EARLY TRANSISTOR HISTORY AT

TEXAS INSTRUMENTS 

Mary Anne Potter

 

Oral History – Mary Anne Potter

(Continued)

 

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.   

    

 

Oral History – Mary Anne Potter

(Continued)

 

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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