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POCL(3) Liquid Diffusion Process Disclosure Number: IPCOM000092916D
Original Publication Date: 1967-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 31K

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This liquid POCL diffusion process employs an H(2)-N(2) carrier gas mixture.

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POCL(3) Liquid Diffusion Process

This liquid POCL diffusion process employs an H(2)-N(2) carrier gas mixture.

Silicon wafer 1 having diffusion mask 3 formed over one surface is positioned within diffusion chamber 5 and exposed to POCL(3) vapor transported in an H(2)-N(2) atmosphere. Wafer 1 is heated between 900 degrees C -1200 degrees C to effect P-type diffusion 7. Due to the absence of O(2) in chamber 5, a layer of phosphosilicate glass is not formed over the exposed surface of wafer
1. Also, at such lowtemperatures, HCL is not reactive with the exposed surface of wafer 1 so that pitting is avoided.

In prior techniques, the use of O(2)-N(2) carrier gas mixtures in liquid diffusion techniques resulted in the formation of a phosphosilicate layer over the exposed silicon surface, phosphorus diffusion being through such layer. The substitution of H(2) for O(2) in the carrier gas mixture avoids the formation of such layer and, also, prevents undesirable attack on the silicon surface by reactive gases, e. g., CL(2), released as by-products of the diffusion process.


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