AGS - Service Notes

Service Note No: 02
To: RIE/CVD maintenance techs
Subject: Leak Checking Procedure on TSG/IPE-1000 systems with PC5000 controllers

Problem: A manual leak checking procedure is necessary in order to check the leak-up rate of the System 1000 vacuum chamber. This is due to the "single valve" design of the system which places the turbo pump as part of the chamber. Since the turbo also has a bearing purge, a large fixed leak is always present into the chamber.

Solution: The following procedure was developed to properly leak check the process chamber accurately.

PROCEDURE: (Start with chamber vented)

1. Turn off Turbo pump power.
   
2. Using the special KF10/16 adapter cap provided with the system, seal the turbo bearing inlet fitting located on the turbo pump above the oil sight glass.
   
3. In the manual mode, Press [MANUAL] + [ROUGH].
   
4. Allow the system to pump out for at least 5-15 minutes.
   
5. Press [MANUAL] + [ROUGH] again to seal the Rough valve.
   
6. Observe the pressure raise. Plot the leak up rate versus time over the next 5-15 minutes. The rate will initially be high but should level off at a constant value after initial outgassing.

   Figure 1: Leak Rate versus Time
   

7. The following values are representative of various degrees of leak rate for the System 1000:

   
    
   1mT/min	Excellent - Factory specification
    
   2mT/min	Good - usually after long pump-down
    
   5mT/min	Nominal - typical day to day rate
    
   10mT/min	High - leak possible - retry or check
    
   99mT/min	Gross - retry or call for service
    
   100mT/min	Out of range - call for service
    

   
   
8. When finished observation, press [MAN] + [VENT] to end.
   
9. Replace bearing purge line and restore power to Turbo.
   

Preventive maintenance: Wipe chamber seal daily. Check base pressure weekly, Check leak rate monthly, Perform a major PM at least once per year.

Note: Performing regular cleans and PM's keeps the system leak tight and clean.

Expert Tips: Vacuum systems always leak. The question is how much of a leak will actually interfere with the desired process. In general, ashing is forgiving and dielectric etching is more tolerant than metal or III-V etching processes. In PECVD the refractive index will change as a result of a leak.

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