Problem AG4108 SNF 2009-10-08 11:14:16: Needs process qualification

shott at snf.stanford.edu shott at snf.stanford.edu
Fri Oct 9 05:51:38 PDT 2009


Following work by Mike and Elmer to purge out the cooling lines and then get the pyrometer back in shape, I ran a full cassette of wafers using the 1150QUAL run.
The first bit of good news is that I was able to run all 25 wafers without any interlock problem or "Top Plate Errors".  As we now have a separate K-type thermocouple affixed to the top plate, I was able to monitor the temperature of the plate for each wafer and to note both the minimum temperature (that occurs just as the lamp come on) and the maximum temperature that occurs just a couple of seconds after the lamps go out.
After the first 3-4 wafers while the system is still warming up, the minimum top plate temperature was observed to be fairly repeatable between about 31.9 C and 32.6 C .... in fact, most of the wafers reached 31.2C +/- 0.2C.  The maximum temperature also seemed fairly tightly distributed in the range of 42.4 C to 43.7 C.  This seems pretty significantly better than we have observed recently .... and 11 C increase in temperature during the run seems quite acceptable as the overtemp switches are set to trip at about 65 C.
A couple of other relevant facts.  The supply and return coolant pressures were 72 and 40 PSI, respectively and the coolant flow was measured to be 1.8 GPM (measured by the big plexiglass flowmeter in the fingerwall).  During these runs the average lamp intensity to reach 1150 degree C was about 41%.
I'm going to clear this problem in terms of cooling .... but submit another one related to an apparently thin oxide.
John




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