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Processing Transparent Substrates in the VersaLine Systems

The PlasmaTherm VersaLine systems rely on a wafer sensor in the load lock that makes processing transparent wafers particularly challenging. Here is a procedure to safely work around the sensor.



Processing Transparent Wafers in the VersaLine Tools (hdpcvd, PT-OX and PT-MTL)



Processing transparent wafers (quartz, pyrex or glass) in the PlasmaTherm VersaLine tools may present challenges in the transportation of the wafers.  The load lock wafer sensor does not ‘see’ the wafer and must be tricked into loading the sample.  In doing this, the tool then assumes two wafers are present.  The following procedure describes how to overcome this situation.


A couple of things to consider; to avoid having to 'trick' the tool wafers can have a metal coating on the backside of the wafer.  That way the sensor will pick up the wafer.  Also, wafers that are not backside polished may not exhibit the transparency problem.  The rough back side scatters enough light to sense a wafer is on the loading arm.



  • Vent the load lock.
  • Place a dummy Si wafer over the sensor.  As you look into the load lock there will be a red light.  That is the sensor.
  • Load the wafer to be processed onto the loading arm.
  • Pump the load lock.
  • Start the Job. At this point there will be a wafer shown in the load lock and another shown in the chamber.
  • When the job is completed the tool will be confused and not unload the wafer.  You will need to delete the load lock wafer.
  • Click on the Maintenance button.
  • Go to Mode and put the tool from Production into Maintenance.
  • Click on Transport and click on the AL (load lock) area.  It will highlight in pink.
  • Click on Edit Material.  Click on Delete Material and Accept on the right hand side of the screen.
  • Go back to the Transport screen and verify the wafer that was in the load lock is gone.
  • Go to Mode and put the system back into Production.  The wafer should unload.
  • You may need to vent the load lock even if ‘Vent after job’ has been selected.

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