脈衝雙頻率電容耦合式電漿流體模型之數值研究

Abstract

雙頻率電容耦合式電漿源在半導體蝕刻製程是不可或缺的工具，比起傳統的單頻率電容耦合式電漿源，雙頻率電容耦合式電漿源能夠分別地控制離子能量分佈以及轟擊基板的離子通量。然而，隨著電子線路尺寸的微小化，單單使用雙頻率電容耦合式電漿源已無法蝕刻高深寬比的洞、溝槽。於是能有效改善蝕刻輪廓的脈衝雙頻率電容耦合式電漿源逐漸被發展出來。 本論文運用本實驗室發展的平行化二維軸對稱電漿流體模型對脈衝雙頻率電容耦合式氬氣放電電漿作數值研究。統御方程式包括連續方程式、基於漂移擴散近似的動量方程式、泊松方程式以及電子能量方程式，使用半隱式有限體積法離散以及利用區域切割作平行計算，在計算期間透過MPI函式庫作資料交換。模擬目的為探討多頻率電容耦合式電漿源電漿物理現象以及改善電漿均勻度，結果顯示利用兩電源間相位差和增加極板間距離能明顯地影響電漿分佈， 然而調整上極板的半徑大小無助於電漿均勻性。

The dual-frequency capacitively coupled plasma (DF-CCP) is a powerful tool for semiconductor processing etching. As compared to conventional single-frequency CCP, DF-CCP have an advantage of separately controlling the ion energy distributions (IEDs) and the ion flux to the substrate electrode. However, with the miniaturization of the microelectronic fabrication, DF-CCP cannot meet the strict requirements of high-aspect-ratio hole or trench etching anymore. Thus, DF-CCP with pulsed operation has been developed and was found to improve etched profile significantly. This thesis numerically investigates pulsed dual-frequency capacitively coupled argon discharge using a parallel 2-D axisymmetric plasma fluid model which has been developed by our group. The governing equations, including continuity equations, momentum equations based on drift-diffusion approximation for all charged species, Poisson equation and electron energy equation, are discretized through semi-implicit cell-centered finite-volume method and are parallelized with domain decomposition using message passing interface (MPI). The objective of the thesis is to study the physical phenomena of plasma in pulsed dual-frequency CCP and to improve the plasma uniformity. The results show that modulating the phase shift between dual-frequency powers and increasing the space of gap can affect plasma uniformity. However, adjusting the radius of grounded electrode is not useful in improving plasma uniformity.