Browse Prior Art Database

Plug Type Vacuum Diffusion System

IP.com Disclosure Number: IPCOM000077282D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Benjamin, CE: AUTHOR

Abstract

Vacuum diffusion is a widely employed technique for forming impurity-doped surface layers in semiconductor devices, the usual vehicle for diffusing impurities being a sealed evacuated quartz capsule or ampoule in which the wafers and impurity source are placed, the capsule being evacuated, baked at an intermediate temperature, sealed off and then run through a diffusion time/temperature cycle in a diffusion furnace.

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Plug Type Vacuum Diffusion System

Vacuum diffusion is a widely employed technique for forming impurity-doped surface layers in semiconductor devices, the usual vehicle for diffusing impurities being a sealed evacuated quartz capsule or ampoule in which the wafers and impurity source are placed, the capsule being evacuated, baked at an intermediate temperature, sealed off and then run through a diffusion time/temperature cycle in a diffusion furnace.

The drawing illustrates an alternative arrangement wherein the wafers and source see the same time-temperature-ambient cycle as in the sealed capsules, but the tooling is significantly different. In the drawing, the wafers 10 and source 11, for example a powder, are loaded in a tray 13 which is fused to a tapered plug 14 made of quartz. A quartz diffusion tube 15 is provided having an enlarged diametrical portion 15A in which the wafers, loaded in the tray, may be prebaked, (typical temperatures 400-500 degrees C.) and a diffusion zone 15B in which the temperature may be raised to approximately 900 degrees - 1250 degrees C. to effect diffusion. The junction between the portion 15A and 15B includes a tapered frustoconical socket portion 15C in which the plug 14 may be tightly fitted.

The plug 14 is connected by a bayonet joint 16 to a quartz push rod 17, which passes through a wafer load and unload, pump down and cooling zone 18, and then through a quartz sleeve push rod guide 19 into a plug and push-rod wall
20. The p...