Effect of O-2(CO2)/C4F8O gas combinations on global warming gas emission in silicon nitride PECVD plasma cleaning

In this study, O-2/C4F8O and CO2/C4F8O have been used as the chemicals for plasma-enhanced chemical vapor deposition (PECVD) chamber-cleaning of silic on nitride, and the effects of gas mixture and operational pressure on the silicon-nitride cleaning rate and emission properties, such as emission spe cies, destruction and removal efficiencies (DREs), and million metric tons of carbon equivalent (MMTCE), have been investigated. O-2/C4F8O generally s howed a higher silicon-nitride cleaning rate compared to CO2/C4F8O, possibl y due to the removal of fluorine by carbon in CO2. The highest silicon-nitr ide cleaning rate obtained with O-2/C4F8O was approximately 600 nm/min for 80% O-2/20% C4F8O at 66.7 Pa (500 mtorr), 40 sccm, 150 W of 13.56-MHz RF po wer, and without substrate heating. Emission species, such as CF4, COF2 and CO2, were observed through the exhaust line during silicon nitride cleanin g, in addition to the undestructed remaining feed gases. The quantities of these emission species were higher than that of C4F8O fed through the clean ing chamber. With 80% O-2/20% C4F8O, the highest DREs and the lowest MMTCE obtained were 92% and 3 X 10(-10) respectively. In the case of CO2/C4F8O, s ilicon nitride cleaning rates were lower, the DRE was lower and MMTCEs were higher than those of O-2/C4F8O. (C) 2001 Elsevier Science B.V. All rights reserved.