JP3077224B2 - 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, and more particularly to an etching method for an aluminum-based material.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of ULSI, wiring rules have become finer and processing accuracy has become increasingly severe.

In particular, in the case of aluminum wiring, since the anisotropy is achieved by protecting the side walls with the decomposition product of the resist, the ion incident energy cannot be reduced to a certain extent, and the selectivity with respect to resist and base is not so large. Therefore, in order to improve the selectivity with respect to the resist and the base, it is necessary to reduce the incident energy of ions and reduce the amount of sputtering of the resist or increase the amount of chlorine radicals generated and increase the etching rate of aluminum. , Is said to be effective.

[0004]

However, when the amount of resist sputter is reduced or the amount of chlorine radicals generated is increased in order to increase the etching rate of aluminum, it is necessary to protect the aluminum sidewalls. There is a problem in that the amount of resist spatter is small, the shape usually deteriorates, and an undercut occurs.

[0005] Therefore, a certain amount of incident energy of ions is required. Therefore, sputtering of the resist and the base cannot be prevented by ion sputtering, and the selectivity cannot be increased after all. For example, CCD
In a (solid-state imaging device) or the like, the underlying step is very large (1.5 to 2.0 μm), and overetching requires a considerable amount (100 to 200%) as compared with other devices. At this time, if the selectivity with respect to the base is not large, there has been a problem that the base insulating film is etched.

An object of the present invention is to provide a dry etching method which enables anisotropic processing of an aluminum-based material in a low ion energy region and which can increase the selectivity between a resist and a base.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method of dry etching an aluminum-based material, wherein the etching is performed using a gas obtained by adding hydrogen sulfide to a chlorine-based gas.

[0008]

The ion (S) in the hydrogen sulfide (H ₂ S) has a depositing function at a low temperature by being added to the etching gas, and deposits on the side wall of the aluminum-based film to provide a side wall protecting function. The hydrogen in hydrogen sulfide (H ₂ S)
It reacts with the resist decomposed substance and adheres to the side wall to exert a side wall protecting effect in addition to the action of the ions (S). Further, chlorine (Cl) in a chlorine-based gas also exerts a sidewall protecting effect by being excessively added to the etching gas. Thus, chlorine-based gas, hydrogen (H) and ion (S)
By adding hydrogen sulfide (H ₂ S) containing, the resist decomposition product effectively contributes to side wall protection, and the side wall protection of sulfur (S) can be used, so that anisotropic processing can be performed in a low ion energy region. It becomes possible.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the dry etching method according to the present invention will be described below based on embodiments shown in the drawings.

[0010] In this embodiment, first, an insulating film 2 made of SiO ₂ on the silicon substrate 1, the insulating film 2
A titanium (Ti) film 3 and a titanium oxynitride (TiON) film 4 are sequentially formed as barrier metal layers thereon,
Further, an aluminum (Al-Si) wiring 5 is formed on the titanium oxynitride film 4 (FIG. 1).

Next, a resist 6 is applied on the aluminum wiring 5 and formed into a desired pattern by lithography.

Then, dry etching is performed using the resist 6 as a mask. In this embodiment, the dry etching is performed using an RF bias application type ECR etching apparatus. The etching conditions are shown below.

○ Wafer temperature during etching: -20 ° C. Etching gas and its flow rate Boron trichloride (BCl ₃ ): 20 _SCCM Chlorine (Cl ₂ ): 50 _SCCM Hydrogen (H ₂ S): 50 _SCCM ○ Atmosphere Pressure: 10 mTorr O μ-wave output: 300 mA O RF bias: 20 W When etching is performed under such conditions, as shown in FIG.
Anisotropic processing is achieved. At this time, the aluminum film 5
Etc. on the side wall of the film to be etched as shown in FIG.
The sidewall protection film 7 is formed.

The side wall protective film 7 is made of hydrogen sulfide (H ₂ S)
It is formed by depositing a substance in which hydrogen (H) contained therein has reacted with a resist decomposition product and sulfur (S) in hydrogen sulfide (H ₂ S). As described above, even when etching is performed in the low ion energy region, the side wall protective film 7 is easily formed and has a side wall protective effect, so that anisotropic processing can be performed.

Therefore, in this embodiment, it is possible to lower the ion energy as compared with the prior art, and it is possible to increase the selection ratio between the resist and the base.

The sulfur (S) thus adhered to the side wall can be easily removed by, for example, performing oxygen (O ₂ ) ashing.

Although the embodiment has been described above, the present invention is not limited to this, and various design changes accompanying the gist of the configuration are possible.

For example, in the above embodiment, boron trichloride (BCl ₃ ) and chlorine (Cl ₂ ) were used as the chlorine-based gas. However, other chlorine-based gas may be used. Or a single gas may be used. In particular, these chlorine-based gases are preferably added to the etching gas at a rate of about 10 to 50%.

In the above embodiment, Al-Si was used as the aluminum-based material, but Al, Al-C
Of course, u may be applied.

Further, in the above embodiment, the wafer temperature at the time of etching was set to -20 ° C., but it is possible to deposit sulfur (S) by cooling to a temperature below room temperature.

[0021]

As is apparent from the above description, according to the dry etching method of the present invention, anisotropic processing of an aluminum-based material in a low ion energy region becomes possible, and a resist and a base can be used. This has the effect of increasing the selectivity of.

[Brief description of the drawings]

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

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

[Description of Signs] 5 ... aluminum film, 6 ... resist, 7 ... sidewall protective film.

Claims (1)

(57) [Claims] 1. A dry etching method for an aluminum-based material, wherein etching is performed using a gas obtained by adding hydrogen sulfide to a chlorine-based gas.