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Self Gettering Capsule Diffusion Furnace

IP.com Disclosure Number: IPCOM000052694D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Beaufrere, P: AUTHOR [+2]

Abstract

During diffusion processing of semiconductor wafers in a capsule, to minimize or eliminate metallic contamination traceable to the capsule material, the seal-off mechanism or the furnace used to heat the capsule, the capsule is placed into a tube or furnace which can be pumped down to a pressure lower than that inside the capsule. In such an arrangement, contaminant diffusion is favored in a direction away from the interior of the capsule.

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Self Gettering Capsule Diffusion Furnace

During diffusion processing of semiconductor wafers in a capsule, to minimize or eliminate metallic contamination traceable to the capsule material, the seal-off mechanism or the furnace used to heat the capsule, the capsule is placed into a tube or furnace which can be pumped down to a pressure lower than that inside the capsule. In such an arrangement, contaminant diffusion is favored in a direction away from the interior of the capsule.

At high temperatures under the influence of a pressure gradient, diffusion of contaminants proceeds in the direction of the pressure gradient according to the equation See Original Page 853 where N = concentration, Delta P = pressure gradient, A and d are capsule dimensions, and K is the permeation coefficient appropriate to the diffusing species, the medium through which it is diffusing and the temperature.

Generally, in capsule diffusions, there is a strong pressure gradient tending to assist any contaminants in quartz tubes or quartz capsules to diffuse into the interior of the capsule, hence contaminating the wafer load.

As indicated in the figure, a boat loaded with appropriate wafers which are to be diffused and the diffusant source are placed in the capsule, which is then evacuated and sealed. The loaded capsule is inserted into the tube through the load/unloading port, and the tube is sealed. The tube is then pumped down to a pressure lower than that inside the capsule, which wil...