JPH061770B2 - Dry etching method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a dry etching method, and particularly to a dry etching method suitable for etching aluminum and an alloy containing aluminum as a main component (hereinafter, abbreviated as an aluminum alloy). It is about the method.

[Background of the Invention]

In the dry etching process of a wafer, which is one step of manufacturing semiconductor devices, it is necessary to have both high speed and precision of etching. High speed and precision are important factors because the high speed affects the productivity of semiconductor devices and the precision controls the fineness for high integration.

In order to achieve both high speed and precision of etching at the same time, use an etching device suitable for the material to be etched,
And it must rely on a suitable etching method. As the etching apparatus, there is used an apparatus of a type in which high-frequency electric power is applied to one of a pair of parallel disk-shaped electrodes facing each other and a wafer is etched by plasma generated by glow discharge generated between the electrodes. This type of apparatus includes an apparatus of a type that simultaneously etches a plurality of wafers set on electrodes, and an apparatus of a type that sets one wafer on an electrode to perform etching, each having its own characteristics.

On the other hand, in the etching method in the case where the material to be etched is aluminum or an aluminum alloy containing aluminum as a main component, a chlorine-based gas is used as the gas introduced into the reaction chamber.

Recently, a gas mixture of silicon tetrachloride (SiCl ₄ ), boron trichloride (BCl ₃ ), chlorine (Cl ₂ ) and helium (He) has been proposed as an etching method that combines high speed and precision. Single WaferPlasma Etching; Solid State
Technology / April 1982).

According to this, the gas flow rate of SiCl ₄ is 190 to
300 SCCM, BCl ₃ is 100 to 190 SCCM, Cl ₂
Is 100-190SCCM, He is 800-2000SC
In CM, the total flow rate is 1190 to 2680 SCCM, which is a large flow rate that is several times the gas flow rate in normal dry etching. Furthermore, the discharge power density
2.2 to 3.0 W / cm ^3, which is much higher than usual.

Since the reaction chamber must be maintained at a certain depressurized state, when the gas flow rate becomes large, the capacity of the exhaust pump must be increased or a special pump having a high displacement must be adopted.
Furthermore, when the discharge power density becomes large, a high-frequency oscillating equipment with large capacity is required. This is a direct factor in that the dry etching apparatus including the auxiliary equipment becomes large and expensive.

[Object of the Invention]

An object of the present invention is to achieve a high speed and precision of etching of aluminum and aluminum alloys with a small discharge power density without increasing the flow rate of an etching gas, so that the dry etching apparatus can be made small and inexpensive. It is to provide a dry etching method.

[Outline of Invention]

The present invention uses a gas in which silicon tetrachloride (SiCl ₄ ), chlorine (Cl ₂ ) and carbon tetrachloride CCCl ₄ ) are mixed at a ratio of 40:40:10 as an etching gas, and the etching gas is used at an absolute pressure. The invention is characterized in that plasma is generated under a reduced pressure of 40 Pa to etch aluminum or an aluminum alloy, and the aluminum and aluminum alloy can be etched at high speed with a small discharge power density without increasing the flow rate of the etching gas. It seeks to achieve precision.

Example of Invention

In the etching method of aluminum and aluminum alloys, we have conducted intensive experiments to obtain high speed and precision, and a small flow rate due to a mixed gas of SiCl ₄ + Cl ₂ and
It was found that a high speed can be achieved in precision with a low discharge power density, and precision can be achieved while maintaining high speed with a mixed gas of SiCl ₄ + Cl ₂ + carbon tetrahalide.

That is, 13.56 MHz high frequency power was applied to the lower electrodes of the pair of electrodes, one wafer patterned with photoresist was placed on the lower electrodes, and etching was performed by changing the high frequency power. The drawing shows the relationship between the etching rate and the discharge power density under the two conditions.

The experimental condition is that the electrode spacing is 30 mm and the absolute pressure is 40 Pa in both conditions A and B. Regarding gas flow rate, condition A is SiCl ₄
40SCCM, Cl ₂ 40SCCM, total flow 80SCC
M, condition B is SiCl ₄ 40SCCM, Cl ₂ 40SCC
M, CCl ₄ as carbon tetrahalide 10 SCCM, total flow 90 SCCM.

As shown in the drawing, small discharge power density 0.5 to 1.0 W / cm ³
The etching rate was 1,000 to 2,000 nm / min, and high-speed etching was obtained.

On the other hand, the precision of etching is usually judged by the reduction of the pattern width before and after etching, that is, the difference ΔW between the photoresist size before etching and the pattern width after removing the photoresist after etching. When the resist dimension before etching was 2 μm, ΔW under the condition A was as large as 0.4 to 1.2 μm, which was far from the precision etching.
When condition B is the same 2 μm, ΔW is 0.1 μm,
The cross-sectional shape of the etching was vertical, and precision etching faithful to the photoresist pattern was realized.

Note that He has an extremely large thermal conductivity as compared with other gases, and is effective in cooling the wafer, and is often used. Also in the present invention, He is 5 to 30 SC in the conditions A and B.
An experiment was carried out when CM was added, but the etching rate and precision were not adversely affected. Therefore, the present invention naturally includes the case where He is used as the gas species of the fourth component.

In the above description, CCl ₄ was used as the carbon tetrahalide, but at least chlorine was used as the halogen.
In the form of containing more than one, a substitution compound of chlorine and fluorine of CCl ₄ , that is, CFCl ₃ , CF ₂ Cl ₂ and CF ₃ Cl are effective for achieving etching precision.

In the dry etching method as in the present embodiment, it is possible to achieve high speed and precision in etching aluminum and aluminum alloys with a low discharge power density and a small amount of etching gas flow rate which have never been achieved. The capacity of the high-frequency oscillating equipment becomes small and the exhaust pump also becomes small, so that the dry etching apparatus including these incidental equipment can be made small and inexpensive.

〔The invention's effect〕

As described above, the present invention uses, as an etching gas, a gas obtained by mixing silicon tetrachloride (SiCl ₄ ), chlorine (Cl ₂ ), and carbon tetrachloride CCl ₄ ) in a ratio of 40:40:10. The etching gas is turned into plasma under a reduced pressure of 40 Pa to etch aluminum or an aluminum alloy, thereby increasing the etching speed of aluminum and an aluminum alloy without increasing the flow rate of the etching gas and with a small discharge power density. The precision can be achieved, and there is an effect that the dry etching apparatus can be made small and inexpensive.

[Brief description of drawings]

The drawing is a diagram of discharge power density and etching relationship obtained by the present inventors.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshimasa Fukushima 502 Jinritsucho, Tsuchiura-shi, Ibaraki Machinery Research Institute, Hiritsu Manufacturing Co., Ltd. (56) Reference JP-A-57-123978 (JP, A)

Claims (1)

[Claims] 1. A gas in which silicon tetrachloride (SiCl ₄ ), chlorine (Cl ₂ ) and carbon tetrachloride (CCl ₄ ) are mixed at a ratio of 40:40:10 is used as an etching gas. A dry etching method, which comprises forming plasma under a reduced pressure of 40 Pa absolute and etching aluminum or an alloy containing aluminum as a main component.