John,

     SF6 as a plasma breaks down to S and 6 F's.  If the S sees O2
common in atmosphere you get SO2.  If this sees H2O common in atmosphere
you get H2SO3, Sulphurous acid.  We had a vacuum pump that almost
dissolved in 13 months caused by H2SO3.  If you use oil pumps, filters
for the oil, stop this problem.  The customer who experienced this
problem first on his plasma systems has been running for 15 years with
multiple systems with filters with no problems.  The same plasma systems
have cosmetic problems with acid eroded pits in the vacuum chambers but
it is only a cosmetic problem.

Bill Moffat

-----Original Message-----
From:  Brent Garber
Sent: Wednesday, July 07, 2010 7:17 AM
To: General MEMS discussion
Subject: Re: [mems-talk] SF6 / BCl3 issue

John,

I use both BCl3 and SF6 everyday in my RIE.  You didn't state whether
you are etching GaAs and want to stop on AlGaAs or the other way around.
I also need to know you Al%

Brent


John Montoya wrote:
> Hello everyone.
>
> I am trying to perform a selective GaAs / AlGaAs etch.  I recently put
> in a request to my cleanroom manager to incorporate SF6 and BCl3 onto
> our PlasmaTherm SLR750 series ICP/RIE machine.  For some unexplained
> reason, I was denied from putting SF6 and BCl3 onto our machine.
>  Does anyone know of any safety or contamination issues associated
> with these two gases?  Please help.
>
> Sincerely,
> John