Changes to base pressure

Eric Perozziello eap at gloworm.Stanford.EDU
Wed Aug 13 18:32:58 PDT 2008

I agree that the absolute base pressure is not essential for an
oxide etch, but I'm afraid that the failure to reach the "usual" base
pressure is really a symptom of a large leak rate.  On a few occasions,
I measured that rate, and it was unacceptably high (which I think
I noted in coral).

Given the relaxation in the programmed base pressure, can we have
regular leakup rates measured and logged somewhere?  And yellow-light
the machine if it exceeds 5 or 10 mT/min?


On Wed, 13 Aug 2008, Nancy Latta wrote:

> Hello Everyone,
> One of the things to come out of the Etch Quality Circle is a better
> understanding of why the base pressure for the tool had been set to
> 0.5mT.  It seems that when to etcher was purchased it was configured for
> metal etching.  It was never used as a metal etching tool, however.
> A major concern with metal etching is moisture and pumping down to very
> low base pressures assured moisture-free etching.  We really do not need
> to pump down to 0.5mT for the processes we run in the amtetcher.
> I have changed all the standard recipes (1,2,3,4,5 and 7) and their
> back-up recipes (11,12,13,14,15 and 17) to have a base pressure of
> 0.8mT.  I have also reflected that change on the newly laminated Recipes
> and Etch Rates Sheet in the logbook.
> This should put an end to the annoyingly long pump downs we have
> recently been experiencing and bring peace back to Etchland.
> All comments welcome,
> -Nancy

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