[labnetwork] STS DRIE Multiplex Lip Seal failures

[Noah Clay]

Mark,

I have seen blackening on the back of the wafer when clamping is poor.  Most recently, this was due the e-chuck having been etched excessively and/or polymer redep on the chuck from the endpoint clean step (cleans used to be run without a wafer; we now use SiC).  

What are your backside He leak rate set points and actual values?  We run our etch process at -5C...(SPTS Rapier platform).

Thanks,
Noah

Sent from my iPhone

> On Mar 5, 2019, at 15:44, Mark Weiler <mweiler at andrew.cmu.edu> wrote:
> 
> Hello Everyone,
> 
> We have gone through seven new lip seals purchased form Orbotech/SPTS.  They are often failing before we even finish qualifying the system, or within a month thereafter.
> 
> Our our process is stable with power and parameters not deviating over the past decade.  However, I ordered the most recent batch of lip seals because the wafer seals we had been using were coming out with black residue after only a few runs… however, the current ones do the same.  Not only have the lips seals disintegrated, but the chamber lid o-ring and bottom ceramic spool o-ring have also failed with black rubber material shedding off.  It’s as if they are made of Buna and not meant for this application.
> 
> Our process is typical Bosch with 100 sccm C4F8 and 20 sccm O2 for etching switching off with ~50 Sccm SF6 for passivation at a processing pressure of 15 mTorr, Coil power 600-800W,  Platen power 100-150W, Bias voltage 50-100v (up to 200 peak-to-peak), Platen temp at 19 degrees, Lid temp 41 degrees.  Qual wafers are new bare Silicon.  Etch rates are normal and stable with 10+ years of data…. we just can’t complete the work due to failing seals.
> 
> Our chamber base pressure is between 1E-8 and 5E-8 Torr each morning.  When we put in a brand new seal and run only the LUR, it passes with 0.00 mTorr/minute leak rate.  That jumps to 3.00 mTorr/m after only 30 minutes of the SPTS recommended O2 Clean… then rises as time and more runs progress.  Wafers are coming out with black rings on their backsides. 
> 
> This should not be happening, and I believe it is due to incorrect material of the lip seals and o-rings.  I am pinging the network, though, to see if there might be a parameter change we need to effect that may assist us.
> 
> Have any of you seen this before?
> 
> Best regards,
> 
> Mark
> 
> 
> ________________________________________________________________
> 
> Mark Weiler
> Equipment & Facilites Manager
> Clair and John Bertucci Nanotechnology Laboratory
> Eden Hall Nanofabrication Cleanroom
> Carnegie Mellon University
> P:  412-268-2471
> http://www.nanofab.ece.cmu.edu
> 
> 
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