Planar transistor

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A planar transistor is a type of transistor named after its manufacturing technique . This design was first presented in 1959 by Jean Hoerni (employee of Fairchild ) for a bipolar transistor , in the same year patents were submitted for the transistor and the manufacturing technique , the planar process .

Simplified sectional view of a planar transistor

In planar transistors, all electrically active areas (collector C, base B and emitter E) are located close to the surface inside a flat semiconductor crystal (the prototype already used silicon ). Already during the production of the different doped areas by diffusion , these electrically sensitive areas are protected by a superficial oxide ( silicon dioxide ) (a discovery that goes back to Martin M. Atalla ). In contrast to mesa transistors - the design of bipolar transistors customary up to that time - this oxide was not removed after diffusion, so that the pn junctions , which largely ran in the semiconductor substrate, continued to be protected by the oxide on the surface. In this way, negative external influences could be greatly reduced, e.g. B. Impurities on the surface that can cause leakage currents. In addition, planar transistors are significantly less sensitive to mechanical stress, as Hoerni demonstrated with a test in 1959.

The first planar transistor was a planar diffusion transistor variant of the Fairchild 2N696 (actually a mesa transistor) in 1960. It was followed by 2N1613, the first "true" planar transistor. Due to the significantly improved electrical properties compared to other designs, the planar transistor quickly gained acceptance and also opened the way to the commercial use of integrated circuits (ICs, "microchips"), in which complex transistor circuits are manufactured on a single-crystal substrate ( wafers ). Instead of bipolar transistors, however, mainly insulating-layer field effect transistors (IGFET) are used, the main representative of which is the well-known metal-oxide-semiconductor field-effect transistor (MOSFET). These transistors are also manufactured in the form that is still common today as planar transistors, although the doping usually takes place via ion implantation . With newer technology nodes below the 20 nm technology, however, other designs such as the FinFET are also used.

Individual evidence

  1. ^ A b Christophe Lécuyer, David C. Brock: Makers of the Microchip: A Documentary History of Fairchild Semiconductor . MIT Press, 2002, ISBN 0-262-01424-6 , pp. 30th ff .
  2. ↑ Patent US3025589 : Method of Manufacturing Semiconductor Devices. Registered on May 1, 1959 , inventor: JA Hoerni. ‌
  3. ↑ Patent US3064167 : Semiconductor device. Registered on May 15, 1960 , inventor: JA Hoerni. ‌
  4. ^ Bo Lojek: History of Semiconductor Engineering . Springer, 2007, ISBN 978-3-540-34258-8 , pp. 125 f .
  5. ↑ Fairchild 2N1613 Early Silicon Planar Transistor. In: Transistor Museum Photo Gallery. Retrieved June 23, 2014 .
  6. ^ Peter Robin Morris: A history of the world semiconductor industry . IET, 1990, ISBN 0-86341-227-0 , pp. 37 ff .