[labnetwork] PECVD dilute gas question(s)

[Paolini, Steven]

SiH4 diluted in Helium poses pumping challenges. Helium is notoriously hard to pump with a turbo and the large amount of mixture needed to grow Si films leads to problems with pressure control and deposition rates. I know I will attract some arguments against using 100% SiH4 but the main reason to use a pure mixture is to reduce the amount of cylinder changes that are well documented as being the main source of accidents.
Equipment Dood.
Steve Paolini
________________________________
From: labnetwork <labnetwork-bounces at mtl.mit.edu> on behalf of Nathan Aultman <naultman at creol.ucf.edu>
Sent: Monday, April 7, 2025 10:49 AM
To: labnetwork at mtl.mit.edu <labnetwork at mtl.mit.edu>
Subject: [labnetwork] PECVD dilute gas question(s)


Hello Labnetwork,



We have a PECVD system using dilute silane (2%)/N2.  Some labs with similar systems use dilute silane (5%)/helium.  We are nearing the end of our current cylinder and will need a replacement soon.  What are the advantages and disadvantages when choosing the dilute gas?  Does choosing a helium mixture produce more desirable films and/or quality?  In other words, is it worth it to purchase a cylinder with helium?  Also, what would be the reason(s) for using helium as an additional process gas?  E.g., a separate MFC and gas line.



Thank you all in advance.



Nathan C. Aultman

University of Central Florida

407-823-6852

naultman at creol.ucf.edu<mailto:naultman at creol.ucf.edu>


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