Comment epi2 SNF 2007-05-17 10:20:39: Dome/Etch info

maurice at maurice at
Thu May 17 10:20:39 PDT 2007

The Dome (the top of the deposition chamber) was removed, acid cleaned  and reinstalled yesterday.  The system was baked and purged overnight.  The system was leak checked this morning with a leak rate of 1.4 mT/min. This incident  put the system down for more than a day.
We will be inspecting the dome each working day (monday-friday) in the morning until further notice.  The system  will be shutdown if we see deposition on the dome.  This is to keep the system from imploding.
The length of all etch steps in the etch recipes has been tripled.
We were surprised to see that the dome was coated since all users should be doing relativity thin layers.  So either our etch recipes are not sufficient or users are growing layers thicker than they are admitting to depositing or users are using the wrong etch program. So:
Etch after each processed wafer.
If you are depositing Ge or SiGe with high Ge content then you must use the Ge etch recipe after each wafer.  The Ge etch recipe is a low temp etch that will remove Ge.  The other high temp etch recipe will cause the Ge to coat the dome.
If you are doing thick SiGe or Ge deposition, come talk to me.  Will will have to create a special etch recipe.
The max Si deposition is 3um.

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