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Fabricating Pedestal Transistor

IP.com Disclosure Number: IPCOM000074814D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Kleinfelder, WJ: AUTHOR [+2]

Abstract

The use of high-energy ion implantation of the pedestal subcollector is used as a means to, (1) reduce the processing steps necessary to form a pedestal transistor by eliminating the necessity of growing a second epitaxial layer, (2) reducing the tolerance required in the control of epitaxial layer thickness, and (3) ensuring automatic alignment of the pedestal and emitter structure during fabrication. An example of the processing sequence is as follows: 1) Oxidize initial P- wafer; 2) Etch conventional subcollector opening; 3) Diffuse N subcollector; 4) Reoxidize wafer; 5) Etch conventional isolation opening; 6) Diffuse P isolation regions; 7) Remove all oxide and grow epitaxy layer;, 8) Oxidize wafer to produce the Fig.

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Fabricating Pedestal Transistor

The use of high-energy ion implantation of the pedestal subcollector is used as a means to, (1) reduce the processing steps necessary to form a pedestal transistor by eliminating the necessity of growing a second epitaxial layer, (2) reducing the tolerance required in the control of epitaxial layer thickness, and (3) ensuring automatic alignment of the pedestal and emitter structure during fabrication. An example of the processing sequence is as follows: 1) Oxidize initial P- wafer; 2) Etch conventional subcollector opening; 3) Diffuse N subcollector; 4) Reoxidize wafer; 5) Etch conventional isolation opening; 6) Diffuse P isolation regions; 7) Remove all oxide and grow epitaxy layer;, 8) Oxidize wafer to produce the Fig. 1 structure; 9) Open conventional reach- through area for collector and resistor areas; 10) Diffuse N reach-through and resistors;, 11) Reoxidize wafer; 12) Etch conventional base and isolation openings; 13) Diffuse P base region to produce the Fig. 2 structure; 14) Reoxidize wafer and deposit pyrolytic oxide layer 10 over the thermal oxide layer 12;, 15) Deposit beam stop mask 14. This could be a metal evaporated film such as gold, aluminum or chromium or a thick layer of photoresist. The characteristics of this film must be such that it will be capable of absorbing the ions which will be used to implant the pedestal (about 1.5 MeV P(31)+ ions) and must be resistant to hydrofluoric acid attack. Chromium and photo...