JPH03276633A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To highly precisely form a fine gate electrode layer free from short- circuiting, by quickly eliminating poly silicon residue generated by anisotropic etching, without damaging a substrate, by using isotropic etching. CONSTITUTION:A resist layer 14 is stuck on the upper part turning to a gate electrode layer, and a poly silicon film 13 is anisotropically etched by using the resist layer 14 as a mask, thereby forming a gate electrode layer 15. As the result, residue 16 of poly silicon is formed at a step-difference part of an insulating film 12. Then the residue 16 is eliminated by performing isotropic etching without eliminating the resist layer 14. The isotropic etching is performed under the condition that RF power is 60-120W, by using mixed gas of SF6, He, CCl4, CF4 plasma as etching gas. Hence etching equivalent to the vertical direction can be performed also in the horizontal direction, so that the residue 16 can be quickly eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for manufacturing a semiconductor device, and particularly to an improvement in a method for forming electrodes and wiring.

(b) Prior Art In recent years, as semiconductor integrated circuits have become more highly integrated, the dimensions of electrodes and wiring have also become smaller.

Generally, anisotropic etching is used as a method for processing such electrodes and wiring with accurate and minute dimensions without causing short circuits or the like.

A conventional method for manufacturing a semiconductor device is shown in FIGS. 2A and 2B.

First, as shown in FIG. 2A, Si is placed on a silicon substrate (1).
An insulating film (2) made of n.

Here, the insulating film (2) has a steep step shape,
Such a shape is generally formed at the edge of a field oxide film.

Subsequently, a polysilicon film (3) is deposited by the LPCVD method.

Next, as shown in FIG. 2B, a resist layer (4) is coated above the portion that will become the gate electrode layer, and then, as shown in FIG.
) is subjected to an anisotropic etching process using an etching gas such as SF or plasma to form a gate electrode N(5).

According to this anisotropic etching process, since the etching gas acts only in the vertical direction on the polysilicon film (3), the amount of side etching can be extremely small, and the fine gate electrode layer (5) can be formed with high precision. It can be processed well.

However, since the vertical film thickness of the polysilicon film (3) on the stepped portion of the insulating film (2) is thicker than the film thickness of the gate electrode layer (5), as a result of anisotropic etching, There is a problem in that a polysilicon residue (6) is formed in this portion, causing a short circuit between the electrode layers through this residue (6).

Also, before anisotropic etching, a polysilicon film (3
) If foreign matter (oxide film or particles) having a masking effect is attached to the surface of the substrate, there is a problem that columnar residues are formed under the foreign matter due to anisotropic etching.

In this regard, the conventional technique has been to increase the amount of overetching in order to remove these residues.

(c) Problems to be Solved by the Invention However, it is difficult to completely remove the residue using this method.

Moreover, as shown in the first diagram, when the overetching amount of the anisotropic etching process is increased, the insulating film (2) is also etched at the same time, so that the thin part of the insulating film (2) is completely removed and the silicon substrate (1) is etched. There is a problem in that it causes damage such as crystal defects.

The present invention was created in view of the above problems,
The object of the present invention is to provide a method for forming electrodes and wiring in which residues generated during anisotropic etching can be removed without causing damage.

(d) Means for Solving the Problems The present invention comprises a step of depositing a conductive film on a semiconductor substrate via an insulating film, and selectively anisotropically etching the conductive film in a predetermined region. The method is characterized by comprising a step of forming an electrode layer, and a step of performing isotropic etching to remove residues of the conductive film remaining in areas other than the predetermined regions.

(*) Function According to the present invention, by applying isotropic etching to the residue of the conductive film produced by anisotropic etching, the residue can be quickly and completely removed mainly by using the horizontal component of isotropic etching. can be removed.

Moreover, in isotropic etching, the etching selectivity of the polysilicon film to the insulating film can be made larger than in anisotropic etching, so the amount of etching of the insulating film is small, and there is no risk of damaging the substrate. .

As a result, electrodes and wiring with minute dimensions can be formed with high precision without causing short circuits.

(F) Embodiment Next, an embodiment of the present invention will be described in detail with reference to FIGS. 1A to 1D.

First, as shown in Figure 1A, a silicon substrate (11) is
An insulating film (12) made of in.

Subsequently, a polysilicon film (13) is deposited to a thickness of 4000 nm using the LPCVD method.

Here, a refractory metal silicide film may be formed on the polysilicon film (13).

Next, as shown in FIG. 2B, a resist layer (14) is deposited above the portion that will become the gate electrode layer, and then as shown in FIG. 2C, using the resist layer (14) as a mask, a polysilicon film (13) is deposited. ) is subjected to an anisotropic etching process to form a gate electrode layer (15).

Here, the anisotropic etching is performed using SF and plasma as etching gas under the condition of RF puff -150 to 200W.

As a result, polysilicon residues (16) are formed in the stepped portions of the insulating films (1, 2).

Subsequently, isotropic etching is performed to remove the residue (16) without removing the resist layer (14).

Here, in isotropic etching, the etching gas is SF,
He, CCj! , , using a mixed gas of CF and plasma,
By performing the etching under the condition of RF power of 60 to 120 W, it is possible to perform etching in the horizontal direction equivalent to that in the vertical direction, so that the residue (16) can be promptly removed.

Further, columnar residues caused by foreign substances (oxide films or particles) having a masking effect can also be removed at the same time.

Furthermore, in the isotropic etching described above, S of polysilicon is
The etching selectivity ratio for the insulating film (12) can be set to 30:2, which is about twice that of anisotropic etching. There is also the advantage that there is no risk of damaging (11).

As described above, according to the embodiment of the present invention, the polysilicon residue generated by anisotropic etching can be quickly removed without damaging one substrate (11) by using isotropic etching. It is possible to form a fine gate electrode layer (15) with high precision without causing any damage.

(G) As described in detail, the present invention includes an isotropic etching process for removing conductive film residues caused by anisotropic etching, so that electrodes with minute dimensions can be removed. - Wiring can be formed with high precision without causing short circuits.

[Brief explanation of drawings]

1A to 1D are cross-sectional views showing a method for manufacturing a semiconductor device according to an embodiment of the present invention, and FIGS. 2A to 2D are cross-sectional views showing a method for manufacturing a semiconductor device according to a conventional example. .

Claims (2)

[Claims] (1) a step of depositing a conductive film on a semiconductor substrate via an insulating film; a step of selectively anisotropically etching the conductive film to form an electrode layer in a predetermined region; A method for manufacturing a semiconductor device, comprising the step of performing isotropic etching to remove residues of the conductive film remaining in areas other than the regions. (2) The method for manufacturing a semiconductor device according to claim 1, wherein the electrode layer is a gate electrode layer.