Have you ever wondered about where that microprocessor in your computer came from, historically speaking? It has a quite respectable pedigree. In this first article in a two-part series, an IBM chip designer with 30 years in the field traces the chip from WW II through Moore's Law.
In the Beginning
Back in the days when vacuum tubes ruled the electronics world, researchers at Bell Labs like William Shockley were investigating the properties of various semiconductor materials including germanium and silicon. During World War II, radar receivers needed diodes responsive enough to act as frequency mixer elements at microwave frequencies. Traditional vacuum tube diodes did not respond fast enough, so solid state diodes were used instead.
After the war, research continued and on December 22, 1947 William Shockley, John Bardeen, and Walter Brattain built the first practical point-contact "transistor" (a name proposed by John R. Pierce and chosen by internal ballot). Shockley, Bardeen, and Brattain received the Nobel Prize in Physics in 1956 for their contribution, well after the Western Electric subsidiary of the Bell system put the transistor into production internally, while Bell also licensed the invention to other companies.
Starting with low power, low frequency applications like the ubiquitous "cheap Japanese transistor radio," transistors gradually began to replace vacuum tubes. As transistors improved and as circuit designers became familiar with how to use these new devices, vacuum tubes were relegated to a very few specialized applications. Solid state television/monitor screens are only today in the process of replacing the venerable color TV tube.
There were eventually two major types of transistors that went into commercial production. The first was the bipolar junction transistor (BJT) whose three leads were identified as base, collector, and emitter. The relatively small current through the base lead was used to control the flow of current between the collector and the emitter. The BJT is either PNP or NPN depending on how the three regions of the transistor were "doped" with impurities to create extra free electrons (N region) or "holes" (P region) where electrons were missing from the silicon crystal structure.
The second type was the field effect transistor (FET) where voltage applied to the gate pin of the device is separated from the semiconductor channel between source and drain by a thin insulator layer (in the insulated gate FET) or a diode junction (in the junction FET). This gate voltage creates an electric field in the channel used to control current flow through the channel between the source and drain pins of the transistor.
The first successful attempts to create an integrated circuit were made independently by Jack Kilby working at Texas Instruments and Robert Noyce working at Fairchild Semiconductor. Kilby started work on a germanium integrated circuit in July of 1958 and filed for a patent on this on February 6, 1959. Noyce's efforts using silicon instead of germanium were about six months behind Kilby's, but resulted in a more complex "unitary circuit" for which a patent was issued April 25, 1961.
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