Browse Prior Art Database

Prevention of Autodoping During Silicon Epitaxial Deposition

IP.com Disclosure Number: IPCOM000088895D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Fleming, DJ: AUTHOR [+3]

Abstract

A process is disclosed for preventing lateral and vertical autodoping during silicon epitaxial deposition which provides a self-aligned epitaxial silicon outdiffusion cap over previously diffused structures in the semiconductor substrate. These caps also serve to delineate alignment targets for post-epitaxial processing.

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Prevention of Autodoping During Silicon Epitaxial Deposition

A process is disclosed for preventing lateral and vertical autodoping during silicon epitaxial deposition which provides a self-aligned epitaxial silicon outdiffusion cap over previously diffused structures in the semiconductor substrate. These caps also serve to delineate alignment targets for post-epitaxial processing.

Figs. 1-4 illustrate the steps. In Fig. 1, the silicon substrate 1 has formed thereover a silicon dioxide masking layer 2, and the windows 3 are opened therein to permit the diffusion of the N+ diffused region 4 into the P- type substrate 1 (and in like manner for P+ diffused regions in N- substrates, etc.).

In Fig. 2, the silicon dioxide mask 2 is retained to enable the formation of a self-aligned epitaxial layer 5 over the diffused region 4; which will serve as an outdiffusion preventive cap.

In Fig. 3, the composite layers of silicon dioxide 2 and polycrystalline silicon 6 formed thereover during the preceding epitaxial deposition step have been removed by stripping in hydrofluoric acid which removes the oxide masking layer 2 and permits the "lift-off" of the polycrystalline silicon layer 6. The oxide layer 2 is etched through the polysilicon layer 6 by virtue of the porous nature of the polysilicon layer 6 and/or the discontinuous nature of the polysilicon-epitaxial silicon boundary which allow the hydrofluoric acid to seep through to enable the etching of the underlying oxide layer 2. Fig. 3 illustrates the condition of the substrate after the oxide layer 2 has been etched and the polysilicon layer 6 ha...