[labnetwork] Silicon Nitride question

[Paolini, Steven]

Rick, Silicon nitride via LPCVD is an extremely dirty process from the perspective of the vacuum pump. In my experience, I have had the most success with this approach;  heat the pumping line from where the transition from quartz to steel is and continue with heat trace up to a liquid cooled trap. This method actually enhances the growth of by-products (mainly ammonium chloride) in an area that can be easily serviced. When I was in manufacturing and we ran these furnaces constantly, this configuration along with a spare water cooled trap, significantly reduced downtime since we controlled where the by-products collected. Here at Harvard we simply use a stainless mesh filter on the pumping line and service the transitional fitting that connects to the quartzware every few months but we don't run nearly as much as a production facility.
I am unfamiliar with adding hydrogen to LPCVD nitride, just DCS and NH3. I would choose a pyrolizing type scrubber for any excess SIH4 and if there was added H2 it would mitigate that as well.
Regards,
           Steve Paolini
          Harvard University CNS

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Morrison, Richard H., Jr.
Sent: Wednesday, April 11, 2012 8:09 AM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] Silicon Nitride question

Hi Everyone,

I am restarting a Silicon Nitride LPCVD process and I have a few questions. The process will use a EBARA dry pump therefore should I use a trap on the vacuum pump inlet to catch any particulate generated?

Any issue with excess hydrogen from the process going into the dry pump, do I need a burn box on the vacuum pump exhaust?

2nd question has anybody tried to run the LPCVD process on a wafer with a platinum metal pattern on the surface? I was wondering if there maybe some adverse effect because of the catalytic nature of Platinum.

Thanks
Rick


Rick Morrison
Senior Member Technical  Staff
Group Leader Microfabrication Operations
Draper Laboratory
555 Technology Square
Cambridge, MA  02139

W  617-258-3420
C   508-930-3461

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