JPH07169756A - Plasma etching method - Google Patents

Abstract

PURPOSE:To provide a plasma etching method by which such a substance or gas that is not required for etching is generated nor such a substance or gas that gives a trouble to the etching device is not generated. CONSTITUTION:After a substrate 3 to be etched is set on a sample stage 4 in a reaction vessel 1, selective etching is performed in a pattern by supplying a plasma of a reactive gas. A nitrogen chloride gas or nitrogen fluoride gas is used as the reactive gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching method using a compound of nitrogen and a halogen element as a reactive gas for plasma etching. In recent years, for example, dry etching using a reactive gas is being developed as an etching technique used in a manufacturing process of a semiconductor integrated circuit, instead of conventional wet etching using an etching solution.

[0002]

2. Description of the Related Art This dry etching is characterized in that the process can be simplified and the reliability of the device can be improved. Therefore, the etching gas decomposes halogen compounds such as CF ₄ and CCl ₄ which are compounds of fluorine and chlorine in plasma to generate F ^* and Cl ^* . For example, a gas etching apparatus described in Japanese Patent Publication No. 53-14472, supplies a gas containing fluorine atoms into a vacuum container containing a sample and dissociates the gas to generate a plasma etching gas. Etching is performed with this plasma etching gas.

Further, the dry etching apparatus described in JP-A-53-96938 discloses that a microwave is absorbed in a vacuum vessel containing a sample to generate an electric discharge and a magnetic field, and at the same time, CF is used. ₄ and oxygen, or C ₂ C
A plasma etching gas is generated by supplying l ₂ and oxygen, and etching is performed using this plasma etching gas. Further, the processing apparatus using a gas containing hydrogen fluoride described in JP-B-55-8592 produces an etching gas by supplying a gas containing hydrogen fluoride into a vacuum container in a cooled state. Even if plasma treatment is not performed in advance, etching is performed with this etching gas.

[0004]

However, the plasma etching gas in the inventions described in the above publications contains carbon which is solid or an oxidizing gas, which is extremely harmful from the viewpoint of improving the reliability of the semiconductor. It turned out to be Therefore, 0.1% is added to the CF ₄ and CCl ₄ gas.
Add 5% to 5% oxygen, combine carbon and oxygen,
It is considered to use CO ₂ gas. But,
In this plasma, the combination of carbon and oxygen is not always sufficient, and it is basically an unsuitable gas for semiconductor integrated circuits, or in the activated state such as carbon or oxygen. It may remain. As a plasma etching method that does not use carbon, there is a method that uses HCl. The above-mentioned gas is extremely acidic, and the reaction container, the handle, the vacuum pump, etc. are easily corroded, which has become another big problem.

In order to solve the above problems, it is an object of the present invention to provide a plasma etching method which does not generate a substance or gas unnecessary for etching or a substance or gas unfavorable to an etching apparatus.

[0006]

In order to achieve the above object, the plasma etching method of the present invention comprises a reaction vessel (1)
The substrate (3) to be etched is disposed on the sample table (4), and the reactive gas converted into plasma is supplied to selectively etch the pattern. It is characterized in that it is composed of a nitrogen chloride gas or a fluoride fluoride gas.

[0007]

[Operation] The applicant is a chemically stable gas,
When activated or decomposed, halogen elements and their by-products are harmless gases such as nitrogen halides, especially fluorinated nitrite gases (NF, NF ₂ , NF ₃ ) and chlorinated nitrite gases (NCl, NCl). ₂ , a plasma etching method using NCl ₃ ) was discovered. Further, the applicant of the present invention has found that this NF, an ammonium chloride fluoride (NH ₄ F, NH ₄ HF ₂ ) which is a hydride of NCl.
, Ammonium chloride (NH ₄ Cl) solid is activated and decomposed in plasma, stable gas of N ₂ and NH ₃ and fluorine,
It was discovered to generate chlorine radicals. Plasma etching using the above reactive gas can perform highly reliable processing without leaving unnecessary solids or gas for plasma etching.

[0008]

EXAMPLE FIG. 1 is a diagram for explaining a vertical plasma etching apparatus according to an example of the present invention. In FIG. 1, the plasma etching apparatus includes an etching container (1)
And a microwave generation source (6), a gas supply system, and an exhaust system. And the etching container (1) is
It is provided with an electrode (2), a sample table (4) on which a sample (3) is placed, and an active chamber (5) for activating a reactive gas. The gas supply system consists of an inlet (9) for supplying reactive gas NF ₃ to the etching container (1) and an inlet (10) for supplying hydrogen or an inert gas to the etching container (1). Has been done.
Microwave source (6) is an attenuator from a magnetron with a frequency of 2.45GHz and maximum capacity of 1.35KW.
The reactive gas is activated in the activation chamber (5) via (7). The exhaust system consists of a stop valve (11) and a needle valve (12).
And a rotary pump (13).

In the plasma etching apparatus as described above, the reactive gas reacts as follows. NF ₃ → N ^* + 3F ^* 2N ^* → N ₂ ↑ F ^* + Si → SiF ₄ ↑ The sample to be etched by the above reaction is a single crystal,
In polycrystalline, amorphous, or semi-amorphous silicon, radical fluorine etches the sample as SiF ₄ . Further, radical nitrogen is stable and is released as an inert gas (N ₂ ) that does not bond with other substances. The material to be etched may be another silicide such as silicon nitride, aluminum oxide, silicon oxide or the like.

The pressure in the reaction vessel is controlled by the exhaust valve stop valve (11), needle valve (12) or rotary pump (13).
It was adjusted by. To selectively oxidize the substrate or the coating on the substrate, use a photoresist such as OMR83 (manufactured by Tokyo Ohka).
It suffices to form a slit opening of 1 μm in size by using a resist pattern and etch only the opening. The pressure of the container during etching was 0.01 torr to 0.5 torr, but generally 0.05 torr to 0.5 torr could cut the fine pattern without side etching. Sample (3) is 100
The temperature range was controlled to -30 ° C to -30 ° C. Especially the sample
(3) is 10 ° C to -15 ° C through the sample stage (4) when etching silicon oxide with 1% to 10% hydrogen.
It is better to cool down the pattern because the pattern will be removed
It was possible to reduce it to 2000Å / min or 300Å / min, and the etching result was beautiful.

Further, when nitrogen chloride is used as the halogen element, it is preferable for etching a metal such as aluminum, molybdenum, or tungsten, or a compound thereof, and the reaction formula in the case of aluminum is shown below. NCl ₃ → N ^* + 3Cl ^* 2N ^* → N ₂ 4Cl ^* + Al → AlCl ₄ ↑ In addition, hydrogen may be added in an amount of 0.1% to 10% to improve the cutting of the pattern. Furthermore, in this example, solids such as powder NH ₄ F, NH ₄ HF ₂ are placed in the active chamber (5), and at the same time, an inert gas such as He and Ar is introduced from (10),
Fluorine radicals may be generated by activating and decomposing this ammonium fluoride by microwaves. Further, the generated radicals and the by-products collide with the upper surface of the sample (3) by He and Ar, and it is possible to selectively etch it.

This is also the case with ammonium chloride. The present invention has shown plasma etching of silicon or its compounds. However, the same applies to plasma etching of GaAs, InP, BP, etc., and further applicable to oxides and nitrides thereof. Further, the plasma etching system is not limited to microwaves, but also applies to high-frequency waves of 13.56 MHz, and the same applies to capacitive coupling type, inductive coupling type, and parallel plate type etching techniques. Needless to say, this reactive gas may be used for sputter etching or reactive sputter etching.

[0013]

According to the present invention, since a chlorinated nitride gas or a fluorinated nitrite gas is used as the plasma etching gas, the etching pattern is well cut off and the plasma etching is unstable. Solids or gases that easily bind to other substances are not generated.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a vertical plasma etching apparatus according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Etching container 2 ... Electrode 3 ... Sample (substrate) 4 ... Sample stand 5 ... Active chamber 6 ... Microwave source 7 ... Attenuator 9 ... NF ₃ Inlet port 10 ··· Hydrogen, oxygen, inert gas inlet port 11 ··· Stop valve 12 ·· Needle valve 13 ·· Rotary pump

Claims (1)

[Claims] 1. A plasma etching method in which a substrate to be etched is provided on a sample table in a reaction container, and a reactive gas that has been turned into plasma is supplied to selectively etch a pattern. Is a chlorinated nitrite gas or a fluorinated nitrite gas, which is a plasma etching method.