Humidity control alert

Dick Crane rcrane at
Fri Mar 19 08:25:28 PST 2004

Lab users,

Our ability to control humidity in the litho area will be compromised
starting March 22 and continue to be a possible problem for the next
four weeks. If we have high humidity days, then the humidity in the
litho area could rise above the 45% set point level. This loss of
control may disrupt some photoresist processes. We will have normal
humidity control in litho through 0600 on March 22 and marginal control

Why is this happening? Cardinal CoGen, who operates the 60MW cogen plant
for Stanford, is doing a major cooling tower upgrade. The CIS building
is the only external user of the cooling tower. While the cogen plant
has built in redundancies for its steam/electric circuits, CIS, as a
parasitic load, operates only on one cooling tower and hence, has no
back up.

Why did we not know of the shutdown earlier? Our building services such
as heating and cooling are provided by Facilities and Operations
(FacOps). Although the shutdown has been schedule well in advance,
FacOps wasn't notified until a few days ago.

What are we going to do? FacOps will attempt to maintain control by
creative measures with the air conditioning units. This should work
unless the outside humidity is too high. I will be working with FacOps
to obtain a portable chiller/heat exchange to be placed in the receiving
area to supply the dehumidifier circuit. Shutting down the dehumidifier
without backup plans is simply unacceptable.

I keep you post as to progress made and I'm sorry for the inconvenience,


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