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Stain For Locating PN Junctions

IP.com Disclosure Number: IPCOM000097555D
Original Publication Date: 1961-Feb-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Armstrong, WJ: AUTHOR

Abstract

An important step in the manufacture of a semiconductor device by diffusion techniques is the precise determination of the location of its PN junction. When the device is immersed in a suitable chemical solution, a staining action reveals an etch line which portrays the exact location of the junction. Optical means are then employed to measure the exact depth of diffusion.

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Stain For Locating PN Junctions

An important step in the manufacture of a semiconductor device by diffusion techniques is the precise determination of the location of its PN junction. When the device is immersed in a suitable chemical solution, a staining action reveals an etch line which portrays the exact location of the junction. Optical means are then employed to measure the exact depth of diffusion.

The following staining solution has proved to be particularly useful in locating PN junctions in silicon which has been doped with phosphorus, boron or gallium: 50-70 volumes of a 49% hydrofluoric acid solution

30-50 volumes of glacial acetic acid

1-30 drops of a 70% nitric acid solution

The acetic acid is effective to provide a buffering action which slows down the rate of attack of the solution on the silicon and renders the rate more controllable than is possible with prior staining solutions. This in turn assures a greater accuracy in portraying the PN junction by the shading of the stained regions.

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