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Tailoring Impurity Profiles

IP.com Disclosure Number: IPCOM000092241D
Original Publication Date: 1968-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Hu, SM: AUTHOR [+2]

Abstract

This technique forms preselected impurity profiles by a controlled variation of impurity surface concentration C(o) in diffusion processes. High concentrations associated with conventional diffusion have various limitations. Such concentrations close to the surface are reduced by this method, while retaining a good profile or even an improved one at the diffusion front. It can also reduce the emitter dip phenomenon. The process uses a PBr(3) system with a nonoxidizing atmosphere. Since phospho-silicate glass is formed in only minute amounts, or not at all, during the diffusion operation, an increase or decrease in C(o) can result. Effects of varying C(o) on the profiles produced can be calculated and shown graphically. This technique controllably varies C(o) during a single cycle, that is, in a continuous process. U.S.

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Tailoring Impurity Profiles

This technique forms preselected impurity profiles by a controlled variation of impurity surface concentration C(o) in diffusion processes. High concentrations associated with conventional diffusion have various limitations. Such concentrations close to the surface are reduced by this method, while retaining a good profile or even an improved one at the diffusion front. It can also reduce the emitter dip phenomenon. The process uses a PBr(3) system with a nonoxidizing atmosphere. Since phospho-silicate glass is formed in only minute amounts, or not at all, during the diffusion operation, an increase or decrease in C(o) can result. Effects of varying C(o) on the profiles produced can be calculated and shown graphically. This technique controllably varies C(o) during a single cycle, that is, in a continuous process. U.S. Patent 2,868,678 mentions the possibility of changing C(o) to vary the diffusion profile for only successive cycles. The variation in impurity concentration is made from cycle to cycle, rather than as a continuous variation within a single cycle.

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