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Epitaxial Isolation and Device Fabrication

IP.com Disclosure Number: IPCOM000073826D
Original Publication Date: 1971-Feb-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Shepard, JF: AUTHOR [+2]

Abstract

When growing epitaxial P-type layers on P-type substrates which contain N+ (arsenic or phosphorus doped) buried regions, a phenomenon characterized as the epitaxial spike effect has been observed. Using arsenic as a diffusant, a structure similar to that shown in A is obtained. The lateral spiked N regions are extremely flat and can extend laterally as much as 50 mils to either side of the original diffusion. The lateral extent and thickness of the spike depends on deposition conditions such as doping concentration and spikes typically observed are about 0.5 micron in thickness.

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Epitaxial Isolation and Device Fabrication

When growing epitaxial P-type layers on P-type substrates which contain N+ (arsenic or phosphorus doped) buried regions, a phenomenon characterized as the epitaxial spike effect has been observed. Using arsenic as a diffusant, a structure similar to that shown in A is obtained. The lateral spiked N regions are extremely flat and can extend laterally as much as 50 mils to either side of the original diffusion. The lateral extent and thickness of the spike depends on deposition conditions such as doping concentration and spikes typically observed are about 0.5 micron in thickness.

The N-doped regions of drawing A can be made to extend to the surface of the epitaxial layer if phosphorus which has a higher diffusion coefficient is used as the dopant. The resulting structure is similar to that shown in B.

Advantage may be taken of this spiking phenomenon to accomplish the isolation of pockets of one conductivity type surrounded by regions of opposite conductivity type. Thus, C shows a structure in which isolated pockets of P conductivity type semiconductor material are obtained using a single epitaxial deposition step and a single diffusion step. This structure can be achieved if the N conductivity type buried diffused regions are positioned such that the N-type regions extend to the surface of the epitaxial layer and such that the laterally growing spikes of N-type material intersect.

Using the phenomenon in a manner similar to that shown in D an N-channel junction FET can be fabri...