Comment tylansige SNF 2004-07-21 17:48:26: temperature and pressure stabilization problem

rohits at rohits at
Wed Jul 21 17:48:27 PDT 2004

The temperature does not stabilize at 500C even after waiting for 1 hour. There is about 5C variation from the front to the back of the tube. There is also a temporal variation in each zone. For the center zone, it fluctuates from 497-501.5 with a period of about 5 min. 
Also, the bleed valve (nupro?) for manual control of N2 backflow doesn't seem to be able to turn off N2 backflow completely even when turned fully clockwise. There is still 128sccm of flow. This results in a minimum pressure of 168mtorr while flowing 76sccm SiH4 and 16sccm GeH4. In the past, this used to yield the target pressure of 100mTorr with these gas flows.

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