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Increasing the Boron in Silicon Diffusion Level

IP.com Disclosure Number: IPCOM000076073D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Demsky, HM: AUTHOR [+2]

Abstract

In the method of diffusing boron in silicon using boron tribromide and water the low-doping levels of boron for base diffusions are believed to cause certain inversion problems and adequate ohmic contact to the low-doped silicon is difficult.

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Increasing the Boron in Silicon Diffusion Level

In the method of diffusing boron in silicon using boron tribromide and water the low-doping levels of boron for base diffusions are believed to cause certain inversion problems and adequate ohmic contact to the low-doped silicon is difficult.

Described is a method whereby a highly doped surface tends to eliminate the aforesaid problems and maintain the shape of the low-level boron profile. The process comprises utilizing a boron tribromide water system for diffusing boron into a silicon substrate, wherein a heavily doped glass phase is formed during the early stages of the diffusion process. This tends to diffuse the boron into the silicon substrate to a concentration near the solid solubility limit of boron in silicon, thereby forming a slightly or nondoped oxide layer at the silicon glass interface, which causes the diffusion of boron into the silicon to proceed in a gaussian manner and yield a typical profile. The highly doped silicon surface is accomplished by terminating the flow of oxidizing gases and allowing the silicon wafers to remain in an inert ambient, thereby allowing the boron from the heavily doped glass phase to diffuse through the glass barrier layer and further diffuse the boron into the silicon surface to a desired higher concentration.

The exact shape of the profile can be adjusted by the diffusion times in relation to the flow of diffusion gases.

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