United States Patent 3,465,215
September 2, 1969

Process For Fabricating Monolithic Circuits Having Matched Complementary Transistors And Product
Ralph O. Bohannon Jr.
Robert A. Stehlin

Filed June 30, 1967
Image of US PATENT 3,465,215

Abstract of the Disclosure

A process for fabricating a monolithic circuit having a matched pair of complementary transistors, a diffused resistor, and a diode. The starting material is a p-type substrate having heavily doped n-type diffused regions buried under an n-type epitaxial layer at each position where a transistor is to be formed. First a p-type diffusion is made to form the collector of the PNP transistor and an isolation ring around each burried n-type diffused region. The p-type diffusion is made to a depth sufficient to penetrate through the epitaxial layer to the p-type substrate to form isolation rings. However, where a PNP transistor is to be formed, the buried n-type region isolates the p-type collector region from the p-type substrate. Then a first n-type diffusion forms the base of the PNP transistor, and a second p-type diffusion forms the base of the NPN transistor, the resistors, and the anode of the diode. A third p-type diffusion forms the emitter of the PNP transistor, and finally a second n-type diffusion forms the emitter of the NPN transistor.
Figure descriptions: cover graphic

  • Figure 1 is a schematic sectional view illustrating a monolithic circuit constructed in accordance with the present invention.
  • Figures 2-6 are schematic sectional views similar to Figure 1 illustrating successive steps in the process for fabricating the monolithic circuit of Figure 1.

 Citations [54]:
3,327,182 06/1967 Kisinko 3,370,995 02/1968 Lowery
National Museum of American History
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