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Oral History – Mary Anne Potter
(Continued)
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I learned from the techs how to
perform all of the diffusion processes and associated cleanups myself. I
also learned to do the electrical testing to evaluate diffusions using the
curve tracer. One technique I did not ever master was the lap and stain one
in which diffused pilots were put on a beveled stem, lapped and polished,
then stained and inspected using sodium light to count the fringes. From
the fringe count and the bevel angle, a diffusion depth could be
calculated.
The lab consisted of eight
globar furnaces, in stacks of two, along one wall. The control panel for
these furnaces was against the back wall. Also along the back wall was a
fume hood that was used to clean diffusion tubes and could also be used as
a backup for cleaning the silicon slices. Across from that hood was another
all-purpose fume hood where the extremely important lap and stain equipment
was set up. Next to this hood was a table where hot diffusion boats could
be unloaded. Behind this hood and table were another table and the fume
hood with the most exhaust where extremely hot sulfuric acid was maintained
for slice cleaning. The monitoring equipment for diffusions was on a table
near the front entrance to the lab. As I recall, we had a resistivity test
set to measure material conductance and diffusion sheet resistance and a
curve tracer to measure the transistor characteristics of the diffusions.
We also had a gauge for measuring slice thickness. A cart held the
potentiometer that was needed to measure the temperature of the diffusion
furnaces in their heat zones.
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Oral History – Mary Anne Potter
(Continued)
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The pilot line techs delighted
in breaking in “their” new engineer. One day about mid-morning, they all
left for break at the same time and asked me to keep an eye on things and
listen for buzzers. Nothing should need to be pulled before they got back,
according to them. A few minutes after they left, an explosion occurred at
the back of one of the furnaces. When the techs returned from break, I was
under the table farthest from the furnaces. Only then did I find that they
had played a joke on me; they knew the red phosphorus source would explode
because it always did. They also knew that I had not been around when they
had done one of these diffusions. I’m surprised they didn’t photograph my
reaction. The techs who worked full-time in the lab were great teachers.
Two of them became good friends of mine. Shortly after I became useful
(rather than totally inept) in the lab, a task force was formed to try to
find out why the yields were low on the production line. I was the engineer
designated to be the liaison between diffusion production and process/product
engineering. This meant that I needed to be at work nearly all the time
because production diffusion was a 3-shift operation. I spent many a night
working with the QC inspector as she showed me all of her observed defects
that may or may not relate to yield problems.
My work schedule went like
this: Sunday night I'd be at work for 3rd shift starting at
about 11 PM. I would meet with 1st shift
Potter
Oral History, Page 4
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