Problem stsetch 2002-11-17 11:12:26: helium cooling pressure fluctrates

quickwin at quickwin at
Sun Nov 17 11:12:27 PST 2002

I tried etching two different wafers but always get this fluctration in helium cooling pressure (from 9.84 to 10.03). It is not suitable for my wafer so I had to cancel all my timeslots on Sunday.
I suspect it is caused by the organic junk on the back of the aluminum wafer holder. The material looks like wax but can not be removed with acetone. When I pulled my wafers out from the machine, I see chunks of this material on the back of my wafer. The machine might need to be opened and cleaned?
In addition, nobody recorded entry of machine log from Friday to Sunday (Nancy was the last user who entered into the machine logbook).

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