Abatement of CF/sub 4/, C/sub 2/F/sub 6/, and CHF/sub 3/ in microwave generated surface wave plasmas

Summary form only given, as follows. Fluorocompounds (FCs) such as CF/sub 4/, C/sub 2/F/sub 6/, and CHF/sub 3/ are extensively used in semiconductor industry for plasma etching and CVD chamber cleaning. Due to their strong infrared absorption and long atmospheric lifetimes, these fluorocompounds have great global warming potential, and therefore, significant efforts have been made to reduce their release to the environment. In this study, CF/sub 4/, C/sub 2/F/sub 6/, and CHF/sub 3/ were destructed individually in a microwave-generated surface wave plasma reactor using oxygen as the main additive gas. The composition of the effluent stream was analyzed using FTIR. The effects of oxygen percentage in feed, input power, and operating pressure on the destruction efficiency and product distribution of the plasma abatement process were investigated. The effects of argon or hydrogen as a second additive gas were also examined. It was found that higher destruction efficiency occurs at high microwave powers, medium oxygen percentage, and low operating pressures. Over 99% destruction efficiency can be achieved for all three fluorocompounds under optimized conditions. The destruction of CHF/sub 3/ was much easier than that of CF/sub 4/ and C/sub 2/F/sub 6/. However, the plasma abatement of CHF/sub 3/ and C/sub 2/F/sub 6/ showed significant amounts of CF/sub 4/ produced in the effluent. Thus, rather than the destruction efficiency, the reduction of MMTCE (Million Metric Tons Carbon Equivalents) was evaluated as the index of reduction of greenhouse effect in each abatement experiment. The addition of argon was found to enhance the C/sub 2/F/sub 6/ destruction while reducing the CF/sub 4/ generation. As a result, the reduction of MMTCE increased with the argon addition in C/sub 2/F/sub 6/ abatement. Regarding the CHF/sub 3/ abatement, it was found that the hydrogen addition could effectively reduce the CF/sub 4/ formation and hence the MMTCE was greatly reduced. But the amount o- hydrogen should not exceeds the amount of oxygen otherwise a fluorocarbon film would deposit on the sidewall of the plasma tube and the destruction efficiency of CHF/sub 3/ would drop drastically. Detailed reaction mechanisms of the plasma abatement of CF/sub 4/, C/sub 2/F/sub 6/, and CHF/sub 3/ are currently under investigation.