JP3143949B2 - Dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method used in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art In recent years, ULSI (ultra large)
e scale integration) In conjunction to the speed of the device, for example, tungsten polycide made of a laminated film of a doped polycrystalline silicon (DOPOS) from its upper tungsten silicide as the gate structures of transistors _{(WSi X) (W-polycide} ) Is being adopted.

[0003] Such a method of etching tungsten polycide is disclosed in the spring of 1990;
The method described in ZF-3 is known. This method is etching by a gas system without using chlorofluorocarbon,
Using an RF bias application type ECR plasma etcher,
Etching is performed using sulfur hexafluoride (SF ₆ ) and hydrogen bromide (HBr), and sidewalls are protected by deposits ( compound for forming a protective film; SiBr ₄ ) resulting from the addition of HBr. This allows anisotropic processing.

In addition, tungsten silicide (WSi
Two-stage etching is known in which _X ) is etched using SF ₆ + HBr, and then doped polysilicon (DOPOS) is etched with HBr.

Conventional techniques described above, for example, as shown in FIG. 4, on the SiO ₂ film 2 formed on the surface of the silicon substrate 1, successively doped polysilicon (DOPOS) film 3, a tungsten silicide (WSi _X) film A resist 5 having a desired pattern is patterned on a tungsten polycide structure formed by laminating the resist 4 and using this resist as a mask,
Successively WSi _X film 4, DOPOS film 3 SF ₆ + HBr, H
It is intended to perform etching using Br.

[0006]

However, when etching is carried out using such a conventional method, the sidewalls are not covered by SiBr ₄ deposited due to the addition of HBr until the just-etched state shown in FIG. Despite the protection effect, the supply of Si for forming SiBr ₄ is lost during over-etching performed to surely remove the DOPOS film 3 (this is because the DOPOS film disappears, and SiBr ₄ is removed from the underlying SiO ₂ film). Is not supplied), which causes a problem that the DOPOS film 3 is undercut as shown in FIG.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and it is an object of the present invention to provide a dry etching method which does not cause undercut when overetching a polycide film and a silicon-based thin film. Is what you do.

[0008]

Means for Solving the Problems] The present invention is, Siri
The reaction product between the dry etching and the thin film
While depositing as a protective film, the silicon-based thin film is etched.
In the dry etching method of a silicon-based thin film having a just etching step of quenching, the Jasutoe
After the etching step, SiB is applied to the etching gas.
Mixing by separately adding r ₄ as a compound for forming a protective film
The gas causes Si on the pattern side wall of the silicon-based thin film.
While depositing Br ₄ , the silicon-based thin film is etched.
Having an over-etching step of
To solve the problem.

Further, a silicon-based thin film and an etching gas
Deposits the reaction product of
Stacked film of point metal silicide thin film and the silicon-based thin film
Having a just etching process for etching
In the dry etching method of Con-based thin film, the Ja
After the strike etching step, the etching gas
SiBr ₄ was separately added as a protective film forming compound.
Pattern side wall of the silicon-based thin film
With depositing SiBr _4, the said silicon-based film
Having an over-etching step for etching
And it has a second aspect.

[0010]

According to a first aspect of the present invention, when a silicon-based thin film is over-etched, a gas containing SiBr ₄ is supplied to the silicon-based thin film to form a SiBr ₄ (sidewall) on the sidewall of the silicon-based thin film.
(A compound for forming a protective film) is adhered to prevent undercut.

According to the second aspect of the present invention, similarly to the first aspect of the present invention, the side wall of the silicon-based thin film which is the lower layer of the refractory metal silicide thin film is also formed with SiBr ₄ (for forming a side wall protective film) during over-etching . is a protective film made of a compound) is formed, it is possible to anisotropic processing.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the dry etching method according to the present invention will be described below with reference to the embodiments shown in FIGS.

First, as shown in FIG.
A doped polysilicon (DOPOS) film 12 as a silicon-based thin film is formed on a SiO ₂ film 11 formed on
After depositing the VD method, a tungsten polycide structure by laminating a tungsten silicide (WSi _X) film 13 thereon. Then, a resist is patterned on the tungsten silicide film 13.

Next, the tungsten silicide film 13 is etched under the following etching conditions (just etching).
Process) .

Etching gas and its flow rate Sulfur hexafluoride (SF ₆ ): 15 _SCCM Hydrogen bromide (HBr): 35 _SCCM Pressure: 5 mTorr Microwave current: 250 mA RF bias: 150 W Next, the doped polysilicon film 12 is removed. Etching is performed under the following etching conditions (just etching step) .

Etching gas and its flow rate Hydrogen bromide (HBr) 50 _SCCM Pressure 5 mTorr Microwave current 250 mA RF bias 200 W When etching the doped polysilicon film 12, the etching gas is caused by the addition of HBr. And SiB
sidewall protective film 12a made of r _X are formed.

After that, from the state where the underlying SiO ₂ film 11 has begun to be exposed, over-etching (over-etching step) is performed under the following etching conditions.

Etching gas and its flow rate Hydrogen bromide (HBr) 40 _SCCM SiBr ₄ 10 _SCCM Pressure 5 mTorr Microwave current 250 mA RF bias 200 W As described above, SiBr ₄ is added to the etching gas during over-etching. As a result, SiBr ₄ adheres (deposits) to the sidewalls of the doped polysilicon film 12, thereby preventing the occurrence of undercut. If etching is performed only with HBr without adding SiBr ₄ , the SiBr ₄ forming the side wall protective film 12a is separated from the side wall, and an undercut occurs. Further, since Si in the underlying SiO ₂ film 11 is strongly bonded to oxygen, it does not form SiBr ₄ with Br in HBr.

The invention has been described by applying the present invention to a tungsten polycide structure is a laminated film of a silicon-based thin film and the refractory metal silicide film, Ja silicon-based thin film
The present invention can be widely applied to the case where the strike etching and the over etching are performed.

In the above embodiment, the etching is performed in three stages, namely, the just etching of the tungsten silicide film 13, the just etching and the over etching of the doped polysilicon film 12. Only SiBr ₄
May be added.

Further, in order to promote the formation of the sidewall protective film, oxygen (O ₂ ) and nitrogen (N ₂ ) are used during over-etching.
Alternatively, SiO _x , SiN or the like may be formed on the side wall by adding such a material.

[0022]

As is apparent from the above description, according to the dry etching method of the present invention, it is possible to prevent the silicon-based thin film from being undercut during over-etching, and to perform good anisotropic processing. effective.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a process of an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the steps of the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing the steps of the embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a process of a conventional example.

FIG. 5 is a cross-sectional view showing a process of a conventional example.

FIG. 6 is a cross-sectional view showing a process of a conventional example.

[Explanation of symbols]

11: SiO ₂ film, 12: doped polysilicon film, 1
2a: sidewall protective film, 13: tungsten silicide film.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification code FI H01L 29/78 301G (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/3065 H01L 21/302 H01L 21 / 28 H01L 29/43 H01L 29/78

Claims (2)

(57) [Claims] 1. The method of claim 1, wherein the silicon thin film and the dry etching
The reaction product is deposited as a sidewall protective film, and
Just etching process to etch recon-based thin film
In the method of dry-etching a silicon-based thin film having the method, after the just etching step, the etching gas
Separately added SiBr ₄ as a protective film forming compound
The silicon-based thin film is patterned by the added mixed gas.
SiBr ₄ is deposited on the side wall of
Has an over-etching process for etching system thin films
The dry etching method according to claim Rukoto. 2. The reaction between a silicon-based thin film and an etching gas.
The reaction product is deposited as a sidewall protective film,
A laminated film of a metal silicide thin film and the silicon-based thin film is etched.
Silicon with just etching step
In the dry etching method for a system thin film , after the just etching step, the etching gas
Separately added SiBr ₄ as a protective film forming compound
The silicon-based thin film is patterned by the added mixed gas.
SiBr ₄ is deposited on the side wall of
Has an over-etching process for etching system thin films
The dry etching method according to claim Rukoto.