JPH05136103A - Etching method - Google Patents

Abstract

PURPOSE:To prevent the occurrence of side etching due to the insufficiency of a side wall protective film caused by a high aspect ratio at the time of Al dry etching. CONSTITUTION:At the time of performing dry etching using a gas containing chlorine, W 5 having an extremely high selection ratio against Al 4 is used as an etching mask so that the film thickness of the mask can be reduced. Since the aspect ratio of a pattern can be lowered and the working-side wall of a fine pattern can be protected when the film thickness of the etching mask is reduced, the occurrence of side etching can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for etching fine Al wiring.

[0002]

2. Description of the Related Art In dry etching of Al, chlorine-based gas is generally used. Since Al and Cl have extremely high reactivity, unless the processed side wall is protected by a reaction product or the like, side etching occurs and a good pattern cannot be formed. Along with the high integration, the pattern space becomes narrower, and at the same time, the aspect ratio of the pattern becomes higher due to the use of a thick resist such as a multilayer resist. Therefore, as shown in FIG. 5, the sidewall protection film is not sufficiently formed at the bottom of the high aspect ratio pattern, and side etching occurs.

To suppress the occurrence of side etching, Al
It is necessary to form a protective film on the entire processed side wall.
If an attempt is made to form a protective film up to the bottom of the high aspect ratio pattern, an excessive film is formed on the low aspect ratio pattern, which cannot be completely removed after etching, causing defects. Although the aspect ratio can be lowered by reducing the thickness of the resist mask, generally, in the reactive ion etching method of Al, the etching rate ratio (selection ratio) between Al and the resist is as low as 1 to 3, and it is necessary to reduce the thickness. There is a limit. In addition, a method of preventing defects caused by a protective film residue by using SiO ₂ or the like as an etching mask is disclosed in
It is disclosed in Japanese Patent Publication No.-23944.

[0004]

The problem of the above-mentioned conventional technique is that the selectivity of Al to the resist or SiO ₂ which is an etching mask is low. In order to improve the processing accuracy of Al etching, the conditions under which the energy of reactive ions is high are often used, and due to the high step difference of the underlying layer, the substantial Al film thickness is increasing. Therefore, a thick SiO ₂ mask is required, and the problem of side etching associated with a high aspect ratio cannot be solved. Further, when forming the multi-layered Al wiring, the insulating film on this Al causes the through holes thereabove to become deeper. Therefore, it is necessary to use, as the mask material, a material that is conductive and that can obtain a high selection ratio.

An object of the present invention is to form a fine Al wiring pattern with high dimensional accuracy.

[0006]

The above object is achieved by using W, which has an extremely high etching rate ratio (selectivity ratio) with respect to Al, as an etching mask in dry etching of Al using chlorine gas. It The film thickness of W may be 1/10 or less of that of Al, and it is not necessary to remove W after etching Al.

[0007]

Function: By setting the etching mask to W, Al
Since the aspect ratio at the time of etching can be lowered and the processed side wall of the fine space portion can be protected, Al wiring can be formed with high dimensional accuracy without side etching.

[0008]

The present invention will be described in detail below with reference to examples.

<Embodiment 1> FIGS. 1 and 2 show an embodiment of the present invention. The thickness of the Si substrate 1 is reduced to 0.1 by the atmospheric pressure CVD method.
Deposit 3 μm phosphorous glass (PSG) 2. Next, a Ti target, argon N ₂ atmosphere (A
r) TiN having a thickness of 0.1 μm formed by a sputtering method using a gas
After depositing and depositing No. 3, an Al film 4 containing 1% Si having a thickness of 0.9 μm is deposited by a sputtering method using an argon gas. Further, 100 parts of hydrogen (H ₂ ), argon (Ar) and tungsten hexafluoride (WF ₆ ) are formed on Al 4.
After a W film 5 having a thickness of 0.1 μm is deposited and deposited at a ratio of 5: 2 by a low pressure CVD method, a resist pattern 6 is formed by a photolithography method (FIG. 1A).

The substrate 1 is etched by a parallel plate reactive ion etching apparatus with a flow rate of sulfur hexafluoride (SF ₆ ) of 50 sccm and a high frequency power of 0.2 W / cm ² under a pressure of 0.2 Torr. Then, a shape drawing 1 (b) is obtained. FIG. 3 shows the high frequency power dependence of the etching rates of the resist and W. At this 0.2 W / cm ² , the resist etching rate is
It becomes 1/5 of W. The processing accuracy of W is about 0.05 μm when etched at room temperature.
When cooled in the range from ℃ to -50 ℃, there was no side etching, and etching could be performed almost according to the mask dimensions. Also,
Al4, which is the base, is hardly etched because Al fluoride is formed on the surface. The resist is removed by O ₂ plasma to obtain the shape shown in FIG.

Next, boron trichloride (BCl ₃ ) and chlorine (C
L ₂ ) and carbon tetrachloride (CCl ₄ ) gas flow rates of 80 sccm, 20 sccm and 35 sccm, respectively, and pressure of 0.2 Torr.
Underneath, applying a high frequency power of 1.3 W / cm ² to Al4
Is etched into the shape shown in FIG. W and A
The dependence of the etching rate of l on the high frequency power is shown in FIG. Even if the high frequency power is increased, the etching rate of W is 1/100 or less of that of Al. This is because the vapor pressure of WCl _x , which is a reaction product of W and Cl, is low.
_This is because both ₅ and WCl ₆ have a vapor pressure of about 10 ⁻⁶ Torr at room temperature and the dry etching reaction does not proceed. From this result, the film thickness of W that serves as an etching mask is at least Al.
1/100 of the film thickness of

Finally, the flow rates of boron trichloride (BCl ₃ ) and carbon tetrachloride (CCl ₄ ) are set to 80 sccm and 35 sccc, respectively.
When the TiN film is etched by applying a high frequency power of 0.2 W / cm ² under m and a pressure of 0.2 Torr, the TiN film is etched as shown in FIG.
In addition, O ₂ plasma and sulfamic acid (HS
When the side wall protective film is removed with an O ₃ NH ₂ ) solution, the result is shown in FIG.

[0013] The etching of W, in addition to CF ₄ of SF _6,
A gas containing other F such as NF ₃ may be used. Also, O in Cl _2
Even with a mixed gas containing ₂ to 10% to 50%, WO
It was possible because it became Cl ₄ and reacted. When the content of O ₂ was 10% or more, the underlying Al was not etched because an oxide was formed on the surface. In etching Al and TiN, CCl ₄ was used as a carbon source to protect the sidewalls.
Were mixed, but this may be CHCl ₃ , CH ₃ Cl, or the like. Further, when the substrate temperature was lowered to about 0 ° C., the etching of Al with Cl was suppressed, and good anisotropic etching was achieved only with Cl ₂ and BCl ₃ .

According to this embodiment, by using W having a high selection ratio with respect to Al as the etching mask, the mask can be thinned, and therefore side etching due to the high aspect ratio can be prevented. The material to be processed is A in addition to Al.
It may be a 1-Si alloy, an Al-Cu alloy, or a laminated film of Al and a metal other than W such as Ti and TiN. Although parallel plate type reactive sputter etching is used here, similar results can be obtained by using an apparatus such as microwave plasma etching or magnetron plasma etching. The W of the mask may be etched by an F-based gas that does not etch the underlying Al or a Cl-based gas to which O ₂ is added, and the Al-based film may be etched by a Cl-based gas that is difficult to etch W. Further, as the mask material, in addition to W, Mo that can obtain a high selection ratio with respect to Al
And so on.

[0015]

According to the present invention, in Al dry etching, side etching due to a high aspect ratio can be prevented, and Al wiring can be processed with high dimensional accuracy.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing a process of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of the high frequency power dependence of the etching rate of W.

FIG. 4 is an explanatory diagram of high frequency power dependence of etching rates of Al and W.

FIG. 5 is a sectional view showing a conventional technique.

[Explanation of symbols]

1 ... Si substrate, 2 ... PSG, 3 ... TiN, 4 ... Al, 5
... W, 6 ... Resist, 7 ... Side wall protective film, 8 ... Side etch.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadao Morimoto 5-20-1 Kamimizumoto-cho, Kodaira-shi, Tokyo Hiritsu Cho-LS Engineering Co., Ltd. (72) Inventor Hisashi Hisashi Man 1-280, Higashikoigokubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (2)

[Claims] 1. A method using chlorine or a gas containing chlorine
1. An etching method, wherein W or Mo is used as an etching mask in a method of dry-etching a single-layer film of Al, Al-Si alloy, Al-Cu, or a laminated film of these and a metal such as Ti or TiN. 2. An etching method in which W of claim 1 is processed by a low temperature dry etching method using a mixed gas of chlorine and oxygen or a gas containing fluorine.