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Oral History – Arch Mohr
(Continued)
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Initial
contract effort was concentrated on the design and sample production of the
ge. types while silicon production processes were being developed in the
Somerville Advanced Dev. Group. The first process developed was used to
make the required pre-production samples. This process was considered not
very reproducible because of the difficulty in making the first samples. A
second process developed in Ad. Dev. by Loran Armstrong proved to be
superior to the 1st method and all subsequent samples needed to complete
the contract were made with this process. After completion of the
contract, RCA moved immediately into production of all 5 types. Two
transistor types that resulted from the contract were the 2N3054 and
2N3055. This silicon transistor process eventually became known as the RCA
"homotaxial" process. Geometry modifications of the silicon
"chip" led to a large number of announced silicon power
transistors.
Silicon
power transistors manufactured by the homotaxial process were very
competitive with other silicon transistors of that time. They had output
characteristics similar to ge. power transistors, and had the advantage of
higher temperature ratings. Marketing demands for these silicon units led
to the construction of the RCA Mountaintop, PA plant in 1960. I was named
production engineering manager of the new plant. At that point my career
changed from design & development engineering to production management
which lasted until I retired in 1981.
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Oral History – Arch Mohr
(Continued)
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I would
like to mention some of the manufacturing improvements that occurred in the
20 years I was involved in manufacturing. Our initial silicon transistors
were made from 3/4 inch wafers. When I retired, 4 inch wafers were in
production. The Mountaintop plant (now Intersil) has 8 inch capability.
Diffusion furnaces had only on-off controllers and very limited constant
temperature zone. Furnaces now have proportional controllers with long
constant temp. zone. Geometry chip patterns on our first transistors were
made by a silk screen process. Photolithography and photo resist
techniques are now used with much improved tolerances. While I was still
with RCA, these improvements along with process improvements, reduced the
cost of the active chip to the point that packaging (case) became a
significant part of the total cost of the transistor. This led to the
development of other packaging designs including the RCA
"versawatt" package.
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