[labnetwork] PECVD dilute gas question(s)

[Iulian Codreanu]

Hi Nathan,

Please see below for some thoughts.

A diluted SiH4 cylinder is considered by some folks safer but other 
folks disagree. Some things to consider are the number of cylinder 
changes and that SiH4 mixtures can explode if allowed to accumulate 
inside various enclosures.

A diluted SiH4 will require higher gas flows, which are easier to 
control via the MFC because you can operate closer to its mid range.

An additional line for pure He can be used to control film stress.

Cheers!

iulian Codreanu, Ph.D.
Director, Nanofabrication Facility
University of Delaware
Harker ISE Lab, Room 163
221 Academy Street
Newark, DE 19716
302-831-2784
https://udnf.udel.edu

On 4/7/2025 9:49 AM, Nathan Aultman wrote:
>
> 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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