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Insert Gas Buffer for Reduction of Metallic Contamination during Capsule Diffusion

IP.com Disclosure Number: IPCOM000049361D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Brochon, S: AUTHOR [+4]

Abstract

During high temperature diffusion processing of semiconductor wafers in a closed capsule (e.g., as subcollector diffusion), there occurs undesired contamination of the wafers by metallic contaminants, such as copper, iron, nickel.

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Insert Gas Buffer for Reduction of Metallic Contamination during Capsule Diffusion

During high temperature diffusion processing of semiconductor wafers in a closed capsule (e.g., as subcollector diffusion), there occurs undesired contamination of the wafers by metallic contaminants, such as copper, iron, nickel.

A method to reduce this contamination by providing an inert gas flow acting as a buffer between the capsule and the tube is herein described.

In the conventional process a boat loaded with the wafers to be processed and the diffusant source are disposed in a capsule, which is then evacuated and sealed. The loaded capsule is inserted into a tube through the load/unload part. A pressure gradient exists between the tube and the capsule tending to facilitate any contaminants disseminated in the glassware to diffuse into the interior of the capsule, hence contaminating the wafers. Recently it has been recognized that this contamination was caused mainly by the heating elements of the furnace.

As a consequence, it was understood that this contamination may be avoided. if, unlike the standard process, the capsule is inserted into a quartz tube and a flow of inert gas, such as argon, is established inside the quartz tube to keep the Cu, Fe. Ni vapor pressure low enough by permanently evacuating any contaminants provided by the heating elements of the furnace. Experiments which have been conducted at 1200 degrees C have demonstrated a drastic reduction of copper,...