[labnetwork] STS DRIE Multiplex Lip Seal failures

[Daniel Christensen]

Hi Mark,

My etch staff person is out of the office or he would jump on this.  He has been complaining about this to STS for a long time.

We too at the Univ of Wisconsin have experienced a change in the behavior of our ASE STS lip seals.  Our lip seals are for 100mm wafers. The change occurred a few (several?) years ago and is summarized below.  I don’t know what happened – if the seal vendor changed or the vendor had a material or manufacturing change but SOMETHING definitely changed.

SPTS should just release the design of the lip seals to us and allow us to go and qualify a new vendor.  The dang things cost >$200 apiece and sometimes don’t even last a dozen etches for us.


Before

  *   Lip seals delivered in a brown package
  *   Lip seals lasted
After

  *   Lip seals delivered in plastic
  *   Lip seals don’t last
  *   Lip seals can be “sticky” when first used.  We had to institute a VERY short plasma on the lip seals without wafers present to “un-sticky” them

We have always had the chamber orings degrade and when you wipe the used ones the wipe is super black.  we have always just changed them out when we open the chamber.  This has not changed when the lip seal behavior changed.  This isn’t as costly since we were able to determine the generic oring size.


That is our experience,
Dan Christensen
Univ of Wisconsin-Madison

From: labnetwork-bounces at mtl.mit.edu <labnetwork-bounces at mtl.mit.edu> On Behalf Of Mark Weiler
Sent: Tuesday, March 05, 2019 2:45 PM
To: Fab Network <labnetwork at mtl.mit.edu>
Subject: [labnetwork] STS DRIE Multiplex Lip Seal failures

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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