[labnetwork] STS DRIE Multiplex Lip Seal failures

Wed Mar 6 11:08:43 EST 2019

Keep in mind that the HeLUR is an overall pressure indicator.  Your lip seal may be fine and your chamber may be leaking elsewhere.  We have run into the same problem and have been performing an helium leak check.  The lid seal could be a culprit, too.

Also, make sure that your VAT gate valve door is holding good vacuum by checking your chamber pressure.  If it goes up when the load lock is open then the gate valve door may be suspect.

Cheers!

Julia Aebersold, Ph.D.

MNTC Cleanroom Manager

University of Louisville

2210 South Brook Street

Shumaker Research Building, Room 233

Louisville, KY  40292

(502) 852-1572

http://louisville.edu/micronano/<http://louisville.edu/micronano>

________________________________
From: labnetwork-bounces at mtl.mit.edu <labnetwork-bounces at mtl.mit.edu> on behalf of N P VAMSI KRISHNA <vamsinittala at gmail.com>
Sent: Tuesday, March 5, 2019 8:25:38 PM
To: Mark Weiler
Cc: Fab Network
Subject: Re: [labnetwork] STS DRIE Multiplex Lip Seal failures

Hi Mark Weiler,
In my experience, the chamber O-rings should be Kalrez O-Rings, which can withstand very high temperatures (white color O-ring). I request you to check once if SPTS is supplying you the right one.
Please check all the 4 chamber heaters (inner wall, chamber, and others) and confirm if the temperatures (~120 deg C) and the respective voltages are within the spec. Maybe one of the heaters is getting a higher voltage.

Hope this helps.

Thanks and best regards,
vamsi

On Wed, Mar 6, 2019 at 6:11 AM Mark Weiler <mweiler at andrew.cmu.edu<mailto:mweiler at andrew.cmu.edu>> wrote:
Correction...

In my haste to write something up and get out the door I mixed up the gas is in the problem description.

Our process is typical Bosch SF6 and  O2 for etching .... switching off with C4F8 for passivation...

Mark

Mark Weiler
Equipment & Facilities Manager
Claire and John Bertucci Nanotechnology Laboratory
Electrical and Computer Engineering | Carnegie Mellon University
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On Mar 5, 2019, at 18:42, Mark Weiler <mweiler at andrew.cmu.edu<mailto: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
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--
--
Thanks & Best Regards,
-----------------
N.P.Vamsi Krishna
3D Heterogeneous Integration and System Scaling Lab,
Center for Nano Science and Engineering (CeNSE),
Indian Institute of Science(IISc), Bangalore.
INDIA-560012
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