HEPA air reduction in off-hours
rcrane at snf.stanford.edu
Thu Oct 6 13:54:49 PDT 2005
HEPA air flow will be reduced during off-hours starting 10/17/05.
I wish to announce a change in facilities operation concerning air flow
through the HEPA filters during off-hours as an energy cost reduction
measure. We followed a similar procedure during the '80s and 90's. About
eight years ago changes in the control system caused us to stop the
reductions. The plan is to reduce HEPA air flow by 50% from 2300 to 0700
MTWThF and all day Saturday and Sunday. Exhaust air flow will not be
affected. This change will implemented starting Monday evening, 10/17/05.
Discussion: Even though this procedure has been followed in the past,
we have recently measured particle counts at full HEPA air flow during
the day and at 50% flow during the night. The particle counts were very
similar throughout the cleanroom. In both cases the cleanroom qualified
as a class 100 facility in litho, etch, and diffusion aisles as
expected. The thin film and epi aisles qualified as class 1000 as
expected. What will change is the cleanroom's ability to recover quickly
from a particle assault. Given the low number of fab users during these
off-hours, this should be a not a problem. Energy cost saving is
projected to be $7k-$10k/year.
Thanks for your cooperation,
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