JP2000164568A - Manufacture of plasma etching electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove heavy metal by a method wherein the mirror surface finishing of a glassy carbon plasma etching electrode is carried out by the use of a polishing solution which contains silicon oxide particles, and the plasma etching electrode is cleaned with hydrofluoric acid or a mixed acid that contains hydrofluoric acid. SOLUTION: The surface of a glass plasma etching electrode exposed to plasma is subjected to mirror surface finishing so as to be as high in surface smoothness as prescribed. A polishing solution used for mirror surface finishing of the plasma etching electrode contains 0 to 50 wt.% SiO2 particles which are preferably about 5 to 100 nm in grain diameter. Thereafter, the etching electrode is cleaned with a hydrofluoric acid or a mixed acid that contains a hydrofluoric acid. At this point, it is preferable that 10 to 26 wt.% hydrofluoric acid is used. It is preferable that the etching electrode is rinsed with pure water after it is cleaned with hydrofluoric acid. It is preferable that a cleaning operation is carried out through a manner where the electrode is dipped into a cleaning solution and subjected to ultrasonic cleaning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode of a plasma etching apparatus used for processing a semiconductor wafer.
It is called a plasma etching electrode. )). More specifically, a parallel plate plasma having an electrode to which high-frequency power is applied and having a gas blowing hole for dispersing an etching gas in a shower shape, and an electrode on which a silicon wafer is placed opposite to the electrode. The present invention relates to a method for manufacturing an electrode to which high-frequency power is applied in an etching apparatus.

[0002]

2. Description of the Related Art Etching is performed to form elements on a semiconductor wafer. As an apparatus for performing this etching process, a plasma etching apparatus is used. In the plasma etching apparatus, as shown in FIG. 1, an upper electrode 2 and a lower electrode 3 are provided in a vacuum vessel 1 at an interval, and a silicon wafer 4 is mounted on the lower electrode 3 as a material to be processed. Is placed.

The upper electrode 2 is composed of a back plate 5 and a plasma etching electrode 6, each of which is provided with a gas outlet 7 for flowing an etching gas.

While flowing an etching gas toward the silicon wafer 4 through the gas blowing hole 7,
Thereby, high-frequency power is applied between the upper electrode 2 and the lower electrode 3 to form the plasma 11. The silicon wafer 4 is etched by this plasma to form a predetermined pattern.

[0005] The shield ring 9 is made of an insulating material such as alumina or quartz, and is provided so as to cover the outer peripheral portion of the plasma etching electrode 6 in order to protect the screw 10 for mounting the plasma etching electrode 6 from plasma.

As the plasma etching electrode 6 is used, a portion where plasma is generated, that is, a portion having almost the same area as the silicon wafer 4 facing the plasma etching electrode 6 is etched and consumed by the plasma. Then, when the plasma etching electrode 6 is consumed to some extent and the etching characteristics (the amount of foreign particles or the like adhering to the silicon wafer 4 during the etching) deviate from the standard, the use of the plasma etching electrode 6 is stopped and a new one is used. Replace with an electrode.

Conventionally, as a plasma etching electrode,
As described in JP-A-62-109317, glassy carbon is used by utilizing the property that carbon particles do not fall off and have high purity. However, with the recent increase in the degree of integration of semiconductor integrated circuits, the shape of silicon wafers after etching has been controlled with higher precision, and the lifetime of silicon wafers has a correlation with the yield of semiconductor integrated circuits. The recovery rate (the time until the minority carriers generated by irradiation of light or the like in the silicon wafer disappear) has been controlled more strictly. Accordingly, it is required to reduce impurities in the plasma etching electrode which affect the lifetime recovery rate. As a countermeasure, RCA cleaning, which is used for cleaning silicon wafers, was applied to increase the purity of the plasma etching electrode. However, the lifetime recovery rate of semiconductor integrated circuits, especially the lifetime recovery rate immediately after the start of plasma etching electrode use, was significantly increased. It has not been improved yet.

[0008] As a result of investigating the cause, it has been found that a polishing liquid containing alumina particles as a main component is usually used for the mirror finish of the plasma etching electrode. Yes,
It was found that heavy metals such as Fe and Cr were firmly attached together with the abrasive grains. It is considered that heavy metals such as Fe and Cr could not be removed by ultrasonic cleaning or RCA cleaning with an organic solvent and pure water.

[0009]

SUMMARY OF THE INVENTION The present invention provides a plasma etching electrode capable of preventing metal contamination during etching of a silicon wafer and greatly improving the lifetime recovery rate of a semiconductor integrated circuit, especially the lifetime recovery rate immediately after use. The purpose is to provide.

[0010]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and as a result, the glass-like carbon plasma etching electrode has been mirror-finished with a polishing liquid containing SiO ₂ particles. By performing the subsequent cleaning using hydrofluoric acid or a mixed acid containing hydrofluoric acid, it is possible to remove the abrasive grains firmly penetrating the electrode surface and the heavy metal adhering thereto together with the abrasive grains. The inventors have found that high purification can be achieved, and have completed the present invention based on this finding.

That is, according to the present invention, the surface of the glass-etched carbon plasma etching electrode exposed to plasma is made of SiO 2.
_{The present} invention relates to a method for manufacturing a plasma etching electrode, which comprises mirror-finishing a polishing liquid containing _two particles and then cleaning the mirror-finished surface with hydrofluoric acid or a mixed acid containing hydrofluoric acid.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The glass-like carbon electrode for plasma etching of the present invention can be obtained, for example, by molding and curing a liquid thermosetting resin, followed by carbonization in an inert atmosphere and high-temperature treatment.

After the thermosetting resin is formed into a predetermined shape at a predetermined temperature, it is cured at a temperature of 130 to 200 ° C.
The thermosetting resin is not particularly limited, but furan resin,
Phenol resin, epoxy resin, unsaturated polyester resin, melamine resin, alkyd resin, xylene resin and the like can be mentioned. Further, a mixture of the above resins may be used. Preferably, it is a phenol resin and / or a furan resin. The thermosetting resin is molded according to the desired shape, but the molding method is not particularly limited.

Next, after a predetermined process such as a gas blowing hole or the like is performed to form a plasma etching electrode, a high-purity jig and a furnace are used in an inert atmosphere (usually an inert gas such as helium or argon). In an oxygen-free atmosphere composed of at least one kind of gas such as a gas, nitrogen, hydrogen, and a non-oxidizing gas such as a halogen gas, under reduced pressure or vacuum), it is preferably calcined at a temperature of 800 to 1200 ° C. and carbonized.
Next, high-temperature treatment is preferably performed at a temperature of 1700 ° C. or more to obtain a glass-like carbon plasma etching electrode.

As a method of obtaining a plasma etching electrode, other than the above-described method, after obtaining a glassy carbon original plate, a predetermined process such as a gas blowing hole may be performed by electric discharge machining or ultrasonic machining.

In order to form a plasma-etched electrode of a product, at least the surface of the electrode exposed to plasma is mirror-finished to a predetermined surface smoothness, and then washed.

In the present invention, SiO ₂ is used as a polishing liquid for mirror-finishing a plasma etching electrode.
A polishing liquid containing particles is used. The particle size of the SiO ₂ particle content and SiO ₂ particles of polishing liquid is not particularly limited as long as it is mirror-finished plasma etching electrode surface during normal alkaline aqueous solution (preferably, in NH ₄ OH, etc. (pH adjusted to 10 to 11) and preferably containing 10 to 50% by weight of SiO ₂ particles having a particle size of preferably 5 to 100 nm.

In the present invention, hydrofluoric acid or a mixed acid containing hydrofluoric acid is used for cleaning. The acid used in the cleaning step is the S that has firmly penetrated the plasma etching electrode surface.
This is for dissolving and removing the iO ₂ particles, and hydrofluoric acid alone or a mixed acid containing hydrofluoric acid, for example, a mixed acid of hydrofluoric acid and hydrochloric acid, sulfuric acid, nitric acid or the like is used. To complete the cleaning in a short time, the concentration of hydrofluoric acid is preferably higher,
There is no particular limitation. Preferably a concentration of 10 to 2
6% by weight hydrofluoric acid is used. After washing with an acid, washing with pure water is preferred. The washing operation is preferably performed by immersion in a washing solution and ultrasonic washing.

The size and shape of the electrode of the present invention are as follows.
Although not particularly limited, it is preferably circular and has an outer diameter of 150 to
Those having a thickness of 400 mm and a thickness of 3 to 10 mm are preferred. The size of the gas blowout hole provided in the center, preferably in a circular range, varies depending on the etching conditions and the like, but the hole diameter is preferably 0.3 to 2.0 mm, and the number of holes is 100 to 300.
Zero is preferred.

According to the method of the present invention, since the abrasive grains that have firmly penetrated the plasma etching electrode surface can be easily removed, metal impurities can be eliminated.

[0021]

The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

EXAMPLE A phenol resin (trade name: VP-112N, manufactured by Hitachi Chemical Co., Ltd.) was used as a raw material resin, and trichloroacetic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was used as a curing agent. Then, the mixture was cast into an aluminum petri dish having a diameter of 500 mm under heating at 70 ° C. to obtain a resin plate. After heating and curing this resin plate at 70 ° C. for 3 days and at 90 ° C. for 3 days, 1 ° C. /
The carbonized carbon was calcined at a maximum temperature of 900 ° C. at a heating rate of 1 minute, and then heat-treated at a maximum temperature of 3000 ° C. at a heating rate of 5 ° C./min to obtain a glassy carbon flat plate (203 mm in outer diameter and 3 mm in thickness).
After forming gas blowing holes (2000 pieces of φ0.8 mm) and the like in the obtained glassy carbon flat plate by electric discharge machining,
The main component is iO ₂ particles (particle size: 30 to 50 mm) (S
A mirror-finished polish solution (40% by weight of iO ₂ content) with a polishing liquid (manufactured by Fujimi Incorporated, an alkaline aqueous solution of pH 10; trade name: COMPOL 50) was used to form a plasma etching electrode. The mirror finish was performed using a double-side polishing machine (model DSM-18B) manufactured by Speed Fam Co., Ltd. under the conditions of a rotation speed of 35 rpm, a surface pressure of 1 kg / cm ² , and a polishing liquid supply amount of 10 cc / min. Then concentration 2
The substrate was immersed in 6% hydrofluoric acid and subjected to ultrasonic cleaning for 10 minutes, followed by ultrasonic cleaning with pure water for 15 minutes.

The above-mentioned plasma etching electrode was attached to a plasma etching apparatus, and trifluoromethane and fluorinated methane were supplied as reaction gases at a flow rate of 20 SCCM, respectively, at a power supply frequency of 400 KHz and a gas pressure of 0.05 in the reaction chamber.
The silicon wafer was etched under the condition of Torr. Next, the lifetime of this silicon wafer was measured with a lifetime measuring device manufactured by Leo Giken. Table 1 shows the measurement results.
Shown in

Comparative Example 1 A phenol resin (VP-112N, manufactured by Hitachi Chemical Co., Ltd.) was used as a raw material resin, and trichloroacetic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was used as a hardening material. 8% by weight was added thereto, and the mixture was cast into an aluminum petri dish having a diameter of 500 mm under heating at 70 ° C. to obtain a resin plate. After heating and curing this resin plate at 70 ° C. for 3 days and at 90 ° C. for 3 days, 1 ° C. /
And then heat-treated at a maximum temperature of 5 ° C./min at a maximum of 3000 ° C. to obtain a glassy carbon flat plate. After gas discharge holes and the like are formed in the obtained glassy carbon flat plate by electric discharge machining, the surface is mirror-finished with a polishing liquid containing alumina particles as a main component (trade name: A # 1000, manufactured by Fujimi Incorporated), and the shape of the plasma etching electrode is obtained. And The mirror finishing conditions were the same as in Example 1. Next, the substrate was immersed in hydrofluoric acid having a concentration of 26% and subjected to ultrasonic cleaning for 10 minutes, and further subjected to ultrasonic cleaning with pure water for 15 minutes.

The above-mentioned plasma etching electrode was attached to a plasma etching apparatus, and a silicon wafer was etched in the same manner as in Example 1. Next, the lifetime of this silicon wafer was measured with a lifetime measuring device manufactured by Leo Giken. Table 1 shows the measurement results.

Comparative Example 2 Gas discharge holes and the like were formed in a glassy carbon flat plate obtained in the same manner as in Comparative Example 1 by electric discharge machining, and then a polishing liquid containing SiO ₂ particles as a main component (manufactured by Fujimi Incorporated, a commercial product) Name: Compol 50) and mirror-finished to form a plasma etched electrode. Then, the substrate was immersed in hydrochloric acid having a concentration of 35% and subjected to ultrasonic cleaning for 10 minutes, and further subjected to ultrasonic cleaning with pure water for 15 minutes.

The above-mentioned plasma etching electrode was attached to a plasma etching apparatus, and a silicon wafer was etched in the same manner as in Example 1. Next, Table 1 shows the measurement results obtained by measuring the lifetime of the silicon wafer with a lifetime measuring device manufactured by Leo Giken.

[0028]

[Table 1] In addition, the lifetime measurement results in Table 1 show an average value of five points in a plane of a 6-inch wafer.

[0029]

When etching is performed using the plasma etching electrode of the present invention, there is no metal contamination.
The production yield of semiconductor integrated circuits is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a plasma etching apparatus using an electrode of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Upper electrode 3 Lower electrode 4 Silicon wafer 5 Back plate 6 Electrode 7 Gas blowout hole 8 High frequency power supply 9 Shield ring 10 Mounting screw 11 Plasma

Claims (1)

[Claims] 1. A method in which a surface of a glass-like carbon plasma etching electrode exposed to plasma is mirror-finished with a polishing liquid containing SiO ₂ particles, and then the mirror-finished surface is washed with hydrofluoric acid or a mixed acid containing hydrofluoric acid. A method for manufacturing a plasma etching electrode, which is characterized by