JP2012019230A - Plasma etching electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma etching electrode capable of preventing etching failures of a silicon wafer to improve a production yield of a semiconductor integrated circuit, and drastically reducing metal contamination of the silicon wafer immediately after starting the use.SOLUTION: A plasma etching electrode is formed of glassy carbon with an Fe contamination amount to a silicon wafer surface being 1×10atoms/cmto 10×10atoms/cm. It is preferred that a thickness of the plasma etching electrode is 3-10 mm.

Description

  The present invention relates to an electrode (hereinafter referred to as a plasma etching electrode) used in a plasma etching apparatus used for processing a semiconductor wafer, and more specifically, a high frequency power is applied to a reaction chamber and an etching gas is dispersed in a shower shape. The present invention relates to an electrode to which the high-frequency power is applied in a parallel plate type plasma etching apparatus or the like having an upper electrode having a gas blowing hole and a lower electrode on which a silicon wafer is placed facing the electrode.

  An etching process is performed in order to form elements on a semiconductor wafer. As an apparatus for performing this etching, 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 container 1 at an interval, and a silicon wafer 4 is mounted on the lower electrode 3 as a material to be processed. It is location. The upper electrode 2 is composed of a back plate 5 and a plasma etching electrode 6, and each is provided with a gas blowing hole 7 for flowing an etching gas.

  A plasma 11 is formed by applying a high-frequency power between the upper electrode 2 and the lower electrode 3 by a high-frequency power source 8 while flowing an etching gas toward the silicon wafer 4 through the gas blowing holes 7. The silicon wafer 4 is etched by this plasma to form elements having a predetermined pattern. The insulating ring 9 and the shield ring 10 are made of an insulator such as alumina or quartz, and the shield ring 10 covers the outer periphery of the plasma etching electrode 6 in order to protect the mounting screw for the plasma etching electrode 6 from plasma. Installed.

  As the plasma etching electrode 6 is used, a portion where plasma is generated, that is, a portion having substantially the same area as the silicon wafer 4 facing the plasma etching electrode 6 is etched and consumed by the plasma. Therefore, if the plasma etching electrode 6 is consumed to some extent and the etching characteristics (foreign particles adhering to the silicon wafer 4 during etching) deviate from the standard, the use of the plasma etching electrode 6 is stopped and replaced with a new electrode. .

Conventionally, as described in JP-A No. 62-109317, glassy carbon has been used by utilizing the property that carbon particles do not fall off and have high purity. However, with the recent high integration of semiconductor integrated circuits, the shape after etching of a silicon wafer has been controlled with higher accuracy, so that metal contamination that affects the yield of semiconductor integrated circuits (especially Fe Reduction of contamination is required. Along with this, the plasma etching electrode is also required to have less metal impurities.
As a countermeasure, the glass-etched carbon plasma etching electrode was purified to high purity by RCA cleaning used for cleaning silicon wafers. Metal contamination of the silicon wafer, particularly metal contamination immediately after the start of use of the plasma etching electrode was performed. Has not yet been improved significantly.

Moreover, the purity measuring method of the plasma etching electrode currently generally performed is as follows.
(1) After ashing the plasma etching electrode, the amount of impurities is measured by ICP-MASS of the ash.
(2) The plasma etching electrode is immersed in 10% hydrochloric acid to extract metal impurities adhering to the surface, and then the amount of metal impurities in the extract is measured by ion chromatography.

  However, in the measurement method of (1), the bulk purity of the plasma etching electrode is known, but since the measurement sensitivity is low, the correlation with the product yield of the semiconductor integrated circuit, particularly the yield immediately after use, was not known. In the measurement method (2), only the amount of impurities adhering to the surface can be measured. However, since the impurities adhering to the surface are easily removed by empty discharge (plasma is generated by introducing a dummy silicon wafer) performed when the electrodes are attached, the metal contamination of the silicon wafer is not affected. Therefore, there was no correlation between product yield and impurity content.

JP 62-109317 A

  The present invention provides a plasma etching electrode capable of preventing the etching failure of a silicon wafer and greatly reducing the production yield of a semiconductor integrated circuit and the metal contamination of the silicon wafer immediately after the start of use.

The present invention relates to a plasma etching electrode made of glassy carbon in which the amount of Fe contamination on a silicon wafer surface is 1 × 10 ¹⁰ atoms / cm ² to 10 × 10 ¹⁰ atoms / cm ² .
The present invention also relates to the plasma etching electrode as described above, wherein the plasma etching electrode has a thickness of 3 to 10 mm.

The plasma etching electrode of the present invention can prevent metal contamination after etching a silicon wafer, and can greatly reduce the production yield of a semiconductor integrated circuit and the production yield immediately after the start of use.
In addition, the plasma etching apparatus using the plasma etching electrode of the present invention prevents the metal contamination of the silicon wafer and greatly increases the production yield of the semiconductor integrated circuit, particularly immediately after the start of using the new plasma etching electrode. Can be reduced.
In the plasma etching electrode of the present invention, the metal contamination after etching of the silicon wafer can be prevented and the production yield of the semiconductor integrated circuit can be improved. In particular, the production process immediately after the use of a new plasma etching electrode is started. It is possible to accurately select a plasma etching electrode that can significantly reduce the yield.

It is the schematic of the plasma etching apparatus using the plasma etching electrode of this invention.

The present invention is a plasma etching electrode made of glassy carbon in which the amount of Fe contamination on the silicon wafer surface is 1 × 10 ¹⁰ atoms / cm ² to 10 × 10 ¹⁰ atoms / cm ² .
By controlling the Fe concentration measured by secondary ion mass spectrometry (SIMS) to 1 × 10 ³ counts or less in the plasma etching electrode in which the portion consumed by plasma is made of glassy carbon, the metal of the silicon wafer It has been found to significantly reduce contamination. Here, if the value measured by SIMS exceeds 1 × 10 ³ counts, the silicon wafer, which is the material to be etched, is contaminated by the scattered Fe as the electrode is consumed during plasma etching. The semiconductor integrated circuit that is present becomes defective.
Secondary ion mass spectrometry (SIMS) Fe concentration measured by, since be 5 × ¹⁰ 2 counts or less higher effect of production yield improvement of a semiconductor integrated circuit, and more preferably, 1 × ¹⁰ 2 counts or less and It is particularly preferable to do this.

  The shape of the plasma etching electrode in the parallel plate type plasma etching apparatus is generally a disc shape. In the present invention, the plasma etching electrode in which the portion consumed by the plasma is made of glassy carbon means that the whole disk is made of glassy carbon and the portion consumed by the plasma, that is, the central portion of the disk (the gas blowing hole is The range provided is made of glassy carbon, and the outer periphery thereof is composed of other materials.

If the glassy carbon which comprises the plasma etching electrode of this invention satisfy | fills the said characteristic, there will be no restriction | limiting in particular in the raw material and a manufacturing method.
Examples of the thermosetting resin used as a raw material include a phenol resin, an epoxy resin, an unsaturated polyester resin, a furan resin, a melamine resin, an alkyd resin, and a xylene resin. A mixture of these resins can also be used. Among these, furan resin or phenol resin is preferable.

A curing agent is used depending on the type of thermosetting resin. Examples of the curing agent include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, organic sulfonic acids such as p-toluenesulfonic acid and methanesulfonic acid, and carboxylic acids such as acetic acid, trichloroacetic acid and trifluoroacetic acid. The curing agent is preferably used in an amount of 0.001 to 20% by weight based on the thermosetting resin.
The thermosetting resin is added with the curing agent as necessary, and then molded by various molding methods according to the target shape, and then cured. This curing is preferably performed by heat treatment at a temperature of 60 to 200 ° C., more preferably 70 to 100 ° C.

  If necessary, after further processing as a plasma etching electrode plate, in a inert atmosphere (usually inert gas such as helium and argon, nitrogen, hydrogen, halogen, etc.) using a highly purified jig and furnace In a non-oxidizing gas or other oxygen-free atmosphere or under vacuum), the carbonization is preferably performed at a temperature of 800 to 3000 ° C., more preferably 1100 to 2800 ° C. Then, it is preferably heat treated at a temperature of 1300 to 3500 ° C. to obtain glassy carbon.

  A method for bringing the measured value of Fe by SIMS within the above range is not particularly limited, but a method of cleaning the plasma etching electrode with a strong acid such as hydrofluoric acid, concentrated sulfuric acid, or aqua regia added with a surfactant, HCl Examples include a method of performing a high-temperature heat treatment in a gas atmosphere.

  The size and shape of the plasma etching electrode of the present invention are not particularly limited, but a disk-shaped one having an outer diameter of 150 to 400 mm and a thickness of 3 to 10 mm is preferable. It is preferable that 8 to 24 mounting holes on the outer peripheral portion for mounting the electrode to the plasma etching apparatus are provided. It is preferable that the gas blowing holes for dispersing the etching gas in a shower shape are provided in the inner peripheral portion from the mounting holes. The size of the gas blowing hole varies depending on etching conditions and the like, but the hole diameter is preferably 0.3 to 2.0 mm, and the number of holes is preferably 100 to 3000. The hole can be processed by machining, electric discharge machining, ultrasonic machining, or the like.

The processing for forming the shape of the plasma etching electrode and the production of the gas blowing holes can be performed by electric discharge machining, ultrasonic machining, etc. after obtaining glassy carbon.
The plasma etching apparatus using the plasma etching electrode of the present invention is not particularly limited except that the above-described plasma etching electrode is used. As an example of the apparatus, the apparatus shown and described in FIG. 1 can be cited. In FIG. 1, the above-described plasma etching electrode may be used as the plasma etching electrode 6.
The plasma etching electrode evaluation method of the present invention can be performed by measuring the Fe concentration by the above-mentioned SIMS. As described above, if the conditions (manufacturing method, cleaning method, etc.) for obtaining the plasma etching electrode with an Fe concentration of 1 × 10 ³ counts or less are selected and the plasma etching electrode is manufactured thereby, the metal contamination of the silicon wafer can be prevented. It is possible to obtain a plasma etching electrode that can be reduced.

Examples of the present invention will be described below.
In addition, the SIMS measurement of a present Example was performed on the conditions of primary ion species: O2 ⁺ , primary ion acceleration voltage: 20KV, primary ion current: 300nA using Hitachi Ltd. IMA-3 type. .
The measured points were the center point of the glass-like carbon electrode and a total of 5 points of 4 points at a pitch of 90 ° at 10 mm from the outer periphery, and the average value was taken as the value of each electrode.

Examples 1-8
Phenol resin (trade name VP-112N, manufactured by Hitachi Chemical Co., Ltd.) is used as the raw material resin, and 8% by weight of trichloroacetic acid is added to this as a curing agent. Molded to obtain a resin plate. This resin plate was heat-cured at 70 ° C. for 3 days and 90 ° C. for 3 days, and then calcined at a maximum temperature of 900 ° C. at a rate of 1 ° C./min, and then at a maximum rate of 3000 ° C. at a rate of 5 ° C./min. To give glassy carbon. Gas discharge holes (hole diameter: 0.5 mm, pitch: 10 mm, number of 500 pieces) are formed on the obtained glassy carbon flat plate by electric discharge machining, and then surface-finished by lapping and polishing, and a plasma etching electrode (outer diameter: 200 mm, thickness) 3 mm).
Next, ultrasonic cleaning is performed by immersing in hydrofluoric acid in which a concentration of 26% by weight of hydrofluoric acid, a concentration of 60% by weight of nitric acid, and a surfactant (product name: Surflon S131, manufactured by Asahi Glass Co., Ltd.) is mixed 5: 5: 1 It was. The plasma etching electrode of the present invention was obtained by changing the ultrasonic cleaning time in the range of 30 minutes to 120 minutes and measuring with SIMS.

  The above-described plasma etching electrode is attached to the plasma etching apparatus having the configuration shown in FIG. 1, and 20 SCCM of trifluoromethane and fluorinated methane are flown as reaction gases, silicon power is supplied under conditions of a power supply frequency of 400 kHz and a gas pressure of 0.05 Torr in the reaction chamber The wafer was etched. Next, the amount of Fe contamination on the surface of the silicon wafer was measured with a total reflection fluorescent X-ray analyzer (manufactured by Technos Co., Ltd., model TREX610T). The measurement results are shown in Table 1.

Comparative Examples 1-4
Phenol resin (trade name VP-112N, manufactured by Hitachi Chemical Co., Ltd.) is used as the raw material resin, and 8% by weight of trichloroacetic acid is added to this as a curing agent. Molded to obtain four resin plates. This resin plate was heat-cured at 70 ° C. for 3 days and 90 ° C. for 3 days, and then calcined at a maximum temperature of 900 ° C. at a rate of 1 ° C./min, and then at a maximum rate of 3000 ° C. at a rate of 5 ° C./min. To give glassy carbon. Gas discharge holes and the like were formed on the obtained glassy carbon flat plate by electric discharge machining in the same manner as in the example, and then the surface was finished with lapping and polishing to form a plasma etching electrode. Next, ultrasonic cleaning was performed for 30 minutes with hydrochloric acid (concentrations of 1% by weight, 3% by weight, 7% by weight and 10% by weight), followed by further cleaning with pure water for 30 minutes. This was measured by SIMS to obtain a plasma etching electrode outside the scope of the present invention.

  The above plasma etching electrode is attached to the plasma etching apparatus in the same manner as in the examples, and 20 SCCM of trifluoromethane and fluorinated methane are flown as reaction gases, a silicon wafer under the conditions of a power supply frequency of 400 kHz and a gas pressure of 0.05 Torr in the reaction chamber. Etching was performed. Next, the amount of Fe contamination on the surface of the silicon wafer was measured with a total reflection fluorescent X-ray analyzer (manufactured by Technos Co., Ltd., model TREX610T). The measurement results are shown in Table 2. The measurement results of the amount of Fe contamination in Tables 1 and 2 show average values of 5 points in a 6-inch wafer.

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

Claims (2)

  A thermosetting resin added with 0.001 to 20% by weight of a curing agent is molded and cured, subjected to predetermined processing as a plasma etching electrode plate, and then at a temperature of 800 to 3000 ° C. in an inert atmosphere. A plasma etching electrode that is calcined and then heat treated at a temperature of 1300 to 3500 ° C.   The plasma etching electrode according to claim 1, wherein the plasma etching electrode has a thickness of 3 to 10 mm.

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