JPH09167697A - Plasma generating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate plasma in a stable condition by adding gas to generate an anion having atomic weight lighter than halogen type gas to halogen or halogen type gas being halogenated hydrogen. SOLUTION: Halogen or halogenated hydrogen is used as halogen type gas, and Cl2 is cited as a concrete example of halogen, and HBr is cited as a concrete example of halogenated hydrogen. Fe, N2 , H2 and O2 are used as gas to generate an anion having atomic weight lighter than halogen type gas. According to a plasma generating method constituted in this way, when gas to generate an anion having atomic weight lighter than the halogen type gas such as Fe, N2 , H2 and O2 is added to halogen such as Cl2 and HBr or halogenerated hydrogen, added gas plays a catalytic role, and as a result, discharge starting voltage is reduced, and plasma can be generated in a stable condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of generating high frequency plasma in a stable state in plasma generation using high frequency discharge.

[0002]

2. Description of the Related Art A plasma generation method using a high frequency discharge is used in various fields such as dry etching for fine processing in semiconductor devices and plasma CVD for forming a thin film. For high precision control of plasma, plasma generation in high vacuum is required.

Among them, plasma using various gases is used also in dry etching, for example, and the pressure is too low in plasma using high frequency.
If the capacity of the matching circuit cannot be sufficiently obtained, the discharge state of plasma becomes unstable, stable dry etching cannot be performed, and good fine processing cannot be realized. In particular, in the case of a halogen gas and a hydrogen halide gas alone, it is generally difficult to stabilize the discharge state of plasma.

A conventional plasma generation method will be described below. FIG. 1 shows the plasma generator used in the experiment. In the figure, 10 is a reaction chamber and 11, 12, 13 are three side electrodes for applying high frequency power. Side electrode 1
1, 12, 13 are connected to high-frequency power sources 14, 15, 16 for applying high-frequency power of 13.56 MHz or 54.24 MHz with their phases being shifted by 120 degrees, and confine electrons by a rotating electric field. High vacuum plasma is generated. Reference numeral 17 is a lower electrode, 18 is a high frequency power source for applying high frequency power of 13.56 MHz to the lower electrode 17, and 19 is a ground electrode.

Next, a method of generating plasma using this experimental apparatus will be described. First, a case where HBr single gas is used as the plasma generating gas will be described with reference to Tables 1 and 2.

[0006]

[Table 1]

[0007]

[Table 2]

Conventional Example 1: Plasma-generating gas is HBr single gas (residence time is 1.0 second), and 13.56 MHz is used for high frequency for plasma generation. Conventional Example 2: In order to increase the plasma density, HBr single gas was used as the plasma generating gas (residence time 1.0 second), and 54.24 MHz was used for the high frequency for plasma generation.

Conventional Example 3: In order to accelerate exhaustion of reaction products during dry etching, the residence time of HBr single gas is shortened to 0.4 seconds, and a high frequency for plasma generation is set to 13.5.
6 MHz was used. Conventional Example 4: In Conventional Example 3, the discharge gas pressure is 5 (mTorr
).

Next, a case where Cl ₂ single gas is used as the plasma generating gas will be described with reference to Table 3.

[0011]

[Table 3]

Conventional Example 5: Plasma generating gas was Cl ₂ single gas (residence time 1.0 second), and 54.24 MHz was used for high frequency for plasma generation. Conventional Example 6: The plasma generating gas is Cl ₂ single gas (residence time 0.1 seconds), and 54.24 M is applied to the high frequency for plasma generation.
Hz was used.

[0013]

When a discharge was generated in Conventional Example 1, a stable state was maintained from the initial stage of discharge start by visual observation, and plasma flicker did not occur even 5 minutes after start of discharge. When such conditions are applied to the fine processing of dry etching, the processing accuracy and reproducibility are good, and they can withstand practically enough.

However, when the discharge is set up in the conventional example 2, the plasma starts to flicker about 20 seconds after the start of the discharge by visual observation, and the unstable state continues thereafter. Under these conditions, when applied to fine processing such as dry etching,
Its processing accuracy and reproducibility are poor, and it is not practically endurable. As described above, when the frequency of the high frequency power is increased, there is a problem that plasma is difficult to generate.

When a discharge is generated in the conventional examples 3 and 4,
From visual observation, plasma began to flicker about 20 seconds after the start of discharge, and the unstable state continued. When applied to fine processing such as dry etching under such conditions, the processing accuracy and reproducibility are poor and it is not practically endurable. As described above, when the gas residence time is shortened, there is a problem that plasma is difficult to generate.

In addition, when the discharge is set up in Conventional Example 5, the plasma flickers about 20 seconds after the start of the discharge by visual observation, and the unstable state continues thereafter. Under these conditions, when applied to fine processing such as dry etching,
Its processing accuracy and reproducibility are poor, and it is not practically endurable. As described above, when the frequency of the high frequency power is increased, there is a problem that plasma is difficult to generate.

Further, when the discharge is set up in Conventional Example 6, the plasma flickers in about 20 seconds after the start of the discharge by visual observation, and the unstable state continues thereafter. Under these conditions, when applied to fine processing such as dry etching,
Its processing accuracy and reproducibility are poor, and it is not practically endurable. As described above, when the frequency of the high frequency power is increased and the residence time of the gas is shortened, there is a problem that plasma is difficult to generate.

As described above, when the plasma generating gas is a halogen gas or a hydrogen halide gas alone, there is a problem that the discharge is not always stable depending on the conditions of the plasma generation high frequency and the gas residence time. In view of the above problems, it is an object of the present invention to provide a plasma generation method capable of generating high frequency plasma in a stable state.

[0019]

According to the plasma generation method of the present invention, a gas that produces negative ions having an atomic weight lighter than that of the halogen-based gas is added to the halogen-based gas to generate plasma by high-frequency discharge. Note that halogen or hydrogen halide is used as the halogen-based gas, specifically Cl ₂ , HBr, or the like is used, and F ₂ or N ₂ is used as the gas that produces a negative ion having an atomic weight lighter than that of the halogen-based gas. , H ₂ , O _2, etc. are used.

According to the plasma generation method of the present invention, C
l ₂ , HBr or other halogen or hydrogen halide,
By adding a gas such as F ₂ , N ₂ , H ₂ or O ₂ which produces a negative ion having an atomic weight lighter than the halogen-based gas,
The added gas plays a catalytic role, and as a result, the discharge starting voltage is lowered, and plasma can be generated in a stable state.

[0021]

First, the plasma generator shown in FIG. 1 is used as an experimental device. In addition, plasma generated gas,
A mixed gas is used in which a gas that produces negative ions having an atomic weight lighter than the halogen-based gas is added to the halogen-based gas. Halogen or hydrogen halide is used as the halogen-based gas, and specific examples of halogen include Cl ₂ and specific examples of hydrogen halide include HBr.

Further, F ₂ , N ₂ , H ₂ and O ₂ are used as the gas which produces negative ions having an atomic weight lighter than the halogen-based gas. According to the plasma generation method thus configured, negative ions having a lighter atomic weight than halogen-based gas such as F ₂ , N ₂ , H ₂ and O ₂ are generated in halogen such as Cl ₂ and HBr or hydrogen halide. By adding the gas, the added gas plays a catalytic role, and as a result, the discharge starting voltage is lowered. Therefore, the frequency of the high frequency power supply is 5
Plasma can be generated in a stable state even when the frequency is 0 MHz or more and the gas residence time is 0.4 seconds or less.

Although HBr and Cl ₂ are exemplified as the halogen-based gas in the above-mentioned embodiment, it is needless to say that the same effect can be obtained with a halogen-based gas other than these. Although F ₂ , N ₂ , H ₂ and O ₂ have been exemplified as the gas having the negative ions with the atomic weight lighter than that of the halogen-based gas, other gases that generate the negative ions with the atomic weight lower than those of the halogen-based gas can be used. It goes without saying that the same effect can be obtained.

[0024]

EXAMPLES Examples will be described with reference to Table 4.

[0025]

[Table 4]

Example 1 A mixed gas in which H ₂ is added to Cl ₂ gas as a plasma generating gas (residence time: 1.0 second)
Then, 54.24 MHz is used for the high frequency for plasma generation. Other conditions are the same as those in Conventional Example 5 (Table 3).
When the discharge was started under these conditions, the stable state was maintained from the initial stage of the discharge by visual observation, and the flicker of the plasma did not occur even 5 minutes after the start of the discharge. When such conditions are applied to the fine processing of dry etching, the processing accuracy and reproducibility are good, and they can withstand practically enough.

As described above, by adding the gas (H ₂ ) that produces negative ions to the halogen-based gas (Cl ₂ ), the added gas (H ₂ ) plays a catalytic role, and as a result, the discharge start voltage is increased. Decreased, and high frequency for plasma generation was 54.24M
Plasma is generated in a stable state even when the frequency is increased to Hz. Example 2: The plasma generating gas is a mixed gas (residence time 0.4 seconds) formed by adding O ₂ to HBr gas, and 13.56 MHz is used for the high frequency for plasma generation. Other conditions are the same as those in Conventional Example 4 (Table 2). When the discharge was started under these conditions, the stable state was maintained from the initial stage of the discharge by visual observation, and the flicker of the plasma did not occur even 5 minutes after the start of the discharge. When such conditions are applied to the fine processing of dry etching, the processing accuracy and reproducibility are good, and they can withstand practically enough.

As described above, by adding the gas (O ₂ ) which produces negative ions to the halogen-based gas (HBr), the added gas (O ₂ ) plays a catalytic role, and as a result, the discharge starting voltage is lowered. However, the residence time of the plasma-generated gas is 0.4
Even if it is as short as a second, plasma is generated in a stable state. Example 3: The plasma generating gas is a mixed gas of Cl ₂ gas and O ₂ added (residence time 0.1 second), and 54.24 MHz is used for the high frequency for plasma generation. The other conditions are the same as in Conventional Example 6 (Table 3). When the discharge was started under these conditions, the stable state was maintained from the initial stage of the discharge by visual observation, and the flicker of the plasma did not occur even 5 minutes after the start of the discharge. When such conditions are applied to the fine processing of dry etching, the processing accuracy and reproducibility are good, and they can withstand practically enough.

As described above, by adding the gas (O ₂ ) that produces negative ions to the halogen-based gas (Cl ₂ ), the added gas (O ₂ ) plays a catalytic role, and as a result, the discharge start voltage is increased. Decreased, and high frequency for plasma generation was 54.24M
And the plasma generation gas residence time is 0.1
Even if it is as short as a second, plasma is generated in a stable state.

[0030]

According to the plasma generation method of the present invention,
By adding a halogen or hydrogen halide such as Cl ₂ or HBr to a gas that produces a negative ion having an atomic weight lighter than that of a halogen-based gas such as F ₂ , N ₂ , H ₂ or O ₂ , the added gas becomes catalytic. Plays a role, and as a result, the discharge starting voltage decreases. Therefore, the frequency of the high frequency power supply is 50
The effect that plasma can be generated in a stable state is obtained even in the case of MHz or more and the condition that the gas residence time is 0.4 seconds or less.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a plasma generator.

[Explanation of symbols]

 10 Reaction Chamber 11, 12, 13 Side Electrodes 14, 15, 16, 18 High Frequency Power Supply 17 Lower Electrode 19 Ground Electrode

Claims (4)

[Claims] 1. A plasma generation method in which a gas generating negative ions having an atomic weight lighter than that of the halogen-based gas is added to the halogen-based gas, and plasma is generated by high-frequency discharge. 2. The plasma generation method according to claim 1, wherein the halogen-based gas is halogen or hydrogen halide. 3. The halogen-based gas is Cl ₂ or HB
2. The plasma generation method according to claim 1, wherein r is r. 4. The plasma generation method according to claim 1, 2 or 3, wherein the gas generating negative ions having an atomic weight lighter than the halogen-based gas is F ₂ or N ₂ or H ₂ or O ₂ .