以高溫微波電漿火炬轉化四氟甲烷與六氟化硫之研究

Reforming of Perfluoromethane and Sulfur- hexafluoride Using Microwave Plasma Torch

鄭為允(Wei-Yun Cheng)

指導教授 ： 魏大欽

中原大學/工學院/化學工程學系/碩士(2007年)

https://doi.org/10.6840/cycu200700505

摘要

本研究利用高溫電漿火炬進行對CF4與SF6兩種全氟溫室氣體轉化，並利用傅立葉轉換紅外線光譜儀進行產物分析，探討O2進料流量、載氣流量、微波功率與全氟化物進料濃度對轉化效果與產物生成之影響，研究中並針對全氟化物建立一反應熱力學模型，將其計算結果與實驗值相比較，藉由轉化率與產物組成來預估反應器之反應溫度並驗證模型準確性，最後利用PECVD系統模擬半導體實廠測試，評估高溫火炬電漿應用於半導體廠全氟廢氣削減之可行性。
研究發現，添加與全氟化物等比例的O2可以有效抑制CFx及SFy自由基與F原子的再結合反應，維持電漿實際之解離效果；提高全氟化物進料濃度(流量)會使轉化效果降低，但能量使用效率則較高；另外載氣流量與微波功率決定電漿火炬反應器之溫度，提高微波功率或降低載氣流量皆可提高反應器溫度，使轉化效果提升。
將熱力學模型計算値與實驗結果進行比較，可預估本研究削減CF4的溫度介於1400~1800 K間，而SF6則介於1200~1500 K間；CO、NO、SOF2及SO2F2之模型計算值與實驗值有所差異，主要由於上列物種可能於冷卻腔體或管線中持續與O2反應，使產物趨勢發生變化；其餘產物趨勢皆與實驗值相近，證明本研究之熱力學模型具相當之準確性。
利用PECVD系統模擬蝕刻/腔體清潔之製程尾氣，發現PECVD系統對SF6的解離效果不佳，因此將製程尾氣導入電漿火炬進行削減，藉由調整微波功率可使轉化效果達90%以上，證明高溫電漿火炬應用於半導體全氟廢氣削減具有極佳之效果。

關鍵字

電漿火炬 ； 全氟化物削減

並列摘要

Abatement of CF4 and SF6 using microwave plasma torch was investigated. A series of experiments were conducted to determine the destruction efficiency and product distributions over different operation parameters. In the meanwhile, an equilibrium model was developed using Chemkin IV to simulate plasma processes. The model results were compared with experimental measurements.
Experimental result showed that CF4 and SF6 could be effectively removed in N2 plasma torch. A decrease in N2 sheath gas flow rate and an increase of microwave power increase the gas temperature, resulting in the increase of reactant conversion. The abatement of SF6 is more effective than that of CF4. In this research, the amount of O2 inlet also determine the destruction efficiency, sufficient O2 can generate lots of O radical to react with CFx and SFx radical and then inhibit the recombination reaction and obtain high destruction efficiency.
A thermodynamic model was developed to calculate the equilibrium composition in plasma torch system. By comparing experimental data with model predictions, it was found that the thermodynamic model is able to capture most of the experimentally observed trends. Over 99.9% destruction efficiency can be achieved for CF4 and SF6 abated at 1800 K and 1600 K, respectively, with equimolar O2 addition.
Finally, a PECVD chamber is connected in series with the plasma torch to simulate the effluent abatement of plasma etching/chamber cleaning process in real fabs.

並列關鍵字

Perfluorocompounds

參考文獻

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