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Enhanced Diffusion in Porous Silicon

IP.com Disclosure Number: IPCOM000082271D
Original Publication Date: 1974-Nov-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

Poponiak, MR: AUTHOR [+2]

Abstract

In this method, porous silicon formed by electrolytic etching-in a concentrated HF solution, is used to introduce semiconductor impurities into a semiconductor body to a greater depth than otherwise possible.

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Enhanced Diffusion in Porous Silicon

In this method, porous silicon formed by electrolytic etching-in a concentrated HF solution, is used to introduce semiconductor impurities into a semiconductor body to a greater depth than otherwise possible.

Diffusion of a semriconductor impurity into a monocrystalline semiconductor body is a high-temperature process. In order to obtain deep diffused regions, exposure of the device to high temperatures for long periods of time is necessary. This long exposure is frequently detrimental to the device structure.

In the method illustrated in Fig. 1, a lateral PNP transistor is fabricated. In the method, a masking layer 10, typically Si(3)N(4) or a composite layer utilizing Si(3)N(4), is deposited on the surface of monocrystalline body 12 and etched using photolithographic and subtractive etching techniques. Body 12 is electrolytically etched in a concentrated HF solution, which results in forming porous silicon regions 14 in the body in the unmasked regions of the body.

The porous silicon resulting from the etching process is composed of the original silicon lattice, with roughly cylindrical pores of large length relative to their diameter. A suitable P-type dopant is then introduced into regions 14, where they are quickly transported through the pores to the interface between regions 14 and the monocrystalline portion of body 12. Further heating causes the semiconductor impurity to diffuse into the monocrystalline regions of bod...