Problem drytek2 SNF 2009-09-07 09:02:54: Pressure

shott at snf.stanford.edu shott at snf.stanford.edu
Fri Sep 11 23:09:29 PDT 2009


We have replaced the pump and the capacitance manometer.
The manometer is a newer MKS Model 627 1 Torr head rather than the older Model 227 that was in service previously.  We have a custom wiring harness to adapte the existing controller to the new head.
This head should produce 0-10 output for a pressure of 0-1 torr.  In other words, 150 mTorr should produce 1.5 V output.
For a time, we though that we had a blower problem becauase the "normal" nitrogen flow conditions was reading (it appeared) about a 10X higher pressure than normal .... that is 3400 rather than 340 mTorr.  However, a 1 Torr head CAN'T read 3400 mTorr (because that would be an output of 34 V which can't happen for a head supplied by +/- 15 V.
As a result, I believe that this was actually reading 340.0 Torr and we had failed to set the decimal point.
Also, because this is a 1 Torr head (Drytek1 uses a 10 Torr head), we need the inputy voltage on teh Type 252A pressure controller to be set to
10V input rather than 1 V input.
We will confirm these things on Monday with test wafers and with more careful pressure and voltage measurements.
Please process with caution until that determination has been made.
Thanks,
John




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