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Source for Capsule Diffusion Process

IP.com Disclosure Number: IPCOM000089958D
Original Publication Date: 1968-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Joshi, ML: AUTHOR [+2]

Abstract

In capsule diffusion, the maximum obtainable surface concentration of an impurity corresponds to the impurity concentration of the source powder when the exposed surface of the latter is optimized. The obtaining of a uniform, high impurity concentration across a wafer has always been beset with difficulties, for example, in the isolation diffusion of boron. The peripheries of silicon wafers are often eroded or microalloyed in such conventional processing, and the regions so altered are unusable. In the standard process, the source powder is in a single quartz boat or dish in the bottom of the capsule, directly beneath the wafers. By distributing a number of receptacles around the interior periphery of the capsule, either the persistent erosion or microalloying or both effects,produced by conventional processing, are minimized.

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Source for Capsule Diffusion Process

In capsule diffusion, the maximum obtainable surface concentration of an impurity corresponds to the impurity concentration of the source powder when the exposed surface of the latter is optimized. The obtaining of a uniform, high impurity concentration across a wafer has always been beset with difficulties, for example, in the isolation diffusion of boron. The peripheries of silicon wafers are often eroded or microalloyed in such conventional processing, and the regions so altered are unusable. In the standard process, the source powder is in a single quartz boat or dish in the bottom of the capsule, directly beneath the wafers. By distributing a number of receptacles around the interior periphery of the capsule, either the persistent erosion or microalloying or both effects,produced by conventional processing, are minimized. In this capsule jig, four quartz source- powder boats are spaced around the wafers within the quartz capsule at approximately 90 degrees intervals around the periphery. Wafers processed by this method have a distribution of sheet resistance comparable with that of conventionally processed wafers. Sheet conductivity from wafer to wafer is much more uniform than in the standard wafers. The technique was very useful, for example, in the preparation of 8 x 8 memory devices with 2-1/4 inch diameter wafers.

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