1960: Epitaxial Deposition Process Enhances Transistor Performance

Development of thin-film crystal-growth process leads to transistors with high switching speeds.

In 1951 Gordon Teal and Howard Christensen at Bell Labs developed a process, now called epitaxial deposition, to grow a thin layer of material on a substrate that continues the underlying crystalline structure. Sheftal', Kokorish, and Krasilov described similar work on germanium and silicon in the U.S.S.R. in 1957.

At the urging of Ian Ross, a Bell Labs team led by Henry Theurer used chemical-vapor deposition to add a thin epitaxial layer of silicon between the base and collector of a transistor in 1960. This approach raised the transistor's breakdown voltage while dramatically increasing its switching speed, (1961 Milestone) two important circuit-design characteristics. The added manufacturing cost of the extra process step was more than offset by improvements in device performance. The technology was quickly transferred to Western Electric and used in manufacturing silicon transistors for electronic telephone switching in the Bell System.

Theurer gave a presentation on epitaxial transistors at the June 1960 Solid-State Device Research Conference that aroused widespread interest. Fairchild used epitaxy to fabricate the 2N914, one of its most successful transistors introduced in March 1961 and quickly emulated by Rheem, Sylvania, and Texas Instruments. Motorola applied the process to mass produce devices for automotive alternators. Epitaxial silicon also had an important impact on the manufacturing yield of early bipolar integrated circuits by allowing electrical isolation of the individual circuit components to be accomplished much more easily. It later found widespread application in the manufacture of MOS products. Epitaxial growth techniques are also used to form the ultra-thin layers common in compound-semiconductor manufacturing.

  • Christensen, H., and Teal, G., "Method of Fabricating Germanium Bodies," U. S. Patent No. 2,692,839, (Filed 7 April 1951. Issued 26 October 1954).
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  • Bassett, Ross Knox. To the Digital Age. (Baltimore, MD: Johns Hopkins University Press, 2002), pp. 25-28.