JP6919625B2 - Impurity concentration measurement method - Google Patents
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Description
本発明は、不純物濃度の測定方法に関し、特にＦＴ−ＩＲ法によりシリコン単結晶中の不純物濃度を測定する方法に関する。 The present invention relates to a method for measuring an impurity concentration, and more particularly to a method for measuring an impurity concentration in a silicon single crystal by the FT-IR method.
炭素や酸素の絶対濃度を測定する方法として、ＰＬ法やＳＩＭＳ法が挙げられる。しかしＰＬ法は、特許文献１にあるように、ＰＬ測定前に電子線照射を必要とするため、迅速に測定することが出来ず、特に製品の出荷検査としては適さない。ＳＩＭＳ法も同様に、測定に時間が掛かるため製品の出荷検査としては適さない。 Examples of the method for measuring the absolute concentration of carbon and oxygen include the PL method and the SIMS method. However, as described in Patent Document 1, the PL method requires electron beam irradiation before PL measurement, so that it cannot be measured quickly, and is not particularly suitable for shipping inspection of products. Similarly, the SIMS method is not suitable for shipping inspection of products because it takes a long time to measure.
一方、炭素や酸素の濃度を簡便に、かつ迅速に測定する方法としてＦＴ−ＩＲ法が挙げられる。ＦＴ−ＩＲ法による炭素濃度の測定方法は、測定サンプルの吸光度スペクトルから、カーボンフリーのリファレンスの吸光度スペクトルを引き（これにより、差スペクトルが得られる）、差スペクトルの６０５ｃｍ−１のＣｓピーク強度を炭素濃度に換算する、というものである。特に特許文献２では、差スペクトルを求める際の差係数を求める方法が、また特許文献３では、Ｃｓピーク強度を求める際に差スペクトルにベースラインを引きやすいように、リファレンスの酸素濃度を測定サンプルより低濃度にすることが開示されている。また、ＦＴ−ＩＲ法による酸素濃度の測定方法は、炭素の場合と同様に差スペクトルを求め、１１０７ｃｍ−１もしくは５１５ｃｍ−１のＯｉピーク強度を酸素濃度に換算する、という方法である。 On the other hand, an FT-IR method can be mentioned as a method for measuring the concentration of carbon and oxygen easily and quickly. In the method of measuring the carbon concentration by the FT-IR method, the absorbance spectrum of the carbon-free reference is subtracted from the absorbance spectrum of the measurement sample (the difference spectrum is obtained), and the Cs peak intensity of 605 cm -1 of the difference spectrum is obtained. It is converted to carbon concentration. In particular, in Patent Document 2, the method of obtaining the difference coefficient when obtaining the difference spectrum is used, and in Patent Document 3, the oxygen concentration of the reference is measured so that the difference spectrum can be easily baselined when obtaining the Cs peak intensity. It is disclosed that the concentration is lower. Further, the method for measuring the oxygen concentration by the FT-IR method is a method in which the difference spectrum is obtained in the same manner as in the case of carbon, and the Oi peak intensity of 1107 cm -1 or 515 cm -1 is converted into the oxygen concentration.
しかしこのような従来の方法で求められる炭素濃度または酸素濃度は、リファレンスに含まれる炭素濃度または酸素濃度との差濃度でしかない。測定サンプル中の炭素濃度または酸素濃度と、炭素または酸素フリーと考えているリファレンスに含まれる炭素濃度または酸素濃度に十分な濃度差がある従来はこの方法で良かったが、製品（測定サンプル）の不純物濃度が減少している現在では、差濃度と絶対濃度の乖離が大きくなってきている。 However, the carbon concentration or oxygen concentration obtained by such a conventional method is only the difference concentration from the carbon concentration or oxygen concentration contained in the reference. There is a sufficient difference between the carbon concentration or oxygen concentration in the measurement sample and the carbon concentration or oxygen concentration contained in the reference that is considered to be carbon or oxygen-free. Now that the impurity concentration is decreasing, the difference between the difference concentration and the absolute concentration is increasing.
上述したように、ＦＴ−ＩＲ法による不純物濃度はリファレンスとの差濃度であるため、絶対濃度が不明であった。特に、製品の不純物濃度が減少している現在では、差濃度と絶対濃度の乖離が大きくなってきており、絶対濃度を求められなくなりつつある。 As described above, since the impurity concentration by the FT-IR method is the difference concentration from the reference, the absolute concentration was unknown. In particular, now that the impurity concentration of products is decreasing, the difference between the difference concentration and the absolute concentration is increasing, and the absolute concentration is no longer required.
本発明は、上記問題点に鑑みてなされたものであって、シリコン単結晶中の不純物の絶対濃度を迅速かつ簡便に測定することができる不純物濃度の測定方法を提供することを目的とする。 The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for measuring an impurity concentration, which can quickly and easily measure the absolute concentration of impurities in a silicon single crystal.
上記目的を達成するために、本発明は、ＦＴ−ＩＲ法によりシリコン単結晶中の不純物濃度を求める不純物濃度の測定方法であって、ＦＴ−ＩＲ法により不純物濃度を求めるに際し、あらかじめ不純物濃度が求められている試料をリファレンスとし、測定サンプルと前記リファレンスとの差スペクトルから前記測定サンプルと前記リファレンスの不純物の差濃度を求め、これに前記リファレンスの不純物濃度を足すことで、前記測定サンプルに含まれる不純物の絶対濃度を求めることを特徴とする不純物濃度の測定方法を提供する。 In order to achieve the above object, the present invention is a method for measuring the impurity concentration in a silicon single crystal by the FT-IR method, and when the impurity concentration is obtained by the FT-IR method, the impurity concentration is determined in advance. Using the obtained sample as a reference, the difference concentration of impurities between the measurement sample and the reference is obtained from the difference spectrum between the measurement sample and the reference, and the impurity concentration of the reference is added to this to be included in the measurement sample. Provided is a method for measuring an impurity concentration, which comprises obtaining the absolute concentration of an impurity.
このように、あらかじめリファレンスに含まれる不純物濃度を測定しておけば、測定サンプルに含まれる不純物の絶対濃度は、リファレンスに含まれる不純物濃度と、ＦＴ−ＩＲ法により求められる不純物の差濃度との和で求めることが出来る。これにより、シリコン単結晶中の不純物の絶対濃度を迅速かつ簡便に測定することができる。 In this way, if the concentration of impurities contained in the reference is measured in advance, the absolute concentration of impurities contained in the measurement sample is the difference concentration between the concentration of impurities contained in the reference and the concentration of impurities obtained by the FT-IR method. It can be calculated in Japanese. Thereby, the absolute concentration of impurities in the silicon single crystal can be measured quickly and easily.
このとき、前記不純物は、炭素または酸素とすることができる。 At this time, the impurity can be carbon or oxygen.
炭素も酸素も、リファレンスの濃度はＰＬ法やＳＩＭＳ法で求めることが出来、また差濃度はＦＴ−ＩＲ法で求めることが出来るため、不純物が炭素または酸素である場合に、本発明を好適に適用できる。 For both carbon and oxygen, the reference concentration can be determined by the PL method or SIMS method, and the difference concentration can be determined by the FT-IR method. Therefore, the present invention is preferably used when the impurity is carbon or oxygen. Applicable.
このとき、前記リファレンスの不純物濃度を、ＰＬ法により求めることが好ましい。 At this time, it is preferable to determine the impurity concentration of the reference by the PL method.
ＰＬ法であれば、精度良くリファレンスの不純物濃度を測定することが出来る。 With the PL method, the impurity concentration of the reference can be measured with high accuracy.
前記不純物が炭素の場合、粒子線を照射した検量線用サンプルをＰＬ測定して得られるＧ線強度、Ｃ線強度、および別に求めた炭素濃度、酸素濃度を用いて、炭素濃度＝比例定数×酸素濃度×（Ｇ線強度／Ｃ線強度）となる比例定数をあらかじめ求めておき、前記リファレンスに前記ＰＬ測定と同条件で粒子線を照射し、前記ＰＬ測定と同条件でＰＬ測定して得られるＧ線強度、Ｃ線強度、および別に求めた酸素濃度を前記関係式に代入することで前記リファレンスの炭素濃度を求めることができる。 When the impurity is carbon, carbon concentration = proportional constant × using the G-ray intensity and C-ray intensity obtained by PL measurement of a calibration curve sample irradiated with particle beams, and the carbon concentration and oxygen concentration obtained separately. Obtain a proportionality constant of oxygen concentration x (G-ray intensity / C-ray intensity) in advance, irradiate the reference with particle beams under the same conditions as the PL measurement, and perform PL measurement under the same conditions as the PL measurement. The carbon concentration of the reference can be obtained by substituting the G-ray intensity, the C-line intensity, and the oxygen concentration obtained separately into the relational expression.
このような方法に依れば、ＰＬ法による炭素濃度測定における酸素濃度の影響を受けずに、リファレンスの正確な炭素濃度を測定することが出来る。 According to such a method, the accurate carbon concentration of the reference can be measured without being affected by the oxygen concentration in the carbon concentration measurement by the PL method.
前記不純物が酸素の場合、粒子線を照射した検量線用サンプルをＰＬ測定して得られるＧ線強度、Ｃ線強度、および別に求めた炭素濃度、酸素濃度を用いて、酸素濃度＝比例定数×炭素濃度×（Ｃ線強度／Ｇ線強度）となる比例定数をあらかじめ求めておき、前記リファレンスに前記ＰＬ測定と同条件で粒子線を照射し、前記ＰＬ測定と同条件でＰＬ測定して得られるＧ線強度、Ｃ線強度、および別に求めた炭素濃度を前記関係式に代入することで前記リファレンスの酸素濃度を求めることができる。 When the impurity is oxygen, oxygen concentration = proportional constant × using the G-ray intensity and C-ray intensity obtained by PL measurement of a calibration curve sample irradiated with particle beams, and the carbon concentration and oxygen concentration obtained separately. Obtain a proportionality constant of carbon concentration × (C-ray intensity / G-ray intensity) in advance, irradiate the reference with particle beams under the same conditions as the PL measurement, and perform PL measurement under the same conditions as the PL measurement. The oxygen concentration of the reference can be obtained by substituting the G-ray intensity, the C-line intensity, and the separately obtained carbon concentration into the relational expression.
このような方法に依れば、ＳＩＭＳ法やＦＴ−ＩＲ法では測定することの出来ない低酸素濃度の定量も可能である。 According to such a method, it is possible to quantify a low oxygen concentration that cannot be measured by the SIMS method or the FT-IR method.
以上のように、本発明の不純物濃度の測定方法によれば、シリコン単結晶中の不純物の絶対濃度を迅速かつ簡便に測定することができる。 As described above, according to the method for measuring the impurity concentration of the present invention, the absolute concentration of impurities in the silicon single crystal can be measured quickly and easily.
以下、本発明について、実施態様の一例として、図を参照しながら詳細に説明するが、本発明はこれに限定されるものではない。 Hereinafter, the present invention will be described in detail with reference to the drawings as an example of an embodiment, but the present invention is not limited thereto.
以下、本発明の不純物濃度の測定方法について、図１を参照しながら説明する。
図１は、本発明の不純物濃度の測定方法を示すフロー図である。
Hereinafter, the method for measuring the impurity concentration of the present invention will be described with reference to FIG.
FIG. 1 is a flow chart showing a method for measuring an impurity concentration of the present invention.
初めに、あらかじめ不純物濃度が求められている試料をリファレンスとする（図１のＳ１１参照）。
リファレンスの不純物濃度は、例えば、ＰＬ法で測定することができる。
First, a sample whose impurity concentration has been determined in advance is used as a reference (see S11 in FIG. 1).
The impurity concentration of the reference can be measured by, for example, the PL method.
不純物が炭素の場合は以下のようにして測定すれば、精度良く絶対濃度を測定できる。
まず、粒子線を照射した検量線用サンプルをＰＬ測定して得られるＧ線強度、Ｃ線強度、および別に求めた炭素濃度、酸素濃度を用いて、
炭素濃度［ａｔｏｍｓ／ｃｍ３］＝比例定数×酸素濃度［ｐｐｍａ−ＪＥＩＴＡ］×（Ｇ線強度／Ｃ線強度）・・・（１）
となる比例定数をあらかじめ求めておく。
具体的には、炭素濃度、および酸素濃度が異なるシリコン単結晶基板（検量線用サンプル）を１５水準用意する。このとき、導出される比例定数の精度を上げる為、５水準以上用意することが好ましい。そして、これらのサンプルの炭素濃度、および酸素濃度をＳＩＭＳ法で測定する。その後、電子線照射装置により各シリコン単結晶基板に２ＭＶの加速電圧で１．０×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２の電子線を照射し、シリコン単結晶基板にＧ線、およびＣ線を生成させ、それらのピーク強度をＰＬ法で測定する。なお、このときのサンプル温度は液体ヘリウム温度とする。これらシリコン単結晶基板において、得られた炭素濃度、酸素濃度、Ｇ線強度、およびＣ線強度を上記の関係式（１）に代入し、得られた比例定数の平均値を比例定数とする。このようにして、比例定数として４．４５×１０１４が得られた。
次に、リファレンスに上記ＰＬ測定と同条件で粒子線を照射し、上記ＰＬ測定と同条件でＰＬ測定して得られるＧ線強度、Ｃ線強度、および別に求めた酸素濃度を上記関係式（１）に代入することでリファレンスの炭素濃度を求めることができる。このとき、リファレンスの酸素濃度は、例えばＳＩＭＳ法により測定することができる。
When the impurity is carbon, the absolute concentration can be measured accurately by measuring as follows.
First, using the G-ray intensity and C-line intensity obtained by PL measurement of the calibration curve sample irradiated with the particle beam, and the carbon concentration and oxygen concentration obtained separately,
Carbon concentration [atoms / cm 3 ] = proportionality constant x oxygen concentration [ppma-JEITA] x (G-line intensity / C-line intensity) ... (1)
The proportionality constant that becomes is obtained in advance.
Specifically, 15 levels of silicon single crystal substrates (calibration curve samples) having different carbon concentrations and oxygen concentrations are prepared. At this time, in order to improve the accuracy of the derived proportionality constant, it is preferable to prepare 5 levels or more. Then, the carbon concentration and the oxygen concentration of these samples are measured by the SIMS method. After that, each silicon single crystal substrate was irradiated with an electron beam of 1.0 × 10 15 electrons / cm 2 at an acceleration voltage of 2 MV by an electron beam irradiator to generate G-rays and C-rays on the silicon single crystal substrate. Their peak intensities are measured by the PL method. The sample temperature at this time is the liquid helium temperature. In these silicon single crystal substrates, the obtained carbon concentration, oxygen concentration, G-ray intensity, and C-line intensity are substituted into the above relational expression (1), and the average value of the obtained proportionality constants is used as the proportionality constant. In this way, 4.45 × 10 14 was obtained as the proportionality constant.
Next, the reference is irradiated with a particle beam under the same conditions as the PL measurement, and the G-ray intensity, the C-ray intensity obtained by the PL measurement under the same conditions as the PL measurement, and the oxygen concentration obtained separately are calculated by the above relational expression (the above relational expression. The carbon concentration of the reference can be obtained by substituting into 1). At this time, the oxygen concentration of the reference can be measured by, for example, the SIMS method.
不純物が酸素の場合は以下のようにして測定すれば、精度良く絶対濃度を測定できる。
まず、粒子線を照射した検量線用サンプルをＰＬ測定して得られるＧ線強度、Ｃ線強度、および別に求めた炭素濃度、酸素濃度を用いて、
酸素濃度［ｐｐｍａ−ＪＥＩＴＡ］＝比例定数×炭素濃度［ａｔｏｍｓ／ｃｍ３］×（Ｃ線強度／Ｇ線強度）・・・（２）
となる比例定数をあらかじめ求めておく。
具体的には、炭素濃度、および酸素濃度が異なるシリコン単結晶基板（検量線用サンプル）を１５水準用意する。そして、これらのサンプルの炭素濃度および酸素濃度をＳＩＭＳ法で測定する。その後、電子線照射装置により各シリコン単結晶基板に２ＭＶの加速電圧で１．０×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２の電子線を照射し、シリコン単結晶基板にＧ線、およびＣ線を生成させ、それらのピーク強度をＰＬ法で測定した。なお、このときのサンプル温度は液体ヘリウム温度とする。これらシリコン単結晶基板において、得られた酸素濃度、炭素濃度、Ｇ線強度、およびＣ線強度を上記の関係式（２）に代入し、得られた比例定数の平均値を比例定数とする。このようにして、比例定数として２．２５×１０−１５が得られた。
次に、リファレンスに上記ＰＬ測定と同条件で粒子線を照射し、上記ＰＬ測定と同条件でＰＬ測定して得られるＧ線強度、Ｃ線強度、および別に求めた炭素濃度を上記の関係式（２）に代入することでリファレンスの酸素濃度を求める。このとき、リファレンスの炭素濃度は、例えばＳＩＭＳ法などにより測定することができる。
When the impurity is oxygen, the absolute concentration can be measured accurately by measuring as follows.
First, using the G-ray intensity and C-line intensity obtained by PL measurement of the calibration curve sample irradiated with the particle beam, and the carbon concentration and oxygen concentration obtained separately,
Oxygen concentration [ppma-JEITA] = Proportional constant x Carbon concentration [atoms / cm 3 ] x (C-line intensity / G-line intensity) ... (2)
The proportionality constant that becomes is obtained in advance.
Specifically, 15 levels of silicon single crystal substrates (calibration curve samples) having different carbon concentrations and oxygen concentrations are prepared. Then, the carbon concentration and oxygen concentration of these samples are measured by the SIMS method. After that, each silicon single crystal substrate was irradiated with an electron beam of 1.0 × 10 15 electrons / cm 2 at an acceleration voltage of 2 MV by an electron beam irradiator to generate G-rays and C-rays on the silicon single crystal substrate. Their peak intensities were measured by the PL method. The sample temperature at this time is the liquid helium temperature. In these silicon single crystal substrates, the obtained oxygen concentration, carbon concentration, G-ray intensity, and C-line intensity are substituted into the above relational expression (2), and the average value of the obtained proportionality constants is used as the proportionality constant. In this way, 2.25 × 10 -15 was obtained as the proportionality constant.
Next, the reference is irradiated with a particle beam under the same conditions as the PL measurement, and the G-ray intensity, the C-ray intensity obtained by the PL measurement under the same conditions as the PL measurement, and the separately obtained carbon concentration are calculated by the above relational expression. The oxygen concentration of the reference is obtained by substituting into (2). At this time, the carbon concentration of the reference can be measured by, for example, the SIMS method.
次に、上記リファレンスを用いて、測定サンプルをＦＴ−ＩＲ法で測定し、測定サンプルとリファレンスとの差スペクトルから測定サンプルとリファレンスの不純物の差濃度を求める。（図１のＳ１２参照）。
具体的には、従来の方法に倣えば良く、炭素の場合はＪＥＩＴＡ ＥＭ−３５０３にあるように、差スペクトルにおける６０５ｃｍ−１のＣｓピーク強度を、酸素の場合は差スペクトルにおける１１０７ｃｍ−１もしくは５１５ｃｍ−１のＯｉピーク強度を、それぞれ炭素濃度または酸素濃度に換算して、リファレンスとの差濃度を求める。
Next, using the above reference, the measurement sample is measured by the FT-IR method, and the difference concentration of impurities between the measurement sample and the reference is obtained from the difference spectrum between the measurement sample and the reference. (See S12 in FIG. 1).
Specifically, the conventional method may be followed. In the case of carbon, the Cs peak intensity of 605 cm -1 in the difference spectrum is as shown in JEITA EM-3503, and in the case of oxygen, 1107 cm -1 or 515 cm in the difference spectrum. The Oi peak intensity of -1 is converted into carbon concentration or oxygen concentration, respectively, and the difference concentration from the reference is obtained.
その後、上記リファレンスの不純物濃度と、図１のＳ１２で求めた不純物の差濃度の和を測定サンプルに含まれる不純物の絶対濃度とする（図１のＳ１３参照）。ここで、差スペクトルにおけるＣｓピークもしくはＯｉピークが負の場合（すなわち、凹形状の場合）は、差濃度はマイナスの値としてリファレンスの不純物濃度との和を求める。負のピークということは、測定サンプルに含まれる不純物濃度がリファレンスに含まれる不純物濃度よりも低い、ということを意味しているためである。 Then, the sum of the impurity concentration of the reference and the difference concentration of the impurities obtained in S12 of FIG. 1 is taken as the absolute concentration of the impurities contained in the measurement sample (see S13 of FIG. 1). Here, when the Cs peak or Oi peak in the difference spectrum is negative (that is, in the case of a concave shape), the difference concentration is set to a negative value and the sum with the impurity concentration of the reference is obtained. The negative peak means that the impurity concentration contained in the measurement sample is lower than the impurity concentration contained in the reference.
また本発明は、リファレンスの不純物の絶対濃度に対する差濃度を求め、両者の和を測定サンプルの不純物の絶対濃度とするものであるので、従来のように、リファレンスは無炭素や無酸素に限定されず、自由に選択することが出来る。 Further, in the present invention, the difference concentration with respect to the absolute concentration of impurities in the reference is obtained, and the sum of the two is used as the absolute concentration of impurities in the measurement sample. You can choose freely.
上記で説明した本発明の不純物濃度の測定方法であれば、シリコン単結晶中の不純物の絶対濃度を迅速かつ簡便に測定することができる。 According to the method for measuring the impurity concentration of the present invention described above, the absolute concentration of impurities in a silicon single crystal can be measured quickly and easily.
また、本発明の不純物濃度の測定方法において、不純物は炭素または酸素とすることができる。炭素も酸素も、リファレンスの濃度はＰＬ法やＳＩＭＳ法で求めることができ、また差濃度はＦＴ−ＩＲ法で求めることが出来るため、不純物が炭素または酸素である場合に、本発明を好適に適用できる。 Further, in the method for measuring the impurity concentration of the present invention, the impurity can be carbon or oxygen. For both carbon and oxygen, the reference concentration can be determined by the PL method or SIMS method, and the difference concentration can be determined by the FT-IR method. Therefore, the present invention is preferably used when the impurity is carbon or oxygen. Applicable.
また、本発明の不純物濃度の測定方法において、リファレンスの不純物濃度を、ＰＬ法により求めることが好ましい。ＰＬ法であれば、精度良くリファレンスの不純物濃度を測定することが出来る。 Further, in the method for measuring the impurity concentration of the present invention, it is preferable to determine the impurity concentration of the reference by the PL method. With the PL method, the impurity concentration of the reference can be measured with high accuracy.
以下、実施例及び比較例を示して本発明をより具体的に説明するが、本発明はこれらに限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
（実施例１）
まず、ＦＴ−ＩＲ測定に用いるリファレンスの炭素濃度を求めた。
直径３００ｍｍのＣＺシリコン結晶から、厚さ２ｍｍの両面研磨サンプルを用意した。初めにＳＩＭＳ法により酸素濃度を測定し、１２．４ｐｐｍａ−ＪＥＩＴＡと求まった。次にこれを２分割し、一方には電子線を照射し、上記に記載した方法で炭素濃度を求めた。即ち、加速電圧２ＭＶ、照射量１．０×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２で電子線を照射し、液体ヘリウム温度でＰＬ測定したところ、Ｇ線強度＝４８５（ａ．ｕ．）、Ｃ線強度＝５３４７７（ａ．ｕ．）と求まった。これらを上記の関係式（１）（比例定数は４．４５×１０１４）に代入することで、このサンプルの炭素濃度は５．０×１０１３ａｔｏｍｓ／ｃｍ３と求まった。そこで、電子線を照射しなかった残りのサンプルをＦＴ−ＩＲ測定のリファレンスとした。
(Example 1)
First, the carbon concentration of the reference used for the FT-IR measurement was determined.
A double-sided polishing sample having a thickness of 2 mm was prepared from a CZ silicon crystal having a diameter of 300 mm. First, the oxygen concentration was measured by the SIMS method, and it was determined to be 12.4 ppma-JEITA. Next, this was divided into two, one of which was irradiated with an electron beam, and the carbon concentration was determined by the method described above. That is, when an electron beam was irradiated at an acceleration voltage of 2 MV and an irradiation amount of 1.0 × 10 15 ejectrons / cm 2 and PL measurement was performed at a liquid helium temperature, G-ray intensity = 485 (au), C-ray intensity =. It was found to be 53477 (au). By substituting these into the above relational expression (1) (proportional constant is 4.45 × 10 14 ), the carbon concentration of this sample was determined to be 5.0 × 10 13 atoms / cm 3 . Therefore, the remaining sample not irradiated with the electron beam was used as a reference for FT-IR measurement.
次に、リファレンスサンプルとは異なる引上条件で引き上げた直径３００ｍｍのＣＺシリコン結晶から、厚さ２ｍｍの両面研磨サンプルを用意した。このサンプルの炭素濃度をＪＥＩＴＡ ＥＭ−３５０３に従ってＦＴ−ＩＲ法で求めたところ、Ｃｓピークは凸形状（すなわち、正の差濃度）で、その差濃度は５．２×１０１４ａｔｏｍｓ／ｃｍ３と求まった。よって、絶対濃度は、リファレンスの濃度と上記で求めた差濃度の和として、５．７×１０１４ａｔｏｍｓ／ｃｍ３と求まった。 Next, a double-sided polishing sample having a thickness of 2 mm was prepared from a CZ silicon crystal having a diameter of 300 mm that was pulled up under different pulling conditions from the reference sample. When the carbon concentration of this sample was determined by the FT-IR method according to JEITA EM-3503, the Cs peak had a convex shape (that is, a positive difference concentration), and the difference concentration was 5.2 × 10 14 infrareds / cm 3 . I was asked. Therefore, the absolute concentration was determined to be 5.7 × 10 14 atoms / cm 3 as the sum of the reference concentration and the difference concentration obtained above.
（実施例２）
実施例１とは別のリファレンス用サンプルを用意し、実施例１と同様の方法でこのサンプルの炭素濃度を求めた。即ち、新たに用意した直径３００ｍｍのＣＺシリコン結晶から切り出した厚さ２ｍｍの両面研磨サンプルの酸素濃度はＳＩＭＳ法により１２．０ｐｐｍａ−ＪＥＩＴＡと求まった。これを２分割し、一方には電子線を照射し、上記に記載した方法で炭素濃度を求めた。即ち、加速電圧２ＭＶ、照射量１．０×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２で電子線を照射し、液体ヘリウム温度でＰＬ測定したところ、Ｇ線強度＝１９９６（ａ．ｕ．）、Ｃ線強度＝６６６２（ａ．ｕ．）と求まった。これらを上記の関係式（１）（比例定数は４．４５×１０１４）に代入することで、このサンプルの炭素濃度は１．６×１０１５ａｔｏｍｓ／ｃｍ３と求まった。そこで、電子線を照射しなかった残りのサンプルをＦＴ−ＩＲ測定のリファレンスとした。
(Example 2)
A reference sample different from that of Example 1 was prepared, and the carbon concentration of this sample was determined by the same method as in Example 1. That is, the oxygen concentration of the 2 mm-thick double-sided polished sample cut out from the newly prepared CZ silicon crystal having a diameter of 300 mm was determined to be 12.0 ppma-JEITA by the SIMS method. This was divided into two, one of which was irradiated with an electron beam, and the carbon concentration was determined by the method described above. That is, when an electron beam was irradiated at an acceleration voltage of 2 MV and an irradiation amount of 1.0 × 10 15 ejectrons / cm 2 and PL measurement was performed at a liquid helium temperature, G-ray intensity = 1996 (au), C-ray intensity =. It was found to be 6662 (a.u.). By substituting these into the above relational expression (1) (proportional constant is 4.45 × 10 14 ), the carbon concentration of this sample was determined to be 1.6 × 10 15 atoms / cm 3 . Therefore, the remaining sample not irradiated with the electron beam was used as a reference for FT-IR measurement.
測定サンプルとしては、実施例１と同じものを用いた。このサンプルの炭素濃度も実施例１と同様にＪＥＩＴＡ ＥＭ−３５０３に従ってＦＴ−ＩＲ法で求めたところ、Ｃｓピークは凹形状（すなわち、負の差濃度）で、差濃度は、−１．０３×１０１５ａｔｏｍｓ／ｃｍ３と求まった。従って、絶対濃度は、リファレンスの濃度と上記で求めた差濃度の和として、５．７×１０１４ａｔｏｍｓ／ｃｍ３と求められ、実施例１の結果と同等であった。 As the measurement sample, the same one as in Example 1 was used. The carbon concentration of this sample was also determined by the FT-IR method according to JEITA EM-3503 in the same manner as in Example 1. The Cs peak had a concave shape (that is, a negative difference concentration), and the difference concentration was −1.03 ×. It was found to be 10 15 atoms / cm 3 . Therefore, the absolute concentration was determined to be 5.7 × 10 14 atoms / cm 3 as the sum of the reference concentration and the difference concentration obtained above, which was equivalent to the result of Example 1.
（実施例３）
まず、ＦＴ−ＩＲ測定に用いるリファレンスの酸素濃度を求めた。
直径２００ｍｍのＦＺシリコン結晶から、厚さ２ｍｍの両面研磨サンプルを用意した。初めにＳＩＭＳ法により炭素濃度を測定し、３．４×１０１４ａｔｏｍｓ／ｃｍ３と求まった。次にこれを２分割し、一方には電子線を照射し、上記に記載した方法で酸素濃度を求めた。即ち、加速電圧２ＭＶ、照射量１．０×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２で電子線を照射し、液体ヘリウム温度でＰＬ測定したところ、Ｇ線強度＝１０６９９（ａ．ｕ．）、Ｃ線強度＝３２１７（ａ．ｕ．）と求まった。これらを上記の関係式（２）（比例定数は２．２５ｘ１０−１５）に代入することで、このサンプルの酸素濃度は０．２３ｐｐｍａ−ＪＥＩＴＡと求まった。そこで、電子線を照射しなかった残りのサンプルをＦＴ−ＩＲ測定のリファレンスとした。
(Example 3)
First, the oxygen concentration of the reference used for the FT-IR measurement was determined.
A double-sided polishing sample having a thickness of 2 mm was prepared from an FZ silicon crystal having a diameter of 200 mm. First, the carbon concentration was measured by the SIMS method, and it was determined to be 3.4 × 10 14 atoms / cm 3 . Next, this was divided into two, one of which was irradiated with an electron beam, and the oxygen concentration was determined by the method described above. That is, when an electron beam was irradiated at an acceleration voltage of 2 MV and an irradiation amount of 1.0 × 10 15 ejectrons / cm 2 and PL measurement was performed at a liquid helium temperature, G-ray intensity = 100099 (au), C-ray intensity =. It was found to be 3217 (a.u.). These above relation (2) (the constant of proportionality 2.25X10 -15) by substituting the oxygen concentration of the sample was Motoma' the 0.23ppma-JEITA. Therefore, the remaining sample not irradiated with the electron beam was used as a reference for FT-IR measurement.
次に、直径３００ｍｍのＣＺシリコン結晶から厚さ２ｍｍの両面研磨サンプルを用意した。このサンプルの酸素濃度を、ＦＴ−ＩＲ測定して得られた差スペクトルにおける１１０７ｃｍ−１（Ｏｉ）ピーク強度から求めたところ、Ｏｉピークは凸形状（すなわち、正の差濃度）で、その差濃度は１２．３０ｐｐｍａと求まった。よって、絶対濃度は、リファレンスの濃度と上記で求めた差濃度の和として、１２．５３ｐｐｍａと求まった。 Next, a double-sided polishing sample having a thickness of 2 mm was prepared from a CZ silicon crystal having a diameter of 300 mm. When the oxygen concentration of this sample was determined from the 1107 cm -1 (Oi) peak intensity in the difference spectrum obtained by FT-IR measurement, the Oi peak had a convex shape (that is, a positive difference concentration), and the difference concentration was obtained. Was found to be 12.30 ppma. Therefore, the absolute concentration was determined to be 12.53 ppma as the sum of the reference concentration and the difference concentration obtained above.
（実施例４）
実施例３とは異なり、リファレンスをＣＺシリコン結晶とし、まずこのリファレンスの酸素濃度を実施例３と同様の方法で求めた。即ち、直径３００ｍｍのＣＺ結晶から、厚さ２ｍｍの両面研磨サンプルを用意した。初めにＳＩＭＳ法により炭素濃度を測定し、４．３×１０１４ａｔｏｍｓ／ｃｍ３と求まった。次にこれを２分割し、一方には電子線を照射し、上記に記載した方法で酸素濃度を求めた。即ち、加速電圧２ＭＶ、照射量１．０×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２で電子線を照射し、液体ヘリウム温度でＰＬ測定したところ、Ｇ線強度＝２２８４（ａ．ｕ．）、Ｃ線強度＝３２３４２（ａ．ｕ．）と求まった。これらを上記の関係式（２）（比例定数は２．２５×１０−１５）に代入することで、このサンプルの酸素濃度は１３．７ｐｐｍａ−ＪＥＩＴＡと求まった。そこで、電子線を照射しなかった残りのサンプルをＦＴ−ＩＲ測定のリファレンスとした。
(Example 4)
Unlike Example 3, the reference was a CZ silicon crystal, and the oxygen concentration of this reference was first determined by the same method as in Example 3. That is, a double-sided polishing sample having a thickness of 2 mm was prepared from a CZ crystal having a diameter of 300 mm. First, the carbon concentration was measured by the SIMS method, and it was determined to be 4.3 × 10 14 atoms / cm 3 . Next, this was divided into two, one of which was irradiated with an electron beam, and the oxygen concentration was determined by the method described above. That is, when an electron beam was irradiated at an acceleration voltage of 2 MV and an irradiation amount of 1.0 × 10 15 ejectrons / cm 2 and PL measurement was performed at a liquid helium temperature, G-ray intensity = 2284 (au), C-ray intensity =. It was obtained as 32342 (a.u.). These By substituting the above equation (2) (proportional constant is 2.25 × 10 -15), the oxygen concentration of the sample was Motoma' the 13.7ppma-JEITA. Therefore, the remaining sample not irradiated with the electron beam was used as a reference for FT-IR measurement.
測定サンプルとしては、実施例３と同じものを用いた。このサンプルの酸素濃度も実施例３と同様のＦＴ−ＩＲ法で求めたところ、Ｏｉピークは凹形状（すなわち、負の差濃度）で、差濃度は、−１．１７ｐｐｍａと求まった。従って、絶対濃度は、リファレンスの濃度と上記で求めた差濃度の和として、１２．５３ｐｐｍａと求められ、実施例３の結果と同等であった。 As the measurement sample, the same one as in Example 3 was used. When the oxygen concentration of this sample was also determined by the same FT-IR method as in Example 3, the Oi peak was determined to have a concave shape (that is, a negative difference concentration), and the difference concentration was determined to be -1.17 ppma. Therefore, the absolute concentration was determined to be 12.53 ppma as the sum of the reference concentration and the difference concentration obtained above, which was equivalent to the result of Example 3.
（比較例１）
実施例１と同じリファレンス、測定サンプルを用いて、従来のＦＴ−ＩＲ法（すなわち、差濃度のみで不純物濃度を特定）で炭素濃度を求めたところ、実施例１に記したように５．２×１０１４ａｔｏｍｓ／ｃｍ３であり、絶対濃度との乖離が見られた。
(Comparative Example 1)
When the carbon concentration was determined by the conventional FT-IR method (that is, the impurity concentration was specified only by the difference concentration) using the same reference and measurement sample as in Example 1, 5.2 as described in Example 1. It was × 10 14 atoms / cm 3 , and a deviation from the absolute concentration was observed.
（比較例２）
実施例２と同じリファレンス、測定サンプルを用いて、炭素濃度についてＦＴ−ＩＲ測定したところ、実施例２に記したようにＣｓピークが凹形状（すなわち、負の差濃度）になってしまい、炭素濃度を定量できなかった。
(Comparative Example 2)
When FT-IR measurement was performed on the carbon concentration using the same reference and measurement sample as in Example 2, the Cs peak became concave (that is, negative difference concentration) as described in Example 2, and carbon. The concentration could not be quantified.
（比較例３）
実施例３と同じリファレンス、測定サンプルを用いて、従来のＦＴ−ＩＲ法（すなわち、差濃度のみで不純物濃度を特定）で酸素濃度を求めたところ、実施例３に記したように１２．３０ｐｐｍａであり、絶対濃度との乖離が見られた。
(Comparative Example 3)
When the oxygen concentration was determined by the conventional FT-IR method (that is, the impurity concentration was specified only by the difference concentration) using the same reference and measurement sample as in Example 3, 12.30 ppma as described in Example 3. Therefore, a deviation from the absolute concentration was observed.
（比較例４）
実施例４と同じリファレンス、測定サンプルを用いて、酸素濃度についてＦＴ−ＩＲ測定したところ、実施例４に記したようにＯｉピークが凹形状（すなわち、負の差濃度）になってしまい、酸素濃度を定量できなかった。
(Comparative Example 4)
When FT-IR measurement was performed on the oxygen concentration using the same reference and measurement sample as in Example 4, the Oi peak became concave (that is, negative difference concentration) as described in Example 4, and oxygen. The concentration could not be quantified.
なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は、例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。 The present invention is not limited to the above embodiment. The above embodiment is an example, and any one having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. It is included in the technical scope of the invention.
Claims (1)
ＦＴ−ＩＲ法により不純物濃度を求めるに際し、あらかじめＰＬ法により不純物濃度が求められている試料をリファレンスとし、測定サンプルと前記リファレンスとの差スペクトルから前記測定サンプルと前記リファレンスの不純物の差濃度を求め、これに前記リファレンスの不純物濃度を足すことで、前記測定サンプルに含まれる不純物である炭素または酸素の絶対濃度を求めるとき、
前記不純物が炭素の場合、粒子線を照射した検量線用サンプルをＰＬ測定して得られるＧ線強度、Ｃ線強度、および別に求めた炭素濃度、酸素濃度を用いて、関係式（１）である炭素濃度＝比例定数×酸素濃度×（Ｇ線強度／Ｃ線強度）を満たすような比例定数をあらかじめ求めておき、前記リファレンスに前記ＰＬ測定と同条件で粒子線を照射し、前記ＰＬ測定と同条件でＰＬ測定して得られるＧ線強度、Ｃ線強度、および別に求めた酸素濃度を前記関係式（１）に代入することで前記リファレンスの炭素濃度を求め、
前記不純物が酸素の場合、粒子線を照射した検量線用サンプルをＰＬ測定して得られるＧ線強度、Ｃ線強度、および別に求めた炭素濃度、酸素濃度を用いて、関係式（２）である酸素濃度＝比例定数×炭素濃度×（Ｃ線強度／Ｇ線強度）を満たすような比例定数をあらかじめ求めておき、前記リファレンスに前記ＰＬ測定と同条件で粒子線を照射し、前記ＰＬ測定と同条件でＰＬ測定して得られるＧ線強度、Ｃ線強度、および別に求めた炭素濃度を前記関係式（２）に代入することで前記リファレンスの酸素濃度を求めることを特徴とする不純物濃度の測定方法。 It is a method for measuring the impurity concentration in which the impurity concentration in a silicon single crystal is obtained by the FT-IR method.
When determining the impurity concentration by the FT-IR method, the sample for which the impurity concentration has been determined in advance by the PL method is used as a reference, and the difference concentration of impurities between the measurement sample and the reference is obtained from the difference spectrum between the measurement sample and the reference. , When the absolute concentration of impurities carbon or oxygen contained in the measurement sample is obtained by adding the impurity concentration of the reference to this,
When the impurity is carbon, the G-ray intensity and C-ray intensity obtained by PL measurement of a calibration curve sample irradiated with particle beams, and the separately obtained carbon concentration and oxygen concentration are used in the relational expression (1). A proportionality constant satisfying a certain carbon concentration = proportionality constant × oxygen concentration × (G-ray intensity / C-ray intensity) is obtained in advance, and the reference is irradiated with a particle beam under the same conditions as the PL measurement, and the PL measurement is performed. By substituting the G-ray intensity and C-line intensity obtained by PL measurement under the same conditions as above, and the oxygen concentration obtained separately into the relational expression (1), the carbon concentration of the reference was obtained.
When the impurity is oxygen, the G-ray intensity and C-ray intensity obtained by PL measurement of a calibration curve sample irradiated with particle beams, and the separately obtained carbon concentration and oxygen concentration are used in the relational expression (2). A proportionality constant satisfying a certain oxygen concentration = proportionality constant × carbon concentration × (C-ray intensity / G-ray intensity) is obtained in advance, and the reference is irradiated with a particle beam under the same conditions as the PL measurement, and the PL measurement is performed. The oxygen concentration of the reference is obtained by substituting the G-ray intensity and C-line intensity obtained by PL measurement under the same conditions as above, and the separately obtained carbon concentration into the relational expression (2). Measurement method.
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