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Reducing Autodoping in Epitaxial Silicon

IP.com Disclosure Number: IPCOM000075672D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Fairfield, JM: AUTHOR [+3]

Abstract

In this method, autodoping at the interface between an epitaxial layer and the supporting substrate is minimized.

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Reducing Autodoping in Epitaxial Silicon

In this method, autodoping at the interface between an epitaxial layer and the supporting substrate is minimized.

A major problem in semiconductor device fabrication has been the autodoping of epitaxial silicon layers from diffused regions, normally subcollector regions. The surface concentration of the subcollector impurity is relatively high. When the epitaxial layer is deposited, the impurity gets redistributed in a normal and lateral direction over the interface. This effect is particularly pronounced when the impurity concentration on the surface is large. In the initial stages of the epitaxial process the subcollector impurity diffuses upward out of the substrate, doping the vapor stream and outwardly across the interface to produce unwanted doping at the interface.

In this method, the surface concentration of the buried subcollector region 10 in device 12 is maintained at a low value, as the epitaxial layer 14 is grown. This is accomplished by implanting region 10 by ion implantation below the surface of the substrate 12. When the epitaxial layer 14 is grown, the implanted region will diffuse in a direction parallel to the growth direction of the epitaxial layer. However, the impurity concentration, as shown in B, never reaches a significantly high value at the interface between substrate 12 and layer 14 to result in significant autodoping.

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