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Browse Prior Art Database

Solid Arsenic Diffusion Source for Silicon

IP.com Disclosure Number: IPCOM000077977D
Original Publication Date: 1972-Oct-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Beyer, KD: AUTHOR

Abstract

In diffusing arsenic into a silicon substrate from a solid source deposited on the substrate, such as an arsenic doped glassy layer, difficulty has been experienced in producing diffused regions having high-surface concentrations. One approach in the art towards the solution of this problem is to conduct the diffusion from this solid source in the presence of oxygen. The oxygen may be provided by an oxygen ambient or by a thin silicon dioxide layer between the arsenic doped source and the substrate which is being diffused into. However, the presence of this oxygen provides for conditions which are favorable to undesirable formation of Beta-cristobalite crystals in the solid arsenic source.

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Solid Arsenic Diffusion Source for Silicon

In diffusing arsenic into a silicon substrate from a solid source deposited on the substrate, such as an arsenic doped glassy layer, difficulty has been experienced in producing diffused regions having high-surface concentrations. One approach in the art towards the solution of this problem is to conduct the diffusion from this solid source in the presence of oxygen. The oxygen may be provided by an oxygen ambient or by a thin silicon dioxide layer between the arsenic doped source and the substrate which is being diffused into. However, the presence of this oxygen provides for conditions which are favorable to undesirable formation of Beta-cristobalite crystals in the solid arsenic source.

The present process provides for high-arsenic concentrations in the substrate without any undesirable Beta-cristobalite formation. In the present structure, a thin layer of silicon dioxide 10 having a low concentration of arsenic is deposited on the diffusion surface. A layer of silicon dioxide 11 having a much higher arsenic impurity concentration is deposited over layer 10. The structure is then heated to an appropriate temperature in an inert atmosphere, e.g., nitrogen, to form diffusion region 12.

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