Comment stsetch SNF 2011-11-15 15:11:48: Unusual observations

When using the Al holder and a blank Si test wafer, I observed the following:
1. The backside He flow oscillates between 2.7 and 5.4 (not sure if the units are sccm).
2. During a 10 min O2 clean, plasma color changed from expected grey-blue to slightly purplish which suggests the presence of another gas.
I wiped off the bottom of the holder and the o-ring prior to use so a particle causing a He leak is unlikely.