angle.

Therefore, in view of the above-mentioned circumstances, an object of the present invention is to provide an etching method that allows easy control of the cross-sectional shape such as the taper angle.

[Means to solve the problem]

In order to achieve the above object, the etching method according to the present invention includes a first step in which unnecessary portions of the layer to be etched are partially removed in the same direction, and a first step in which unnecessary portions of the layer to be etched are removed in the same direction. and a second step of forming the side wall extending to the undercut portion made of a material different from that of the layer to be etched, and is characterized in that the first step and the second step are alternately repeated.

[Effect]

By doing this, in the process of removing unnecessary portions of the layer to be etched, only the unnecessary portions of the layer to be etched are partially removed without etching the sidewalls.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG.

FIG. 1 shows an aluminum layer (hereinafter referred to as A) obtained by applying the present invention.
, 17 layers), A
FIG. 3 is a cross-sectional view showing how one layer is tapered etched in the order of steps.

Figure (a) shows a cross section before etching, and shows the A1 layer 2 formed on the semiconductor substrate 3 as a layer to be etched.
A resist pattern 1 is formed on the surface.

According to the etching method according to the present invention, this AfI layer 2 is tapered etched as follows.

First, a deposition gas such as CHCg3 is introduced to form a thin film 4 on the Al1 layer 2 from above the resist pattern 1, as shown in FIG. 2B. Next, a gas such as B1113 is introduced, and the thin film 4 is removed approximately perpendicularly to the surface of the A1 layer by sputter etching, which is a physical removal method. As a result, the thin film 4 is removed leaving the portions formed on the sides of the resist pattern 1.
The portion left on the side becomes the side wall 4a (see figure (C)). After the side wall 4a is formed in this way, 0 g
An etching gas such as No. 2 is introduced, and by the chemical action of the etching gas, only the A1 layer 2 is selectively and uniformly removed using the resist pattern 1 and the side wall 4a as a mask (see FIG. 2(d)). Moreover, this A9 layer 2 is removed partially in the thickness direction of this layer. And again, C
A deposition gas such as HCl13 is introduced, and the same figure (e
), a thin film 5 is formed equidirectionally on the A1 layer 2 from above the resist pattern 1 and the side wall 4a. So [7
1. This thin film 5 was formed by sputter etching.
1. Leave the portion formed on the side of resist pattern 1.
physically remove it. As a result, A is attached to the side of the side wall 4a.
After forming the side wall 5a on the side of the resist pattern 1 with L2 in this way, the side wall 5a that wraps around to the undercut part of layer 2 is obtained (see (f) in the same figure).
! Etching gas such as No. 2 is introduced, and by the chemical action of the etching gas, only the Af1 layer 2 is selectively, partially and uniformly removed from the sidewall 4a and sidewall 5a@mask (1/cyst pattern). (see (g)). 12. After the above-mentioned thin film formation step, there is a step of shaping the thin film into a side wall (see (e) and (f) in the same figure), and selectively forming the A1 layer.
By repeating the partial and isodirectional etching process (see (g) in the same figure), one layer 2 can be removed in a tapered shape.

[7] The shape of the taper angle of the side surface of the A1 layer 2 left on the semiconductor substrate 3 depends on the deposition rate of the thin film that will become the sidewall, the etching rate of the thin film formed by sputter etching, and the elastin brake of the Ag layer. By appropriately setting and changing the cycles of each process (thin film forming process, sputter etching process, and A1 layer etching process), a desired taper angle and desired shape can be obtained.

In addition, the above 1. In the drawings used to explain the embodiments, the thickness of the thin film and sidewalls and the depth to which the Ag layer is removed in one etching process are exaggerated to make it easier to understand the present invention.1. ing. For this reason, the Ap9 layer 2 side left on the semiconductor substrate 3J2 is expressed as uneven, but by making the cycle of each process sufficiently short, the side surface of the A1 layer 2 It is a Noh performance that has a smooth finish.

〔Effect of the invention〕

As explained below, according to the etching method of the present invention, in the step of removing unnecessary portions of the layer to be etched, only the unnecessary portions of the layer to be etched are selectively removed. Side walls are not etched. Therefore, the taper angle and cross-sectional shape of the layer to be etched can be easily controlled. In addition, since such shape control can be performed by adjusting the thickness of the sidewall, the shape can be controlled almost unaffected by the shape of the resist pattern.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing how a layer to be etched is etched in the order of steps in the etching method according to the present invention. ]...Resist pattern, 2...A1 layer as a layer to be etched, 3...Semiconductor substrate, 4...Thin film, 4a
... Side wall, 5... Thin film, 5a... Side wall.

Claims (1)

[Scope of Claim] An etching method for selectively removing unnecessary portions of a layer to be etched with a mask pattern formed on its surface, the method comprising: selectively, partially, etc. removing only the unnecessary portions of the layer to be etched; A second step includes forming a sidewall on the side of the mask pattern that wraps around to the undercut portion removed in the first step using a material different from that of the layer to be etched. . An etching method, characterized in that the first step and the second step are alternately and repeatedly carried out.