[labnetwork] Johnson Matthey H2 Purifier

[Rachel Schoeppner]

Good Morning, 


We have a Johnson Matthey HP-25 hydrogen purifier that we suspect is not functioning properly. In its idle state it is kept under low UHP N2 flow, and we think that some of this is getting through the purifier into the lines of our CVD. At the start of deposition when we start H2 flow and ignite the initial plasma we see an unexpected peak in nitrogen (verified both in the emission spectrum of the plasma as well as nitrogen that is incorporated in the epitaxial film as measured with SIMS). When we flow the hydrogen gas through the growth chamber for ~20 min before deposition, no nitrogen peak is observed, suggesting that it is coming in as an initial “plug” through the purifier at the very beginning that can be flushed through. There is also a low amount of background nitrogen throughout the deposition (this could be an impurity in the methane, but I am not sure how likely that is). 

We have leak checked the line running from the purifier to the CVD chamber and cannot detect any leaks that might be causing the initial nitrogen spike.

We are wondering if anyone has experience with these purifiers or ideas on how to diagnose their proper functionality. If it is letting unwanted species through, then what would be our options for fixing or replacing it?


Thank you!


Rachel

—                                                    

Rachel Schoeppner, Ph.D

Nanostructure Cleanroom Facility Manager
California NanoSystems Institute (CNSI)
University of California, Santa Barbara
rlschoeppner at ucsb.edu
rachel at cnsi.ucsb.edu
(805)893-2296











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