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Browse Prior Art Database

Making a Polycrystalline Source for Capsule Boron Diffusion

IP.com Disclosure Number: IPCOM000095161D
Original Publication Date: 1965-Sep-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Benjamin, CE: AUTHOR

Abstract

This method diffuses boron impurity atoms into a wafer of semiconductor material such as silicon.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 100% of the total text.

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Making a Polycrystalline Source for Capsule Boron Diffusion

This method diffuses boron impurity atoms into a wafer of semiconductor material such as silicon.

A boron-silicon molten alloy is formed by heating elemental boron and silicon together in a quartz crucible to over 1400 degrees C. After approximately 15 minutes, the quartz crucible is allowed to cool in order to solidify the melt. There is formed a polycrystalline alloy with the crucible intimately attached. The segregation coefficient of boron in silicon is approximately 1. Thus, solidification of a boron-silicon melt results in the portion freezing first having approximately the same composition as the last portion to freeze. For any other impurity, such as phosphorous, antimony, etc., the last portion to freeze is far more heavily doped, resulting in a highly inhomogeneous alloy.

The crucible is dissolved away by soaking in HF for an appropriate time. The polycrystalline alloy, after rinsing, is ready to be crushed into diffusion source powder. This polycrystalline type source provides substantially the same diffusion result for both high and low concentrations as provided by a monocrystalline type source. Additionally, use of a polycrystalline type source reduces the preparation time required for making monocrystalline type sources.

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