POST-PUMP PFC ABATEMENT BY ATMOSPHERIC MICROWAVE PLASMAS: COMPLETION OF METAL ETCH BETA TEST

摘要

A post-pump PFC abatement technology by surface-wave microwave plasma was evaluated at the exhaust of an SF_6 tungsten etch tool on a production line. The CLEANSENS~(~R) portable gas analyzer was qualified as a convenient alternative to QMS and FTIR to allow for routine acquisition of large series of residual PFC concentration measurements. As evidenced by previous laboratory studies, the total flow rate imposed by N_2 ballasting of primary pumps is the dominant factor influencing the abatement efficiency. After optimization, abatement rates in excess of 99% can be obtained for up to 3 chambers plugged with, possibly, a short-term technical evolution for substantially more demanding applications. After some initial problems due to vacuum and exhaust management at the fab scale, an endurance test was conducted on a 24 hr basis for more than 1000 hrs. Condensates generation due to complex chemistry intrinsic to the SF_6/W etch process was not found to be a serious downtime factor. The discharge tube and its dielectric cooling fluid did not undergo any sign of modification or degradation and the abatement efficiency remained stable over time.