Arcing Problem Update for AMT etcher

[Jim McVittie]

AMT Users,

I was asked today about what we are doing about the arcing problem. Here
is my latest thinking:

   *  I expect that the cause is a hardware problem which we have not
     been able to identify.
   * The likely mechanism is a hollow cathode induced currect filement
     from the plasma to bare metal regions on the cathode/hexode.
   * A possible solution is to reduce the pressure. A lower pressure
     will increase the sheath thicknes and thus should reduce the hollow
     cathode effect. Elmer has done some tests which indeed show that
     arcing increases at higher pressure.
   * Nancy has done some etch rate tests for program #3 at 40, 45 and 50
     mT.  The results are as follows:

      Pressure         C          T          B          R
L          Avr
       50mT            318      324       306       313      306
313.4
       45mT            324      329       310       320      315
319.6
       40mT            370      376       353       360      356
363.0

         So it looks like we can go down in pressure to reduce the
arcing and actually get an          increase in etch rate. I was
surprized with the results in that I expected a decrease in etch rate
with pressure.

I am now looking for a volunteer to test program #3 at 40 mT on
patterned wafers.

    Thanks,  Jim
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