JP2659876B2 - Impurity analysis method for high purity graphite used in semiconductor manufacturing process - Google Patents
Impurity analysis method for high purity graphite used in semiconductor manufacturing processInfo
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- JP2659876B2 JP2659876B2 JP3337575A JP33757591A JP2659876B2 JP 2659876 B2 JP2659876 B2 JP 2659876B2 JP 3337575 A JP3337575 A JP 3337575A JP 33757591 A JP33757591 A JP 33757591A JP 2659876 B2 JP2659876 B2 JP 2659876B2
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- graphite
- manufacturing process
- nitric acid
- semiconductor manufacturing
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、黒鉛を利用するような
半導体製造工程での不純物管理に有効に用いられる半導
体製造工程に使用される高純度黒鉛中の不純物分析方法
の改良に関する。The present invention relates to a semiconductor to be effectively used in the impurities management in the semiconductor manufacturing process, such as utilizing a graphite
The present invention relates to an improvement in a method for analyzing impurities in high-purity graphite used in a body manufacturing process .
【０００２】[0002]
【従来の技術】従来、黒鉛を利用するような半導体製造
工程、例えばチョクラルスキー法による結晶製造や、エ
ピタキシャル薄膜製造工程における不純物の混入を防ぐ
ことは重要である。なぜならば、このような工程で作ら
れる製品は半導体素子の基板として使用されるが、この
基板のなかに鉄（Ｆｅ）、ナトリウム（Ｎａ）、銅（Ｃ
ｕ）などの不純物が存在すると、たとえその量が極微量
であったとしても素子の電気特性に影響を与えるからで
ある。2. Description of the Related Art Conventionally, it is important to prevent impurities from being mixed in a semiconductor manufacturing process using graphite, for example, a crystal manufacturing process by the Czochralski method or an epitaxial thin film manufacturing process. This is because a product manufactured in such a process is used as a substrate of a semiconductor device, and iron (Fe), sodium (Na), copper (C)
This is because the presence of impurities such as u) affects the electrical characteristics of the device even if the amount is very small.
【０００３】このような不純物の混入を防ぐ不純物管理
を行う前提として、まず黒鉛中の不純物分析を行うこと
が不可欠である。[0003] As a precondition for performing impurity management to prevent such contamination of impurities, it is essential to first analyze impurities in graphite.
【０００４】黒鉛中の不純物を分析するために初期の段
階では発光分析が用いられていた。しかし、この方法で
は検出限界が高いため半導体製造工程に使用するような
高純度黒鉛中の不純物分析は不可能であった。このた
め、溶液分析が必要となってきた。この場合の前処理方
法としては、乾式灰化法が用いられてきた。[0004] In the early stages, emission analysis was used to analyze impurities in graphite. However, this method has a high detection limit, so that it is impossible to analyze impurities in high-purity graphite used in a semiconductor manufacturing process. For this reason, solution analysis has become necessary. As a pretreatment method in this case, a dry ashing method has been used.
【０００５】乾式灰化法は次のような手順で行われる。
即ち、サンプリング→灰化→溶解→蒸発乾固→再溶解→
分析である。この時の灰化は、酸素雰囲気中１０００℃
程度で行われる。また、溶解は硝酸及び弗酸の混合液が
用いられる。[0005] The dry ashing method is performed in the following procedure.
That is, sampling → incineration → dissolution → evaporation to dryness → re-dissolution →
It is an analysis. Ashing at this time is performed at 1000 ° C. in an oxygen atmosphere.
Done in the degree. For the dissolution, a mixed solution of nitric acid and hydrofluoric acid is used.
【０００６】[0006]
【発明が解決しようとする課題】しかしながら、この乾
式灰化法では１０００℃という高温が必要なため不純物
元素の揮発及び処理中の汚染の恐れがある。また、分析
までに５工程が必要なため時間を要するという問題があ
った。However, in this dry incineration method, a high temperature of 1000 ° C. is required, and there is a risk of volatilization of impurity elements and contamination during processing. In addition, there is a problem that time is required because five steps are required until analysis.
【０００７】本発明は、上記した従来技術に鑑みてなさ
れたもので、工程の簡略化ができるとともに２００℃程
度の低温で分析ができ、短時間で正確な分析を可能と
し、有用性の極めて大きい半導体製造工程に使用される
高純度黒鉛中の不純物分析方法を提供することを目的と
する。[0007] The present invention has been made in view of the above-mentioned conventional technology, and it is possible to simplify the process and perform analysis at a low temperature of about 200 ° C, thereby enabling accurate analysis in a short time.
And it is used to a very large semiconductor manufacturing process usefulness
An object of the present invention is to provide a method for analyzing impurities in high-purity graphite.
【０００８】[0008]
【課題を解決するための手段】上記課題を解決するため
に、本発明においては、粒径１ｍｍ以下の微粒状とした
黒鉛試料に、硫酸と硝酸と過酸化水素からなる混酸を加
え、マイクロウェーブを照射して該黒鉛試料を分解し、
分析に供する方法であり、上記混酸における硫酸：硝酸
と過酸化水素の混合割合が１０：１〜１：１０、硝酸：
過酸化水素の配合比率が１：９９〜９９：１であるよう
にしたものである。In order to solve the above problems, in the present invention, a mixed acid comprising sulfuric acid, nitric acid and hydrogen peroxide is added to a fine graphite sample having a particle size of 1 mm or less. In addition, the graphite sample is decomposed by microwave irradiation,
A method of for analysis, sulfate in the mixed acid: nitric acid
And hydrogen peroxide at a mixing ratio of 10: 1 to 1:10, nitric acid:
The mixing ratio of hydrogen peroxide is from 1:99 to 99: 1
It was made .
【０００９】上記黒鉛試料を微粒状とする手段として
は、高純度シリコンのナイフ状加工品を用いるのが不純
物の混入を防ぐ意味から好ましく、具体的にはシリコン
ウェーハをナイフ状に加工したものを用いるのが好まし
い。As a means for forming the graphite sample into fine particles, it is preferable to use a knife-shaped processed product of high-purity silicon from the viewpoint of preventing contamination of impurities. Specifically, a silicon wafer processed into a knife shape is used. It is preferably used.
【００１０】微粒状の黒鉛試料の粒径が１ｍｍを越える
と溶解時間が長くなり好ましくない。また針状の試料の
場合には直径が１ｍｍを越えると同様の理由で好ましく
ない。 [0010] The particle size of the fine-grained graphite sample is more than 1mm
And the dissolution time is undesirably long. In the case of a needle-shaped sample, it is preferable that the diameter exceeds 1 mm for the same reason.
Absent.
【００１１】本発明において、混酸として用いられるも
のは、硫酸と硝酸と過酸化水素とからなるものである。
硫酸に硝酸と過酸化水素を加える態様としては、最初か
ら加えてもよいし、所定時間経過後に硝酸及び過酸化水
素を加えることもできる。In the present invention, the mixture used as the mixed acid is composed of sulfuric acid, nitric acid and hydrogen peroxide.
As a mode of adding nitric acid and hydrogen peroxide to sulfuric acid, nitric acid and hydrogen peroxide may be added from the beginning, or nitric acid and hydrogen peroxide may be added after a predetermined time has elapsed.
【００１２】硫酸：硝酸と過酸化水素の混合割合は１
０：１〜１：１０の範囲である。あまり硫酸が多いと、
分解に時間がかかり、硝酸と過酸化水素が多過ぎると蒸
発の危険性がある。また、硝酸：過酸化水素の配合割合
は、１：９９〜９９：１の範囲である。 Sulfuric acid: The mixing ratio of nitric acid and hydrogen peroxide is 1
The range is from 0: 1 to 1:10 . If there is too much sulfuric acid,
Decomposition takes time and too much nitric acid and hydrogen peroxide risks evaporation. The mixing ratio of nitric acid: hydrogen peroxide is in the range of 1:99 to 99: 1 .
【００１３】マイクロウェーブの照射は、例えば市販の
マイクロウェーブ灰化装置を用いることによって行うこ
とができる。このマイクロウェーブの照射時間は、用い
る混酸の配合割合によっても異なるが、例えば黒鉛試料
０．０２ｇに対しては大体３時間程度照射すれば分解が
できる。The microwave irradiation can be performed, for example, by using a commercially available microwave incinerator. The microwave irradiation time varies depending on the mixing ratio of the mixed acid used. For example, 0.02 g of a graphite sample can be decomposed by irradiation for about 3 hours.
【００１４】この分解した黒鉛試料は、脱イオン水等で
希釈して、公知の分析方法、例えば、ＩＣＰ−ＡＥＳ
（誘導結合プラズマ発光分析）、ＩＣＰ−ＭＳ（誘導結
合プラズマ質量分析）又はフレームレス原子吸光等によ
って分析される。[0014] The decomposed graphite sample is diluted with deionized water or the like and subjected to a known analysis method, for example, ICP-AES.
(Inductively coupled plasma emission spectrometry), ICP-MS (inductively coupled plasma mass spectrometry), flameless atomic absorption, or the like.
【００１５】[0015]
【作用】微粒状の黒鉛試料を加熱しただけでは、分解は
ほとんど生じない。しかし、本発明者は、マイクロウェ
ーブを照射することにより加熱に加え、液の分子振動に
より黒鉛表面への反応物質の供給を高めることができ、
分解を生ずることを見出し本発明を完成したものであ
る。[Effect] Decomposition hardly occurs only by heating a fine graphite sample. However, the present inventors can increase the supply of the reactants to the graphite surface by molecular vibration of the liquid, in addition to heating by irradiating the microwave,
It has been found that decomposition occurs and the present invention has been completed.
【００１６】このとき、黒鉛と酸の接する面積が大きい
ほど反応は早く進むが、このためには、試料の粒径を小
さくすればよいものである。この試料の粒径を小さくす
るには、機械的な切削が最もよいが、用いる治具からの
汚染が生じる可能性がある。これを防ぐために、本発明
においてはシリコン単結晶を用いた治具、例えばシリコ
ンウェーハをナイフ状に加工した物を用いている。シリ
コン単結晶は、非常に高純度であるためシリコン以外の
汚染は生じない。At this time, the reaction proceeds faster as the area of contact between the graphite and the acid increases, but this can be achieved by reducing the particle size of the sample. In order to reduce the particle size of the sample, mechanical cutting is best, but contamination from the jig used may occur. In order to prevent this, in the present invention, a jig using a silicon single crystal, for example, a silicon wafer processed into a knife shape is used. Since the silicon single crystal has a very high purity, contamination other than silicon does not occur.
【００１７】また、本発明において、黒鉛試料の分解に
硫酸を用いるのは沸点が高いために分解中の蒸発が生じ
ないようにするためである。しかし、硫酸だけでは分解
が進行しないため酸化剤を加える必要がある。本発明で
は、この酸化剤の作用を行うものとして硝酸と過酸化水
素を加える。この酸化剤の加え方としては最初から加え
てもよいし、最初は硫酸のみを用い、所定時間経過後に
一定時間おきに小量づつ加えることもできる。In the present invention, sulfuric acid is used to decompose the graphite sample in order to prevent evaporation during decomposition due to its high boiling point. However, since decomposition does not proceed with sulfuric acid alone, it is necessary to add an oxidizing agent. In the present invention, nitric acid and hydrogen peroxide are added to perform the action of the oxidizing agent. The oxidizing agent may be added from the beginning, or only the sulfuric acid may be used initially, and the oxidizing agent may be added in small amounts at predetermined intervals after a predetermined time has elapsed.
【００１８】[0018]
【実施例】以下に本発明を実施例を用いて説明するが、
本発明がこの実施例に限定されるものでないことはいう
までもない。EXAMPLES The present invention will be described below with reference to examples.
It goes without saying that the present invention is not limited to this embodiment.
【００１９】実施例１ ブロック状の黒鉛（等方性圧縮材）を用い、これをグロ
ーブボックスの中でシリコンウェーハをナイフ状に加工
した物を用いて粒径が１ｍｍ以下になるように切削し
た。この粉末状の黒鉛試料をテフロン製のビーカーに入
れた硝酸中に３０分浸漬後脱イオン水で濯ぐ作業を３回
繰り返し、表面を洗浄した。この操作を終えた粉末２０
ｍｇを石英製のビーカーに入れる。Example 1 A block of graphite (isotropically compressed material) was used, which was cut into a glove box using a knife-shaped silicon wafer processed to a grain size of 1 mm or less. . This powdery graphite sample was immersed in nitric acid in a Teflon beaker for 30 minutes and then rinsed with deionized water three times to clean the surface. Powder 20 after this operation
mg in a quartz beaker.
【００２０】これに分析用の高純度硫酸（多摩化学
（株）製、ＡＡ−１０００）４ｍｌと硝酸４ｍｌと過酸
化水素３ｍｌを加えた。このビーカーにマイクロウェー
ブ灰化装置（ＰＲＯＬＡＢＯ社ＭＩＣＲＯＤＩＧＥＳＴ
３００）を用いてマイクロウェーブを約３時間照射し
て、黒鉛試料を完全に溶解させた。このとき、ビーカー
中の溶液の温度は最高１９２℃まで上昇した。To this were added 4 ml of high-purity sulfuric acid for analysis (AA-1000, manufactured by Tama Chemical Co., Ltd.), 4 ml of nitric acid and 3 ml of hydrogen peroxide. This beaker is equipped with a microwave incinerator (MICRODIGEST manufactured by PROLABO).
The graphite sample was completely dissolved by irradiating microwaves for about 3 hours using (300). At this time, the temperature of the solution in the beaker rose to a maximum of 192 ° C.
【００２１】得られた溶液を脱イオン水で２５ｍｌに希
釈し、フレームレス原子吸光によって分析を行った。分
析の結果は次の通りであった。The resulting solution was diluted to 25 ml with deionized water and analyzed by flameless atomic absorption. The results of the analysis were as follows.
【００２２】Ｆｅ：３０．１８ｐｐｍ、Ｃｕ：１．１３
ｐｐｍ、Ｃｒ：検出限界以下、Ｎｉ：検出限界以下、Ｎ
ａ：検出限界以下、Ｚｎ：検出限界以下。Fe: 30.18 ppm, Cu: 1.13
ppm, Cr: below detection limit, Ni: below detection limit, N
a: below the detection limit, Zn: below the detection limit.
【００２３】比較例１ 実施例１と同様の黒鉛試料２０ｍｇに高純度硫酸（多摩
化学（株）製、ＡＡ−１０００）４ｍｌと過酸化水素１
ｍｌを加えた。このビーカーに実施例１と同様にマイク
ロウェーブを照射した。１時間経過毎に過酸化水素を１
ｍｌ加えた。約６時間で黒鉛試料が完全に溶解した。こ
のとき、ビーカー中の溶液の温度は最高１９４℃まで上
昇した。 Comparative Example 1 A 20 mg graphite sample as in Example 1 was mixed with 4 ml of high-purity sulfuric acid (AA-1000, manufactured by Tama Chemical Co., Ltd.) and hydrogen peroxide 1
ml was added. This beaker was irradiated with microwaves as in Example 1. 1 hour of hydrogen peroxide
ml was added. The graphite sample completely dissolved in about 6 hours. At this time, the temperature of the solution in the beaker rose to a maximum of 194 ° C.
【００２４】得られた溶液を脱イオン水で２５ｍｌに希
釈し、フレームレス原子吸光によって分析を行った。分
析の結果は次の通りであった。The resulting solution was diluted to 25 ml with deionized water and analyzed by flameless atomic absorption. The results of the analysis were as follows.
【００２５】Ｆｅ：３０．１６ｐｐｍ、Ｃｕ：１．１２
ｐｐｍ、Ｃｒ：検出限界以下、Ｎｉ：検出限界以下、Ｎ
ａ：検出限界以下、Ｚｎ：検出限界以下。比較例２ 実施例１と同様の黒鉛試料２０ｍｇに高純度硫酸（多摩
化学（株）製、ＡＡ−１０００）４ｍｌと硝酸１ｍｌを
加えた。このビーカーに実施例１と同様にマイクロウェ
ーブを照射した。１時間経過毎に硝酸を１ｍｌ加えた。
約４時間で黒鉛試料が完全に溶解した。このとき、ビー
カー中の溶液の温度は最高１９６℃まで上昇した。Fe: 30.16 ppm, Cu: 1.12
ppm, Cr: below detection limit, Ni: below detection limit, N
a: below the detection limit, Zn: below the detection limit. Comparative Example 2 To 20 mg of the same graphite sample as in Example 1, 4 ml of high-purity sulfuric acid (AA-1000, manufactured by Tama Chemical Co., Ltd.) and 1 ml of nitric acid were added. This beaker was irradiated with microwaves as in Example 1. Every hour, 1 ml of nitric acid was added.
The graphite sample completely dissolved in about 4 hours. At this time, the temperature of the solution in the beaker rose to a maximum of 196 ° C.
【００２６】得られた溶液を脱イオン水で２５ｍｌに希
釈し、フレームレス原子吸光によって分析を行った。分
析の結果は次の通りであった。The resulting solution was diluted to 25 ml with deionized water and analyzed by flameless atomic absorption. The results of the analysis were as follows.
【００２７】Ｆｅ：３０．１７ｐｐｍ、Ｃｕ：１．１４
ｐｐｍ、Ｃｒ：検出限界以下、Ｎｉ：検出限界以下、Ｎ
ａ：検出限界以下、Ｚｎ：検出限界以下。 比較例３ 実施例１と同様の黒鉛試料２０ｍｇに高純度硫酸（多摩
化学（株）製、ＡＡ−１０００）４ｍｌのみを加えた。
このビーカーに実施例１と同様にマイクロウェーブを６
時間照射した。黒鉛試料は全く溶解しなかった。 比較例４ シリコンウェーハをナイフ状に加工したものの代わりに
金属性ナイフを用いてブロック状の黒鉛を切削した以外
は、実施例１と同様にして黒鉛試料を溶解し、不純物の
分析を行った。分析の結果は次の通りであった。Fe: 30.17 ppm, Cu: 1.14
ppm, Cr: below detection limit, Ni: below detection limit, N
a: below the detection limit, Zn: below the detection limit. Comparative Example 3 To 20 mg of the same graphite sample as in Example 1, only 4 ml of high-purity sulfuric acid (AA-1000, manufactured by Tama Chemical Co., Ltd.) was added.
The microwave was applied to this beaker in the same manner as in Example 1.
Irradiated for hours. The graphite sample did not dissolve at all. Comparative Example 4 A graphite sample was dissolved and analyzed for impurities in the same manner as in Example 1 except that a block-like graphite was cut using a metal knife instead of a silicon wafer processed into a knife shape. The results of the analysis were as follows.
【００２８】Ｆｅ：２２４．００ｐｐｍ、Ｃｕ：３０．
３０ｐｐｍ、Ｃｒ：３．２８ｐｐｍ、Ｎｉ：３９１．０
０ｐｐｍ、Ｎａ：１８８．３０ｐｐｍ、Ｚｎ：６７．０
０ｐｐｍ。Fe: 224.00 ppm, Cu: 30.
30 ppm, Cr: 3.28 ppm, Ni: 391.0
0 ppm, Na: 188.30 ppm, Zn: 67.0
0 ppm.
【００２９】[0029]
【発明の効果】以上のべたごとく、本発明によれば、サ
ンプリング→分解→分析という３工程で分析が可能とな
り、工程の簡略化を達成するとともに２００℃程度の低
温で半導体製造工程に使用される高純度黒鉛中の不純物
の分析ができ、短時間で正確な分析が可能となり、有用
性の極めて大きいものである。As described above, according to the present invention, analysis can be performed in three steps of sampling, disassembly, and analysis, thereby achieving simplification of the steps and use in a semiconductor manufacturing process at a low temperature of about 200 ° C. that can analyze impurities in high purity graphite, short time enables accurate analysis becomes, is extremely high usefulness.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 岩崎 淳 福井県武生市北府２丁目13番50号 信越 半導体株式会社 武生工場内 (72)発明者 木暮 克之 群馬県安中市磯部２丁目13番１号 信越 半導体株式会社 半導体磯部研究所内 (56)参考文献 特開 昭57−14736（ＪＰ，Ａ) ──────────────────────────────────────────────────続 き Continuing from the front page (72) Atsushi Iwasaki, Inventor 2- 13-50 Kitafu, Takefu-shi, Fukui Prefecture Inside the Takefu Plant of Shin-Etsu Semiconductor Co., Ltd. (72) Inventor Katsuyuki Kogure 2-3-1 Isobe, Annaka-shi, Gunma Prefecture No. Shin-Etsu Semiconductor Co., Ltd. Semiconductor Isobe Laboratory (56) References JP-A-57-14736 (JP, A)
Claims (2)
に、硫酸と硝酸と過酸化水素からなる混酸を加え、マイ
クロウェーブを照射して該黒鉛試料を分解し、分析に供
する方法であり、上記混酸における硫酸：硝酸と過酸化
水素の混合割合が１０：１〜１：１０、硝酸：過酸化水
素の配合比率が１：９９〜９９：１であるようにしたこ
とを特徴とする半導体製造工程に使用される高純度黒鉛
中の不純物分析方法。1. A mixed acid comprising sulfuric acid, nitric acid and hydrogen peroxide is added to a finely divided graphite sample having a particle size of 1 mm or less, and the sample is decomposed by microwave irradiation to be analyzed.
Sulfuric acid: nitric acid and peroxide in the above mixed acids
Hydrogen mixture ratio: 10: 1 to 1:10, nitric acid: peroxide water
A method for analyzing impurities in high-purity graphite used in a semiconductor manufacturing process, wherein a compounding ratio of element is 1:99 to 99: 1 .
状加工品を用いて微粒状とすることを特徴とする請求項
１記載の半導体製造工程に使用される高純度黒鉛中の不
純物分析方法。2. The method for analyzing impurities in high-purity graphite used in a semiconductor manufacturing process according to claim 1, wherein said graphite sample is made into fine particles using a knife-like processed product of high-purity silicon.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3337575A JP2659876B2 (en) | 1991-11-27 | 1991-11-27 | Impurity analysis method for high purity graphite used in semiconductor manufacturing process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3337575A JP2659876B2 (en) | 1991-11-27 | 1991-11-27 | Impurity analysis method for high purity graphite used in semiconductor manufacturing process |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05149847A JPH05149847A (en) | 1993-06-15 |
| JP2659876B2 true JP2659876B2 (en) | 1997-09-30 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3337575A Expired - Lifetime JP2659876B2 (en) | 1991-11-27 | 1991-11-27 | Impurity analysis method for high purity graphite used in semiconductor manufacturing process |
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| JP (1) | JP2659876B2 (en) |
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| JP4559932B2 (en) * | 2005-08-17 | 2010-10-13 | 株式会社トクヤマ | Method for analyzing metal impurities |
| CN102175557B (en) * | 2011-03-09 | 2012-09-19 | 湖北鄂信钻石材料有限责任公司 | Method for testing trace impurities in ultrahigh-purity graphite |
| JP6436735B2 (en) * | 2013-11-15 | 2018-12-12 | 株式会社住化分析センター | Sample preparation method, analysis method, and quality control method |
| JP6351961B2 (en) * | 2013-12-02 | 2018-07-04 | 御国色素株式会社 | Method for detecting iron content, carbon material-containing slurry controlled by the detection method, and method for producing lithium ion battery |
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| JPS5714736A (en) * | 1980-06-30 | 1982-01-26 | Mitsubishi Chem Ind Ltd | Rapid, wet-type sample decomposing device |
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| JPH05149847A (en) | 1993-06-15 |
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