[labnetwork] N2 pump purge source of chamber contamination?

[Vito Logiudice]

Dear Colleagues,

We are depositing single crystal diamond via PECVD in a newly purchased tool dedicated to this process. Initial deposition runs have revealed the presence of film defects caused by stray nitrogen. The system and process gas lines have been helium leak-tested. The load-locked process chamber is pumped down by a turbo pump backed by a nitrogen-purged dry pump (the process makes use of methane and hydrogen). We're wondering if the N2 purge on the roughing pump might somehow be contributing to the problem.

I'd appreciate hearing the community's thoughts on the possibility of nitrogen back flow from an N2-purged roughing pump back to the process chamber.

Many thanks,
Vito
--
Vito Logiudice  M.A.Sc., P.Eng.
Director of Operations, Quantum NanoFab
University of Waterloo
200 University Avenue West
Waterloo, ON      Canada   N2L 3G1
Tel:  1-519-888-4567  ext. 38703
Email: vlogiudi at uwaterloo.ca<mailto:vlogiudi at uwaterloo.ca>
Website: https://qncfab.uwaterloo.ca/

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