JPH02129917A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent deterioration of characteristics and development of under cut in a gate electrode by forming an insulating film formed on a surface of a tungsten gate electrode of a silicon oxide film and a silicon nitride film cover ing a peripheral thereof. CONSTITUTION:Anisotropic dryetching is performed for a tungsten electrode through reactive ion etching using sulfer hexafluoride gas by use of a mask which is constituted by a silicon oxide film 4 in contact with a surface of a tungsten gate electrode and a silicon nitride film 5 covering other sides of the silicon oxide film 4 which are not in contact with the tungsten gate elec trode. An insulating film thus formed on a surface of the tungsten electrode is a film of a silicon nitride film 5 and a silicon nitride film 7 which cover the silicon oxide film 4. According to this constitution, it is possible to prevent characteristic deterioration of a transistor and development of under cut at a gate electrode.

Description

[Detailed Description of the Invention] [Summary] Regarding the improvement of the gate electrode formation method when tungsten is used for the gate electrode/wiring, the characteristics of the transistor formed on the semiconductor substrate are not deteriorated, and undercuts do not occur in the gate electrode. An etching method for forming a tungsten gate electrode/wiring, the purpose of which is to provide a method for manufacturing a semiconductor device capable of etching a silicon oxide film in contact with a surface of a tungsten gate electrode, and the tungsten in the silicon oxide film. The structure includes a step of performing anisotropic dry etching of the tungsten electrode by reactive ion etching using sulfur hexafluoride gas using a mask made of a silicon nitride film that covers the other surface not in contact with the gate electrode. .

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor device, and particularly to an improvement in a method for forming a gate electrode when tungsten is used for the gate electrode/wiring.

2. Description of the Related Art As semiconductor devices have become more highly integrated and faster in recent years, there has been a demand for lower resistance electrodes or wiring materials.

As a countermeasure to this problem, high melting point metals are being used, and tungsten in particular is considered promising because it is thermally stable and has excellent chemical resistance.

On the other hand, as higher integration requires the formation of electrodes and interconnections that are more faithful to the mask pattern, tungsten etching treatment has been replaced by anisotropic active ion etching (hereinafter referred to as "active ion etching") using a silicon oxide film as a mask. R,1
,E, is abbreviated as . ).

However, in anisotropic R,1,E, which uses tungsten as an electrode material and uses sulfur hexafluoride gas with a silicon oxide film as a mask, an undercut occurs in the tungsten electrode.

Under the above circumstances, there is a need for a method of manufacturing a semiconductor device that can form a tungsten electrode by etching without causing an undercut in the tungsten electrode.

[Conventional technology]

A conventional manufacturing method for forming a gate electrode of a semiconductor device will be explained in order of steps with reference to FIGS. 2 and 3.

FIG. 2 is a side sectional view showing a conventional manufacturing method for forming a polysilicon gate electrode of a semiconductor device in order of steps.

First, an insulating film and a resist film are laminated on the entire surface of the semiconductor substrate 11 on which a gate oxide film 12 and a polysilicon film 13 are formed, and as shown in FIG. The insulating film 14 is patterned as shown in the figure using this pattern as a mask.

Next, as shown in FIG. 2(b), using this insulating film 14 as a mask, the polysilicon film 13 is etched with R, 1, E, and the semiconductor substrates on both sides of the polysilicon film 13 are etched.
An n'' layer 11a is formed in the semiconductor substrate 11 by implanting ions into the semiconductor substrate 11.

Then, as shown in FIG. 2 (C1), the resist film 16 is removed and a silicon nitride film 7 is formed on the entire surface.

After that, Figure 2! As shown in d), the silicon nitride film 17 is etched using R, 1, E to form a side wall of the silicon nitride film 17 on the side wall of the polysilicon film 13, and both sides of the side wall of the silicon nitride film 17 are etched. Ions are implanted into the semiconductor substrate 11 to form the n' layer 11b in the semiconductor substrate 11.

Finally, as shown in Figure 2 (8), a PSG film 1 is applied to the entire surface.
8 are formed, electrode extraction windows are formed in the PSG film 18, and a source electrode 19 made of aluminum or the like, a gate electrode 20 . After forming the drain electrode 21, the manufacturing of the semiconductor device is completed.

However, tungsten, a low resistance material, is used instead of polysilicon as the gate electrode, and R with sulfur hexafluoride gas is used. When anisotropic etching is performed using E, the second
In the process shown in Figure ('b), when a silicon oxide film is used as the insulating film 14, an undercut occurs on the tungsten electrode, and when a silicon nitride film is used as the insulating film 14, an undercut occurs on the tungsten electrode. Although this does not occur, it is difficult to use tungsten as a gate electrode because the characteristics of the transistor formed on the semiconductor substrate 11 deteriorate.

[Problem to be solved by the invention]

In the conventional manufacturing method for forming the gate electrode of a semiconductor device described above, tungsten, which is a low resistance material, is used as the material of the gate electrode, and R, 1
．． When anisotropic etching is performed using E, when a silicon oxide film is used as the insulating film on the surface of the gate electrode, the oxygen in the silicon oxide film and the sulfur hexafluoride gas are mixed as shown in Figure 3(a). Since it combines with sulfur to become sulfur dioxide (SO2) and vaporizes, the sulfur that protects the side walls of the tungsten electrode disappears, and the tungsten electrode is etched by fluorine, causing an undercut in the tungsten electrode. In addition, if a silicon nitride film is used, see Figure 3).
As shown in , the sulfur in the sulfur hexafluoride gas protects the side walls of the tungsten electrode, so no undercut occurs on the tungsten electrode, but a large stress is generated between the silicon nitride film and the tungsten electrode due to thermal history. There was a problem in that the characteristics of the transistor formed on the semiconductor substrate deteriorated.

In view of the above-mentioned circumstances, the present invention aims to provide a method for manufacturing a semiconductor device that can prevent the characteristics of a transistor formed on a semiconductor substrate from deteriorating and undercut the gate electrode from occurring. It is.

[Means to solve the problem]

In the method for manufacturing a semiconductor device of the present invention, in the etching method for forming a tungsten gate electrode/wiring, a silicon oxide film in contact with the surface of the tungsten gate electrode;
R using sulfur hexafluoride gas using a mask made of a silicon nitride film that covers the other surface of this silicon oxide film that is not in contact with the tungsten gate electrode; 1. The structure includes a step of performing anisotropic dry etching of the tungsten electrode by E.

[Effect]

That is, in the present invention, in the etching method for forming tungsten gate electrodes and wiring, a mask is used to cover the silicon oxide film in contact with the tungsten gate and the other surface of this silicon oxide film that is not in contact with the tungsten gate with a silicon nitride film. R using sulfur hexafluoride gas, 1. E.

Since the tungsten electrode is dry etched by the method, the side wall of the tungsten electrode is protected by the sulfur of the sulfur hexafluoride gas and no undercut occurs.

Since most of the surface of the tungsten electrode is covered with a silicon oxide film, no stress is generated between the silicon oxide film and the tungsten electrode due to thermal history, unlike when the surface is covered with a silicon nitride film. It becomes possible to prevent deterioration of characteristics of a transistor formed on a semiconductor substrate.

(Example) An example of the present invention will be described below in order of steps with reference to FIGS. 1 and 2.

First, as shown in FIG. 1(a), a silicon oxide film 4 with a film thickness of 1,000 and a film thickness of A silicon nitride film 5 of i, ooo is laminated, a resist film is formed on the surface thereof, and the resist film 6 is patterned by photolithography.

Next, using the patterned resist film 6 as a mask, as shown in FIG. 1 (bl), the silicon nitride film 5 and the silicon oxide film 4 are patterned, and the resist film 6 is removed.

Next, a silicon nitride film of I ¥1,000 was formed on the entire surface, and R, 1. Then, the silicon nitride film is anisotropically etched using E to form a side wall of the silicon nitride film 7 on the side walls of the silicon nitride film 5 and the silicon oxide film 4, as shown in FIG. 1(C).

Thereafter, as shown in FIG. 1(d), the silicon oxide film 4
R, 1 using sulfur hexafluoride gas (SF6) using the silicon nitride film 5 and silicon nitride film 7 covering this as a mask.
．． The tungsten layer 3 is anisotropically etched using E to form a tungsten electrode.

When a silicon nitride film is formed on the entire surface, the insulating film 14 in FIG. This results in a state equivalent to that in which the polysilicon film 13 has become the tungsten layer 3, and subsequent steps can be used to manufacture a semiconductor device using the same steps as the conventional manufacturing method.

In this way, the insulating film formed on the surface of the tungsten electrode is a film in which the silicon oxide film 4 is covered with the silicon nitride film 5 and the silicon nitride film 7.
is formed around the tungsten electrode, so that while oxygen does not come out from the silicon oxide film 4, the sulfur of the sulfur hexafluoride gas protects the side wall of the tungsten electrode and no undercut occurs.

Most of the surface of the tungsten electrode is in contact with the silicon oxide film 4, so no stress is generated between the silicon oxide film and the tungsten electrode due to thermal history, thereby preventing deterioration of the characteristics of the transistor formed on the semiconductor substrate. It becomes possible to do so.

FIG. 2 is a side sectional view showing a conventional manufacturing method for forming a polysilicon gate electrode of a semiconductor device in the order of steps; FIG. 3 is a side sectional view illustrating problems in the conventional manufacturing method of a semiconductor device; Effects] As is clear from the above explanation, according to the present invention, it is formed on the surface of the tungsten gate electrode! f! By forming the I edge film from a silicon oxide film and a silicon nitride film surrounding the silicon oxide film, the characteristics of a transistor formed on a semiconductor substrate are not deteriorated and undercuts do not occur in the gate electrode. It is possible to provide a method for manufacturing a semiconductor device that can be expected to significantly improve reliability.

shows.

is a semiconductor substrate, is the gate oxide film, is a tungsten layer, is silicon oxide film, is silicon nitride film, is a resist film, is silicon nitride film,

[Brief explanation of drawings]

FIG. 1 is a side cross-sectional view showing one embodiment of the present invention in the order of steps.
) Formation of a side wall of the C1 silicon nitride film (7) Side sectional drawing showing an embodiment of the present invention in order of process Figure 1 (Part 2) Formation of a side wall of C1 silicon nitride film (7)
Figure (Part 1) Patterning of polysilicon 11 (13) and n-layer (
Formation of lla) Side cross-sectional drawing showing the manufacturing method for forming a conventional polynolycon gate electrode of a semiconductor device in order of process 2
Figure (Part 1) + (11 Formation of side wall of silicon nitride ff1 (17) and n° layer (11,) formation (81 Formation of source electrode, gate electric machine, drain 'Wi electrode) Polysilicon of conventional semiconductor device Side cross-sectional book showing the manufacturing method for forming gate electrodes in the order of steps Figure 2 (Part 2)
) When the insulating film on the surface of the gate electrode is a silicon oxide film, Figure 3 is a side cross-sectional view explaining the problems of the conventional manufacturing method of semiconductor device I.

Claims (1)

[Claims] An etching method for forming a tungsten gate electrode/wiring, comprising a silicon oxide film in contact with the surface of the tungsten gate electrode and another surface of the silicon oxide film not in contact with the tungsten gate electrode. A method for manufacturing a semiconductor device, comprising the step of performing anisotropic dry etching of a tungsten electrode by reactive ion etching using sulfur hexafluoride gas using a mask made of a covering silicon nitride film.