- 學位論文
八氟環丁烷電漿應用於二氧化矽蝕刻製程之模型研究
Modeling Study on SiO2 Etch Process Using c-C4F8 Plasma
摘要
氟碳電漿廣泛運用於各類半導體或光電產業之電漿蝕刻製程，其中又以蝕刻二氧化矽最為普遍，本研究針對目前最廣為使用的八氟環丁烷氟碳電漿，建立出具有氣相與表面相的反應機構，並提出一個有別於傳統的表面相反應機制，其包含氟碳膜的沉積、氟碳膜的濺擊與二氧化矽的蝕刻，以預測沉積在晶圓表面的氟碳層厚度及其與二氧化矽蝕刻速率的相關性，並與文獻實驗值做對照。探討操作參數（電漿源功率、操作壓力、進料流率以及偏壓）對於電漿性質（電子密度、電子溫度、物種濃度、蝕刻速率與氟碳膜厚度）的變化。 在文獻比較方面，模型預測之蝕刻速率與實驗值趨勢一致且相當接近，也成功預測氟碳膜厚度變化，離子電流密度也與文獻值相當貼近。在電漿參數的探討方面，電漿性質在不同的功率下有較大的影響，氟碳膜厚度隨著功率改變具有先升後降的情形、電子溫度幾乎不隨功率改變、C4F8之解離率隨著功率的增加而增大；而壓力的增加，有利於氟碳膜的沉積，卻不利於蝕刻速率的提升，在低壓時有較大的蝕刻速率、解離率與電子溫度；進料流率對於氟碳膜厚度、電子溫度與C2F4濃度的影響並不顯著，隨著流率的增加，解離率與CF2+離子濃度會下降，而C2F4+離子濃度則會上升；隨著偏壓的增強，蝕刻速率增加而氟碳膜厚度則變薄，因蝕刻速率變快，大量消耗離子，而使CF2+離子濃度些微下降。
並列摘要
Fluorocarbon plasma etching of silicon dioxide has been widely used in semiconductors and optoelectronics industries. A novel reaction mechanism on c-C4F8 plasma consisting of gas phase and surface phase reaction is developed in this study. The surface reaction mechanism includes deposition of fluorocarbon film, sputtering of fluorocarbon film and etching of silicon dioxide to predict the relationship between deposition of fluorocarbon and silicon dioxide etching induced by ion bombardment. The modeling results are compared with existing experimental data to verify the consistency. Furthermore, the influence of parameter variations such as power, operating pressures, inlet flow rate and bias voltage on plasma characteristics e.g. electron density, electron temperature, species concentration, etching rate and thickness of fluorocarbon film are investigated using the model. The results indicate that the model can successfully predict the thickness of fluorocarbon film and ion current density. Based on the results, the thickness of the fluorocarbon increases as the wattage of the plasma source is increased, thus the thickness is directly proportional to the plasma power source. Moreover, the degree of the dissociation of C4F8 is also directly proportional to the plasma power source however, there is no significant change in the electron temperature as the plasma power source is varied. On the other hand, when the pressure is increased, it facilitates the deposition of fluorocarbon film. The etching rate, degree of dissociation, and electron temperature at lower pressure are better than at high pressure. Also, when the inlet flow rate is increased, the concentration of the CF2+ is decreased but the concentration of C2F4 is increased. Finally, it is observed that an increase in the bias voltage would result in an increase in the etching rate, as a result, the fluorocarbon film becomes thinner and the concentration of CF2+ is reduced.