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衝突輻射モデル（以下，CRモデル）に基づき，プラズマの電子温度・密度を非侵襲的に診断する方法は，原則として可能である．しかし，実際のプロセスプラズマにおいては，プロセスガス混入による励起状態への影響が懸念される．そこで本研究では，プロセスプラズマにしばしば用いられる低気圧Arプラズマについて，酸素分子混入を想定した損失項をArCRモデルに組み込むことで，励起状態数密度に生じる影響を理論計算により考察した．, Diagnostic techniques for measuring the state of the plasma are important for accurate control of the process plasma.According to previous studies, "a method of non-invasively diagnosing the temperature and density of electrons from the number density of excited states obtained by emission spectroscopy based on the collision emission (CR) model" is possible in principle.However, in actual process plasma, there is a concern that the mixing of process gas will affect the excited state. Therefore, in this study, we investigated the effect on the number density of excited states by incorporating a loss term assuming oxygen molecule contamination into the ArCR model of low-pressure Ar plasma, which is often used for process plasma.

非平衡プラズマ診断において，発光分光計測のため診断モデルは個別論的にならざるを得ない．計測対象とするパラメータ範囲を初期条件として与えれば，同範囲に対する最適な診断モデルを提示するアルゴリズムを考案した．診断モデルに内在する理論上の診断誤差を求めた．換算占有密度の未知パラメータ依存性に顕著な不単調性を呈した生成条件下において，診断誤差が大きくなった．, In non-equilibrium plasma diagnostics, it is difficult to obtain the general diagnostic model for optical emission spectroscopic measurement. In this work, an optimization algorithm was proposed for plasma diagnostic modeling under plasma conditions set according to the target of measurement. The theoretical diagnostic error was analyzed. It was found that the diagnostic error was increased under the condition where the reduced population density dependence of unknown parameters was shown to be non-monotonic.

衝突輻射モデルに基づき、電子温度・密度診断モデルを作成し、発光分光計測によりその診断モデルの有用性を検証した。対象としたのは低気圧マイクロ波放電Arプラズマである。電子温度は5p及び6p準位、電子密度は4s、4p及び5s準位を用いて診断モデルを作成した。また、モデル作成に際し、電子のエネルギー分布はMaxwell分布もしくはDruyvesteyn分布を仮定した。プローブ計測と診断結果を比較したところ、大略が一致する計測を行うことが出来た。, Diagnostic models of the electron temperature and density are developed for low-pressure microwave discharge Ar plasma based on the collisional radiative model, and the applicability of the diagnostic models is verified by optical emission spectroscopy. The diagnostic models of the electron temperature and density are described by Ar excited levels 5p, 6p and 4s, 4p, 5s, respectively. When developing the diagnostic models, the electron energy distribution function is assumed to be a Maxwell or a Druyvesteyn one. Comparison with the probe measurement reveals that the diagnostic results of the proposed method roughly agree with those of the probe measurement.

近年、トモグラフィを用いた診断が報告されつつある。しかし、原子分子過程を詳細に考慮した報告がなく、解析に起因する不確かさが著しいことが課題であった。本研究では、アルゴン誘導結合プラズマを対象にトモグラフィック発光分光計測を実施した。原子分子過程を詳細に記述できる原子分子過程モデルである、衝突輻射モデルに基づいて解析した。これにより、電子温度・電子密度の空間分布診断を定量的に実現した。, In recent years, tomography-based diagnostics have been reported. However, no reports have considered atomic-molecular processes in detail, and the significant uncertainty was caused by excitation-kinetic analysis. In this study, argon inductively coupled plasma by tomographic optical emission spectroscopic measurement. The excitation-kinetics analysis was based on the collisional radiation model, one of the atomic-molecular process models which can describe atomic-molecular processes in detail. A quantitative diagnosis of the spatial distribution of electron temperature and electron density has been produced.

エッチング装置で生成したアルゴン低気圧誘導結合プラズマの電子温度Te，電子密度Neおよび電子エネルギー分布関数(EEDF)を，発光分光計測により診断した．診断誤差を低減するため，励起準位数密度分布に対するTe，Ne, EEDFの依存性を分析し，この結果に基づいて診断に用いる励起準位を選定した．上準位4p[1/2]1，4p’[3/2]1，4p[1/2]0，4p’[1/2]0の発光線に基づいて算出した励起準位数密度分布を，衝突輻射モデルから求めた理論値とフィッテングして診断を行った．, Electron temperature Te, density Ne, and energy distribution function (EEDF) of the argon low pressure inductively coupled plasma generated by an etching unit were diagnosed by optical emission spectroscopic measurement. In order to reduce diagnostic errors, the dependence of reduced population density distribution on Te, Ne, and EEDF was surveyed. The excitation levels which used for diagnosis were selected based on the survey result. The diagnosis was based on fitting reduced population densities with calculated value by collisional-radiative model and experimental value by OES measurement of emission lines which upper levels were 4p[1/2]1, 4p’[3/2]1, 4p[1/2]0, and 4p’[1/2]0.

連続スペクトルにより、大気圧非平衡アルゴンプラズマの電子温度・密度の計測可能性を研究した。放電空間を限定できる放電装置を用い、絶対校正済の測定系で発光分光計測を実施した. このスペクトルを理論曲線でフィッティングする。Druyvesteyn 電子エネルギー分布関数を仮定すると適切な値が導出された。衝突輻射モデルによる励起状態密度と線スペクトル強度とのクロスチェックにより、妥当性を確認した。, The feasibility of spectroscopic measurement of electron temperature and density of atmospheric-pressure non-equilibrium argon plasma was investigated, applying optical emission spectroscopic measurement of a continuum spectrum due to electron-atom bremsstrahlung. Emission spectroscopy was performed with an absolutely calibrated measurement system using a discharge device that can limit the discharge space to one point. The obtained spectrum is fitted with a theoretical curve. Assuming the Druyvesteyn electron energy distribution function, appropriate electron temperature and density were derived. The validity was confirmed by the cross-check between the line spectral intensity and the excited state density calculated with the Ar collisional radiative model with atomic collisional processes.

ウエハ表面クリーニング用途に使用される大気圧アルゴンプラズマジェットの電子温度及び電子密度を診断した．上準位4p’[3/2]1，4p’[1/2]1，4p[1/2]0，4p’[1/2]0の発光線に基づいて算出した励起準位数密度分布を，衝突輻射モデルから求めた理論値とフィッテングして診断を行った．放電管の下流になるにつれて，電子温度，電子密度ともに低下した．, Electron temperature and density of the atmospheric pressure argon plasma jet for surface cleaning of wafers were diagnosed based on optical emission spectroscopic measurement. The diagnose was based on fitting with the excitation-level number density distribution of the theoretical value based on the collisional-radiative model and the experimental value based on the optical emission lines which upper levels are 4p’[3/2]1, 4p’[1/2]1, 4p[1/2]0, and 4p’[1/2]0 . The electron temperature and density were decreased in the downstream of discharge tube.

大気圧下でも適用可能な非平衡プラズマの電子温度・密度計測法には，簡便・安価な実用法として期待される発光分光計測法がある．本稿では，その中でも重要と考えられる2 つの方法，衝突輻射（CR）モデルに基づいた線スペクトル強度測定法，および電子-中性粒子制動放射による連続スペクトル測定法につい て，その原理と実測例を紹介する．特に前者については，モデル計算の結果を実際の分光測定結果に実用レベルで適用するための手法として，「主要素過程抽出法」，「2 線対法」，そして「励起温度換算法」の3 手法を紹介する．最後に，連続スペクトル計測による実測例を紹介し，この方法ならば原理的には電子エネルギー分布関数（EEDF）をも求められることに触れ，今後の研究展望を述べる．, We describe the principles and applications of two essential methods for measurement of electron temperature and the density of non-equilibrium plasmas including atmospheric-pressure discharge, based on optical emission spectroscopic (OES) measurement, i.e., line intensity measurement assisted with a collisional radiative model, and continuum spectrum measurement as electron-neutral bremsstrahlung. For the former scheme, we introduce three practical procedures to interpret the OES results based on the excitation kinetic model, which are the “selection of the dominant elementary processes”, the “measurement of two pairs of line intensities”, and the “conversion of the excitation temperature to the electron temperature”. In the last part, examples are shown for the demonstration of the continuum measurement, which has the potential to deduce the electron energy distribution function, followed by its future prospects.