JPH05234958A - Precise working method for semiconductor material containing group vi element - Google Patents

Abstract

PURPOSE:To obtain a reactive gas which has a slow etching speed, causes less damages to substrates, and is excellent in working shape, especially, in verticality by using a mixed gas containing an ethane gas and hydrogen gas as the etching gas. CONSTITUTION:At the time of etching a semiconductor material containing group VI element by using a reactive gas, a mixed gas containing an ethane gas and hydrogen gas is used as the reactive gas. For example, an etching mask 2 is formed on a ZnSe crystal 1 by using a photoengraving technique. Then, after putting the crystal 1 in the vacuum tank 3 of a reactive ion etching system and evacuating the tank 3, the ethane gas and hydrogen gas are respectively introduced into the tank 3 through introducing ports 4 and 5 as the reactive gas. When plasma is generated by applying a high-frequency voltage across facing electrodes 7, etching takes place in the window areas of the mask 2 where the mask 2 does not exists due to the reaction between the semiconductor material and plasma ions. It is necessary to set the mixing ratio of the ethane gas in the mixed gas to <=15vol.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine processing method for a semiconductor material containing a Group 6 element using a dry etching method.

[0002]

2. Description of the Related Art Conventionally, one of semiconductor materials containing a Group 6 element has been used.
As a method of etching a 2-6 group compound semiconductor material, which is one of the two, there is a method shown in Electron Letter (Electron. Lett.) Vol. 27 (1), 73-75 (1991), which is a reactive ion etching ( The Reactive Ion Etching) method uses a mixed gas of methane (CH ₄ ) and hydrogen (H ₂ ) and has a structure as shown in FIG. In the figure, (9) is a ZnTe crystal, (2) is an etching mask, and (3)
Is a vacuum chamber of a reactive ion etching apparatus, (8) is a methane gas introduction port, (5) is a hydrogen gas introduction port, (6) is an exhaust port, and (7) is a high frequency counter electrode.

First, a ZnTe crystal (9) to be processed is put into a vacuum chamber (3) and evacuated, and then methane gas (CH ₄ ) and hydrogen gas (H ₂ ) are respectively supplied as reactive gases in the vacuum chamber. Install from the installation ports (8) and (5). Crystals to be etched on one side of the counter electrode (7) for generating plasma
(9) is placed, a high frequency is applied between the counter electrodes (7), the mixed gas is ionized, and the ZnTe crystal (9) is etched by the reaction with the material to be etched. In order to cover the portion of the crystal (9) that does not require etching, an etching mask (2) is deposited on the crystal in advance, and an unnecessary portion of the etching mask (2) is formed by a method such as photolithography.
Is removed, a window is opened, and then etching is performed in the above plasma. The radio frequency (RF) power, mixed gas pressure, gas partial pressure ratio, etc. are adjusted to obtain a good surface condition and an appropriate etching rate. In the above literature, in ZnTe,
It is described that relatively good etching is possible at a total pressure of mixed gas of 3.3 Pa and a CH ₄ concentration of 11%. Further, it is said that the radio frequency (RF) power of plasma may be around 0.4 W per 1 cm 2.
The inclination angle of the side surface is about 85 degrees, and the etching rate is 120.
Values of nm / min have been obtained.

[0004]

A vertical and smooth etching surface is required when used for processing a resonator mirror of a semiconductor laser or a stripe structure of a waveguide, and etching with a mixed gas of methane and hydrogen is required. The etching rate was relatively high and was not always satisfactory.

The present invention has been made to solve the above problems, and by using a hydrocarbon gas having a larger molecular weight than methane, the etching rate is slow, the damage to the substrate is small, and the processing is performed. It is an object of the present invention to provide a fine processing method for a Group 6 element-containing semiconductor material which is excellent in shape, particularly verticality.

[0006]

The fine processing method for a Group 6 element-containing semiconductor material according to the present invention uses ethane (C ₂ H ₆ ) as an etching gas instead of methane (CH ₄ ).

That is, the method for finely processing a Group 6 element-containing semiconductor material according to the present invention is a method of etching a Group 6 element-containing semiconductor material using a reactive gas, wherein a mixture containing ethane gas and hydrogen gas as the reactive gas is used. It is characterized by using gas.

[0008]

The ethane gas (C ₂ H ₆ ) in the present invention reacts with the group 6 element of the group 6 element-containing semiconductor material to become a volatile organometallic gas, and the group 6 element is also a hydrogen gas (H ₂ ). It reacts and becomes a gas of a hydrogen compound, which is removed and the semiconductor material containing a Group 6 element is etched.

[0009]

Embodiment 1 FIG. 1 is a block diagram showing an embodiment of the present invention, in which (1) is Z
nSe crystal, (2) etching mask, (3) vacuum chamber of reactive ion etching apparatus, (4) ethane gas inlet port, (5) hydrogen gas inlet port, (6) exhaust port,
(7) is a high frequency counter electrode.

An etching example using ZnSe according to the method of the present invention will be described with reference to FIG. First, the etching mask (2) is applied to the ZnSe crystal (1) using the photoengraving technique.
To form. After that, the ZnSe crystal (1) with the etching mask (2) was subjected to reactive ion etching (Reactive
Ion Etching) After putting it in the vacuum chamber (3) of the device and exhausting it,
Ethane gas (C ₂ H ₆ ) and hydrogen gas (H ₂ ) as reactive gases
And are introduced from the introduction ports (4) and (5), respectively. As in the conventional example, a high frequency is applied between the counter electrodes (7) to generate plasma. In the window region where the etching mask (2) does not exist, etching occurs due to the reaction with the plasma ions. The group 6 element of the group 6 element-containing semiconductor material, which is the material to be etched, reacts with the ethane gas (C ₂ H ₆ ) to generate a volatile organometallic gas [eg, if it is Se of ZnSe crystal, (C ₂ H ₅ ) ₂ Se] is produced, and the Group 6 element also reacts with hydrogen gas to form a hydrogen compound gas (ZnSe
In the case of crystalline Se, H ₂ Se) is generated and etching is performed. At this time, elements other than Group 6 elements are ethane gas
By reacting with (C ₂ H ₆ ), a volatile organometallic gas [eg, (C ₂ H ₅ ) ₂ Zn] in the case of the Group 2 element Zn of the ZnSe crystal is generated and etching is performed. Therefore, unnecessary elements and compounds are not generated on the material to be etched, and a smooth etching surface without residue is obtained. After the etching treatment is completed, the etching mask (2) is taken out from the vacuum chamber (3) and completed. Etching conditions such as etching rate depend on the total pressure of the mixed gas, the composition ratio of the mixed gas, the radio frequency (RF) power, and the like. In the result of actual measurement, for example, Z
When etching the nSe crystal (1), an insulating film such as a silicon oxide film or a silicon nitride film is used as an etching mask, C ₂ H ₆ is 3%, the total pressure of the mixed gas is 14 Pa,
Radio frequency (RF) power of 0.6 per square centimeter
When W is set, the etching rate is 20 nm / min, which is smaller than the conventional method (120 nm / min), and etching with less damage is possible.

In the method of the present invention, the proportion of ethane gas in the mixed gas of ethane gas and hydrogen gas must be 15% by volume or less. This is because if the proportion of ethane gas exceeds 15% by volume, only carbon polymer formation and adhesion occur, not etching. Further, in the method of the present invention, the high frequency power during etching is set to 0.4 W or more per square centimeter. This is because etching does not occur when the high frequency power is less than 0.4 W per square centimeter. Further, in the method of the present invention, the total pressure of the mixed gas of ethane gas and hydrogen gas at the time of etching is about 15 Pa (about 115 mTorr).
r) Below This is because the etching surface becomes rough under a high gas pressure.

In the method of the present invention, a silicon oxide film or a silicon nitride film was used as a mask material at the time of etching in the above embodiment.
Ox), silicon nitride (SiNx) or photoresist can be used.

In the above description, the case where a zinc selenide (ZnSe) crystal is etched as a Group 6 element-containing semiconductor material has been described, but other Group 6 element-containing semiconductor materials such as cadmium selenide (CdSe) and zinc sulfide are described.
(ZnS), cadmium sulfide (CdS), zinc telluride (Z
nTe), cadmium telluride (CdTe) or mixed crystals thereof, or copper indium selenide (CuInS)
e ₂ ), copper gallium selenide (CuGaSe ₂ ), copper aluminum selenide (CeAlSe ₂ ), silver gallium selenide
(AgGaSe ₂ ), copper indium sulfide (CuInS ₂ ), copper gallium sulfide (CuGaS ₂ ), copper aluminum sulfide (Cu
The same effect as that of the above-described embodiment can be expected for AlS ₂ ), silver gallium sulfide (AgGaS ₂ ), or a mixed crystal thereof.

In the above description, the case where the reactive ion etching method is used as the dry etching method has been described. However, the reactive ion beam etching (Reactiv
eIon Beam Etching) method and ECR (Electron Cyclotron Re
The same effect is expected by using this C ₂ H ₆ and H ₂ mixed gas in other dry etching methods such as assist etching utilizing scanning of various beams and electric fields in addition to the plasma etching method. it can.

[0015]

Since the method of the present invention is configured to use a mixed gas of ethane gas and hydrogen gas as the reactive gas used in etching, it has the following effects: Group 6 In the etching of element-containing semiconductor materials, by using a mixed gas of ethane gas and hydrogen gas as a reaction gas instead of the mixed gas of methane gas and hydrogen gas of the conventional method, the etching rate is slow, the etching surface is good and the micromachining property is good. Excellent results are obtained.

[Brief description of drawings]

FIG. 1 is a schematic view showing reactive ion etching according to Example 1 of the present invention.

FIG. 2 is a schematic diagram showing conventional reactive ion etching.

[Explanation of symbols]

 1 ZnSe crystal 3 Vacuum tank 4 Ethane gas inlet port 5 Hydrogen gas inlet port

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayuki Imaizumi 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation Central Research Institute (72) Inventor Toshiro Isu 8-1-1 Tsukaguchihonmachi, Amagasaki Mitsubishi Central Research Institute of Electric Co., Ltd. (72) Inventor Yuji Abe 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation Central Research Institute (72) Toshiyuki Oishi 8-1-1 Tsukaguchihonmachi, Amagasaki Mitsubishi Electric Corporation Company Central Research Institute (72) Inventor Teruhito Matsui 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation

Claims (8)

[Claims] 1. A method for etching a group 6 element-containing semiconductor material using a reactive gas, wherein a mixed gas containing ethane gas and hydrogen gas is used as the reactive gas, and a fine group 6 element-containing semiconductor material is obtained. Processing method. 2. The fine processing method for a Group 6 element-containing semiconductor material according to claim 1, wherein etching using plasma is used as the etching method. 3. The fine processing method for a Group 6 element-containing semiconductor material according to claim 1, wherein the proportion of ethane gas in the mixed gas of ethane gas and hydrogen gas is 15% by volume or less. 4. The method for finely processing a Group 6 element-containing semiconductor material according to claim 2, wherein the high frequency power during etching is 0.4 W or more per 1 cm 2. 5. The method for microfabrication of a Group 6 element-containing semiconductor material according to claim 1, wherein the total pressure of the mixed gas of ethane gas and hydrogen gas at the time of etching is about 15 Pa or less. 6. The method according to claim 1, wherein silicon oxide (SiOx), silicon nitride (SiNx) or photoresist is used as a mask material during etching.
Item 6. A method for finely processing a Group 6 element-containing semiconductor material according to Item. 7. A Group 6 element-containing semiconductor material to be etched is zinc selenide, cadmium selenide, zinc sulfide,
The fine processing method for a Group 6 element-containing semiconductor material according to any one of claims 1 to 6, which is cadmium sulfide, zinc telluride, cadmium telluride, or a mixed crystal thereof. 8. The Group 6 element-containing semiconductor material to be etched is copper indium selenide, copper gallium selenide, copper aluminum selenide, silver gallium selenide, copper indium sulfide, copper gallium sulfide, copper aluminum sulfide, silver sulfide. The fine processing method for a semiconductor material containing a Group 6 element according to any one of claims 1 to 6, which is gallium or a mixed crystal thereof.