United States Patent 3,489,622
January 13, 1970

Method Of Making High Frequency Transistors
Fred Barson
Vir A. Dhaka

Filed May 18, 1967
Image of US PATENT 3,489,622

Abstract of the Disclosure

A method of making transistors useful for high frequency applications by forming on the surface of a semiconductor substrate of a first conductivity type a silicon dioxide layer doped with a conductivity determining impurity of opposite type. The doped layer covers only the portions of the surface corresponding to the selected extrinsic base area of the transistor; the intermediate portion of the surface corresponding to the selected intrinsic base area is left uncovered. The extrinsic base is formed by diffusion from the doped layer and the intrinsic base and emitter are formed by diffusion through the intermediate uncovered area.
Figure descriptions: cover graphic

  • Figures 1 through 7 are cross-sectional views diagrammatically illustrating the steps to be followed in the fabrication of a transistor in accordance with a preferred embodiment of the present invention.

 Citations [54]:
3,312,881 04/1967 Yu 3,389,023 06/1968
National Museum of American History
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