AVS 45th International Symposium
    Plasma Science and Technology Division Monday Sessions
       Session PS1-MoA

Invited Paper PS1-MoA3
Plasma Etching Using PFC Replacement Chemicals

Monday, November 2, 1998, 2:40 pm, Room 314/315

Session: Environmental Issues and Emerging Technologies
Presenter: Y. Goto, Hitachi Ltd., Japan
Authors: T. Kure, Hitachi Ltd., Japan
T. Takaichi, Showa Denko K.k., Japan
Y. Goto, Hitachi Ltd., Japan
Correspondent: Click to Email
PFC (Perfluorocompound) gases are widely used for plasma etching of thin film and for plasma cleaning of process chamber. However, unfortunately, PFCs have extremely long atmospheric lifetimes and absorb infrared radiation emitted by the earth that would otherwise be radiated into space. As a result, PFCs contribute to the greenhouse effect in the earth's atmosphere, thus helping to cause the phenomenon known as a global warming. To reduce the release of PFCs into the air, replacement chemicals and abatement devices for exhaust gases need to be developed. Recently, several kind s of abatement devices (combustion, plasma, thermal, and catalyst reaction) are being examined. In our research, we have focused on using iodofluorocarbons (IFCs) and unsaturated fluorocarbons (u-FCs) as replacement chemicals for PFCs. Since the binding energy of C-I bond and C=C bond are very weak compared with the C-F bond, the atmospheric lifetimes of IFCs and u-FCs are extremely short. Therefore, their impact on global warming should be small. For use in SiO@sub 2@ etching, we selected C@sub 2@F@sub 5@I and C@sub 3@F@sub 6@ because of its C/F ratio about 0.5, its boiling point less than room temperature, and nonflammability. We evaluated the SiO@sub 2@ and poly-Si etching rate in a microwave plasma with these gases comparing it with C@sub 4@ F@sub 8@ gas. We also evaluated XPS spectrum of deposited polymer on etched wafers. We found that both the etching performance and deposited material were similar among these gases. Therefore, we believe C@sub 2@F@sub 5@I and C@sub 3@F@sub 6@ can be used as replacement chemicals for PFCs in SiO@sub 2@ etching.