JP2004158226A - Graphite material for ion implanting apparatus and graphite member for ion implanting apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a graphite material for an ion implanting apparatus in which an erosion and a particle drop in the case of irradiating with an ion beam are few. <P>SOLUTION: In the graphite material for the ion implanting apparatus, a measured value by an ACT-JP method is 0.2 g/mm<SP>3</SP>or more. <P>COPYRIGHT: (C)2004,JPO

Description

【００２７】
表１中、耐熱衝撃係数（ｋＷ／ｍ）は引張り強さ（ＭＰａ）、熱伝導率（Ｗ／ｍ・Ｋ）、室温〜４００℃までの熱膨張係数（×１０^−６／℃）、弾性係数（ＧＰａ）から算出した。
熱伝導率はレーザーフラッシュ法（熱拡散率熱定数測定装置（真空理工（株）製））で熱拡散定数を測定し、この測定値と室温における比熱０．６９５Ｊ／ｇ・Ｋとから算出した。
熱膨張係数（×１０^−６／℃）は理学電機株式会社製熱機械分析装置（ＴＭＡ８３１０）で室温〜４００℃までの熱膨張係数を求めた。
弾性係数（ＧＰａ）は日本工業規格（ＪＩＳ）Ｒ−７２２２−１９９７に準じて求めた。
弾性係数（ＧＰａ）はＪＩＳ Ｒ７２０２−１９７９に準じて求めた。
脱落した黒鉛粒子の大きさは走査型電子顕微鏡で観察し求めた。
イオン注入装置中の発塵性はパーティクルカウンターで測定し、黒鉛粒子の数の多いものから順に×、△、○、◎とした。
【００２８】
表１から本発明に係る黒鉛材料は比較例の黒鉛材料に比べて消耗する黒鉛粒子が少なく、脱落する黒鉛粒子径もが小さい。しかも黒鉛部材から脱落した黒鉛粒子によるイオン注入装置内の発塵も少ないことが判る。
【００２９】
【発明の効果】
本発明では各粉砕工程の粒子径を制御したので、黒鉛粒子間の結合力が強い黒鉛材料が得られる。その結果、黒鉛部材の消耗が少なく、しかも脱落する黒鉛粒子径を小さくできる。したがって、ウエハー基板あるいはイオン注入装置内部の発塵を低減できる。
【図面の簡単な説明】
【図１】イオン注入装置の概略図である。
【図２】ＡＣＴ−ＪＰ法を示す概略図である。
【符号の説明】
１ 制御用マイクロコンピューター
２ ウエハー装着
３ カセット
４ 分離用電源
５ 分離用電磁石
６ 加速電極
７ シャッタ
８ シリコンウエハー基板
９ ビームストップ
１０ 偏向用電極
１１ 引き出し電極
１２ 電流計
１３ イオン源
１４ 高圧電源
１５ 真空ポンプ
２１ 黒鉛材料試験片
２２ 噴射ノズル[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a graphite material for an ion implanter and a graphite member for an ion implanter using the same. More specifically, the graphite material is less consumed by ion beam irradiation (erosion), and the size of the graphite particles is reduced even when the graphite particles fall off. The present invention relates to a graphite material for a small ion implanter and a graphite member for the ion implanter using the graphite material.
[0002]
[Prior art]
As a process for manufacturing a semiconductor device, there is a step of ion-implanting an impurity element into a semiconductor wafer substrate such as silicon, silicon carbide (SiC), gallium arsenide (GaAs), or gallium nitride (GaN) serving as a substrate. FIG. 1 shows a schematic view of the ion implantation apparatus.
[0003]
The ion implantation apparatus is an apparatus for ionizing a target impurity element, accelerating the ion to an energy of several tens to several hundreds eV, and implanting the energy into a wafer substrate. The ion implanter includes an ion generator for generating ions by converting a gas containing a target impurity element into a plasma state, an ion extractor for extracting the generated ions, and an ion analyzer for selecting the extracted ions to target ions. An ion accelerating unit for accelerating the ions, an ion converging unit for converging the accelerated ions, and an ion implanting unit for implanting an ion beam into the wafer substrate.
[0004]
As a material constituting each part of the ion implantation apparatus, a high-purity material having excellent heat resistance and thermal conductivity, less consumption (erosion) by an ion beam, and a low impurity content is required. It is disclosed in Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4 that a high-purity graphite material and a graphite material in which a coating of pyrolytic carbon or glassy carbon is formed on the surface of the high-purity graphite material are usually used. Have been.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 7-302568 [Patent Document 2]
JP-A-8-171883 [Patent Document 3]
Japanese Patent Application Laid-Open No. 2000-128640 [Patent Document 4]
Japanese Patent Application Laid-Open No. 2000-323052
As the internal components of the ion implantation apparatus, for example, graphite materials are used for flight tubes, various slits, electrodes, electrode covers, guide tubes, beam stops, and the like.
[0007]
However, since the above-described graphite material is obtained by sintering coke and a binder as an aggregate, when used as a member for an ion implantation apparatus, graphite particles are dropped by an ion beam and contaminate the inside of the ion implantation apparatus. In addition, there is a problem that the yield of semiconductor devices is reduced by mixing in the wafer substrate. There is also a problem that the graphite member is consumed by the irradiation of the ion beam.
[0008]
In particular, in recent years, the degree of integration of an integrated circuit (IC) has been improved, and the line width at the time of patterning has been reduced. In addition, the number of cases of irradiating a wafer substrate with a heavy metal ion beam such as arsenic (As) is increasing. Graphite particles generated at this time adhere to the wafer substrate and inhibit ion implantation, and damage to the wafer substrate due to high-hardness fine particles in which silicon and graphite particles are combined has become a more serious problem than ever before. .
[0009]
[Problems to be solved by the invention]
Accordingly, it is an object of the present invention to provide a graphite material for an ion implantation apparatus that is less consumed by an ion beam and the graphite particles fall off, and has a small graphite particle size even when the graphite particles fall off.
[0010]
[Means for Solving the Problems]
Then, the present inventors investigated the cause of wear of the graphite member for the ion implantation apparatus and the size of the falling particles. As a result, it has been found that when coarse particles having a large particle diameter are mixed in the pulverized powder, the bonding force between the particles is greatly reduced, which is likely to cause abrasion. In addition, it was found that the graphite particles fell off in units of pulverized powder (hereinafter referred to as pulverized powder) pulverized after kneading. Thus, it has been found that a graphite material having a small particle diameter of the graphite particles which is less consumed and falls off can be obtained by making the particle size uniform in each step. At this time, the bonding force between the graphite particles can be expressed as a measured value by the ACT-JP method, and it has been found that a graphite material that can solve the above problem can be manufactured by considering the measured value. It has been reached. That is, the gist of the invention according to claim 1 is a graphite material for an ion implantation apparatus whose measured value by the ACT-JP method is 0.2 g / mm ³ or more.
[0011]
The ACT-JP method is called an Arata Coating Test with Jet Particles method, and is a type of injection test method. For example, ceramic particles are sprayed onto the sprayed coating at different irradiation speeds and irradiation angles, and the degree of wear (weight loss) under each condition is measured. It is a method to evaluate. FIG. 2 shows a schematic diagram of the ACT-JP method. Although the production method differs between a general graphite material and a thermal spray coating, these can be regarded as being the same when particles are bonded. From the wear mechanism in the ACT-JP method, the wear rate of the test piece is detected as a bonding force between particles. And, the wear rate decreases as the interparticle bonding force increases. In the ACT-JP method, an ACT-JP value was defined as follows, and evaluation was performed using this value. The abrasion amount of the test piece changes depending on the injection speed, and the ACT-JP value here corresponds only at a fixed angle. That is, when the angle of incidence of the alumina particles on the test piece is smaller than 90 °, wear occurs between the alumina particles and the test piece. In order to evaluate the inter-particle bonding force of the graphite particles that originally make up the graphite material that is the test piece, all of the kinetic energy of the alumina particles is used to cleave the graphite particles that make up the graphite test piece that is the test piece. There must be. Therefore, the angle of incidence (θ) of the alumina particles on the test piece is preferably set to 90 °.
ACT-JP value _{= 1 / M V ··· (1} )
M _V = (1000 · W ₁ ) / (ρ · W ₀ ) (2)
M _V : Wear rate of test piece in steady wear state (mm ³ / g)
ρ: bulk density of test piece graphite base material (g / cm ³ )
W ₀ : Amount (g) of propellant (60 mesh alumina powder) used in the ACT-JP test
W ₁ : wear amount (g) of test piece (graphite substrate) in steady wear state
If the ACT-JP value is smaller than 0.2 g / mm ³ , the graphite particles fall off and mix into the wafer substrate when used as a graphite member for an ion implantation apparatus because the bonding force between the graphite particles is insufficient. It is not preferable because it contaminates the internal parts of the ion implantation apparatus. Therefore, the value measured by ACT-JP method further preferably set to 0.23 g / mm ³ or more, and particularly preferably 0.25 g / mm ³ or more.
[0012]
According to a second aspect of the present invention, there is provided a graphite material for an ion implantation apparatus according to the first aspect, which has a thermal shock coefficient of 50 kW / m or more. The present inventors have found that depleted or dropped graphite particles are deposited on a graphite part as pyrolytic carbon by an ion beam, and then pyrolyzed from the graphite part again due to a mismatch between the pyrolytic carbon deposit and the coefficient of thermal expansion of the graphite part. It was found that carbon peeled off and generated dust. It was found that the less the graphite parts were consumed, the less the pyrolytic carbon deposits were generated, and the closer the thermal expansion coefficient of the graphite parts and the thermal expansion coefficient of the pyrolytic carbon were, the more the deposited pyrolytic carbon was less likely to peel off. Was. Further, the graphite component irradiated with the ion beam is heated to a high temperature instantaneously, so that it is required to have high thermal shock and heat dissipation. The thermal shock coefficient is a general expression of such physical properties. The thermal shock coefficient is represented by (tensile strength x thermal conductivity) / (elastic coefficient x thermal expansion coefficient). By setting the thermal shock coefficient to 50 kW / m or more, it is possible to prevent the pyrolytic carbon fine particles deposited on the surface of the graphite component from falling off and to improve the thermal shock resistance. The thermal shock coefficient is more preferably at least 60 kW / m, particularly preferably at least 70 kW / m.
[0013]
As an example of a method for producing a graphite material for an ion implantation apparatus having an ACT-JP value of 0.2 g / mm ³ or more according to the present invention, there is a petroleum or coal raw or calcined pulverized to several μm to several tens μm. A coke or the like is used as a filler, and a thermosetting resin such as pitch, coal tar, coal tar pitch, phenolic resin, and furan resin is added as a binder and kneaded. In this case, in order to improve the strength of the graphite material, it is preferable to use petroleum-based or coal-based raw coke or mesocarbon microbeads having self-sintering properties as the filler. At least one of these fillers is kneaded with a binder.
[0014]
The kneaded material obtained by the above-mentioned method is pulverized to several μm to several tens μm to obtain a pulverized material. It is preferable that large particles (coarse particles) having a particle size exceeding 100 μm are removed and the particle sizes of the particles are made as uniform as possible. By controlling the maximum particle size of the pulverized powder to several μm to several tens μm, the size of the graphite particles falling off when used as a member for an ion implantation apparatus can be reduced.
[0015]
The above-mentioned pulverized powder is formed, fired and graphitized to obtain a graphite material. Graphitization is usually carried out at 2500 ° C. or higher. In particular, graphitization is carried out at 2800 ° C. or higher to improve the thermal conductivity, thereby reducing the consumption of graphite material by ion beams and improving heat resistance when used as an ion implanter component. The impact property can be improved.
[0016]
After processing this graphite material into the shape of a member for an ion implantation apparatus, a high-purity treatment is performed using a halogen gas or a halogen-containing gas, and the ash content in the graphite member is reduced to 20 ppm or less. Unnecessary impurity elements are not mixed, and the consumption of graphite material can be reduced.
[0017]
In addition, it is more suitable as a graphite material for an ion implantation apparatus by ultrasonically cleaning working powder (powder at the time of cutting) contained in the surface or pores of the graphite member after the purification treatment with pure water. Can be something. It goes without saying that the formation of pyrolytic carbon, glassy carbon or a ceramic coating on the surface or inside of the graphite material according to the present invention can reduce the loss of graphite particles and the consumption of graphite parts.
[0018]
Effect of the Invention
In the present invention, since the particle size is controlled in each of the pulverizing steps, the bonding force between the graphite particles is increased, so that the graphite particles are less likely to fall off. In addition, the above-mentioned method makes it possible to produce a graphite material having a low coefficient of thermal expansion, so that even if exhausted graphite particles are converted into pyrolytic carbon by an ion beam and deposited on a graphite component, they are not separated. As a result, dust generation can be reduced.
[0019]
【Example】
The present invention will be specifically described based on the following examples, but the present invention is not limited to these examples.
[0020]
(Example 1)
Coal pitch coke was pulverized to an average particle size of 3 μm. To 100 parts by weight of the pulverized powder, 100 parts by weight of coal tar pitch was added as a binder and kneaded by a conventional method. The kneaded material was pulverized by a pulverizer so that the maximum particle diameter became 30 μm or less. This pulverized product was formed into a size of 150 × 450 × 1000 (mm) by a cold isostatic pressing method. After firing this molded body at 1000 ° C., it was graphitized at 2500 ° C. The ACT-JP value and the thermal shock coefficient of this graphitized product were measured. Table 1 shows the results. This graphitized product was machined into a graphite member for an ion implantation apparatus, and subjected to high-purification treatment in a halogen-containing gas at 2000 ° C. under reduced pressure to reduce the ash content to 10 ppm or less. The high-purity graphite member for the ion implantation apparatus was further ultrasonically cleaned with pure water. This high-purity graphite member for an ion implantation apparatus was used for implantation of As ions into a silicon wafer.
[0021]
(Example 2)
The coal pitch coke was pulverized to 3 μm. To 100 parts by weight of the pulverized powder, 90 parts by weight of coal tar pitch was added as a binder and kneaded by a conventional method. This kneaded material was pulverized by a pulverizer so that the maximum particle diameter became 50 μm. This pulverized material was formed into a size of 180 × 450 × 1000 (mm) by a cold isostatic pressing method. After firing this molded body at 1000 ° C., pitch impregnation and firing were repeated once each, and then a graphitization treatment was performed at 2500 ° C. The ACT-JP value and the thermal shock coefficient of this graphitized product were measured. Table 1 shows the results. This graphitized product was machined into a graphite member for an ion implantation apparatus, and was subjected to high-purification treatment under reduced pressure at 2000 ° C. in a halogen gas atmosphere to reduce the ash content to 10 ppm or less. The high-purity graphite member for the ion implantation apparatus was further ultrasonically cleaned with pure water. This graphite member for an ion implantation apparatus was used for implantation of As ions into a silicon wafer.
[0022]
(Example 3)
Coal pitch coke was ground to 5 μm. 90 parts by weight of coal tar pitch was added to 100 parts by weight of the pulverized powder and kneaded by a conventional method. This kneaded material was pulverized by a pulverizer so that the maximum particle diameter became 70 μm or less. This pulverized product was formed into the same dimensions as in Example 1 by cold isostatic pressing. After firing this molded body at 1000 ° C., it was graphitized at 2500 ° C. This graphitized product was machined to 100 × 150 × 50 (mm), impregnated with a phenol resin, and fired at 1500 ° C. The ACT-JP value and the thermal shock coefficient of this phenol resin impregnated and fired product were measured. Table 1 shows the results. After the phenol resin impregnated and fired product was machined, it was subjected to high-purification treatment under reduced pressure at 2000 ° C. in a halogen gas atmosphere to obtain a high-purity graphite member for an ion implantation apparatus in which the ash content was reduced to 10 ppm or less. This high-purity graphite member for an ion implanter was further subjected to ultrasonic cleaning with pure water, and then incorporated into an ion implanter to be used for implanting As ions into a silicon wafer.
[0023]
(Comparative Example 1)
Coal pitch coke was pulverized to an average particle size of 8 μm. To 100 parts by weight of this pulverized powder, 80 parts by weight of coal tar pitch was added as a binder and kneaded by a conventional method. This kneaded material was pulverized by a pulverizer so that the maximum particle diameter became 50 μm or less. This pulverized product was formed into a size of 120 × 400 × 800 (mm) by a cold isostatic pressing method. After firing this molded body at 1000 ° C., it was graphitized at 2500 ° C. The ACT-JP value and the thermal shock coefficient of this graphitized product were measured. Table 1 shows the results. This graphitized product is machined into a graphite member for ion implantation, and subjected to high-purification treatment under reduced pressure at 2000 ° C. in a halogen gas atmosphere to reduce the ash content to 10 ppm or less. A graphite member was obtained. The high-purity graphite member for the ion implantation apparatus was further ultrasonically cleaned with pure water. This high-purity graphite member for an ion implantation apparatus was used for implantation of As ions into a silicon wafer.
[0024]
(Comparative Example 2)
Coal pitch coke was pulverized to an average particle diameter of 10 μm. To 100 parts by weight of this pulverized powder, 70 parts by weight of coal tar pitch was added as a binder and kneaded by a conventional method. This kneaded material was secondarily pulverized by a pulverizer so that the maximum particle diameter became 150 μm or less. This pulverized product was formed into a size of 230 × 540 × 1000 (mm) by cold isostatic pressing. After firing this molded body at 1000 ° C., pitch impregnation and firing were repeated once each, and then a graphitization treatment was performed at 3000 ° C. The ACT-JP value and the thermal shock coefficient of this graphitized product were measured. Table 1 shows the results. This graphitized product was machined to obtain a graphite member for an ion implantation apparatus, and subjected to high-purification treatment under reduced pressure at 2000 ° C. in a halogen gas atmosphere to reduce the ash content to 10 ppm or less. The high-purity graphite member for the ion implantation apparatus was further ultrasonically cleaned with pure water. This high-purity graphite member for an ion implantation apparatus was used for implantation of As ions into a silicon wafer.
[0025]
When the high-purity graphite members according to Examples 1 to 3 and Comparative Examples 1 and 2 were used, the size of the dropped graphite particles and the dust generation in the ion implantation apparatus were measured. Table 1 also shows the results.
[0026]
[Table 1]

[0027]
In Table 1, the thermal shock coefficient (kW / m) is the tensile strength (MPa), the thermal conductivity (W / m · K), the coefficient of thermal expansion from room temperature to 400 ° C. (× 10 ⁻⁶ / ° C.), and the elasticity. It was calculated from the coefficient (GPa).
The thermal conductivity was measured by a laser flash method (thermal diffusivity thermal constant measuring device (manufactured by Vacuum Riko Co., Ltd.)), and calculated from the measured value and the specific heat at room temperature of 0.695 J / g · K. .
The coefficient of thermal expansion (× 10 ⁻⁶ / ° C.) was obtained from a room temperature to 400 ° C. using a thermomechanical analyzer (TMA8310) manufactured by Rigaku Corporation.
The modulus of elasticity (GPa) was determined according to Japanese Industrial Standards (JIS) R-7222-1997.
The elastic modulus (GPa) was determined according to JIS R7202-1979.
The size of the dropped graphite particles was determined by observation with a scanning electron microscope.
The dusting property in the ion implantation apparatus was measured by a particle counter, and was evaluated as x, △, 、, or 順 に in descending order of the number of graphite particles.
[0028]
Table 1 shows that the graphite material according to the present invention consumes less graphite particles and has a smaller graphite particle diameter as compared with the graphite material of the comparative example. Moreover, it can be seen that the generation of dust in the ion implantation apparatus due to the graphite particles dropped from the graphite member is small.
[0029]
【The invention's effect】
In the present invention, since the particle diameter in each pulverization step is controlled, a graphite material having a strong bonding force between graphite particles can be obtained. As a result, the consumption of the graphite member is small, and the diameter of the graphite particles falling off can be reduced. Therefore, dust generation inside the wafer substrate or the ion implantation apparatus can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an ion implantation apparatus.
FIG. 2 is a schematic diagram showing an ACT-JP method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Control microcomputer 2 Wafer mounting 3 Cassette 4 Separation power supply 5 Separation electromagnet 6 Acceleration electrode 7 Shutter 8 Silicon wafer substrate 9 Beam stop 10 Deflection electrode 11 Leader electrode 12 Ammeter 13 Ion source 14 High voltage power supply 15 Vacuum pump 21 Graphite material test piece 22 Injection nozzle

Claims (3)

A graphite material for an ion implantation apparatus whose measured value by the ACT-JP method is 0.2 g / mm ³ or more. The graphite material for an ion implantation apparatus according to claim 1, wherein the graphite material has a thermal shock coefficient of 50 kW / m or more. A graphite member for an ion implantation apparatus using the graphite material according to claim 1.

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