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Optoelectronic Determination of Diffusion Pocket Depth and Minority Carrier Diffusion Lengths

IP.com Disclosure Number: IPCOM000082788D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 19K

Publishing Venue

IBM

Related People

Patrin, NA: AUTHOR

Abstract

A simple nondestructive measurement of diffused or implanted junction depth in semiconductor bodies can be realized, by exposing the junction to three different wavelengths of light and measuring the photocurrent generated by each wavelength.

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Optoelectronic Determination of Diffusion Pocket Depth and Minority Carrier Diffusion Lengths

A simple nondestructive measurement of diffused or implanted junction depth in semiconductor bodies can be realized, by exposing the junction to three different wavelengths of light and measuring the photocurrent generated by each wavelength.

When a diffusion pocket has its outer edges shielded by an opaque material, so that only the central portion of the pocket is exposed and monochromatic light having a wavelength Lambda is directed at the surface, a uniform photoflux Phi(0) impinges on the semiconductor surface.

As these photons travel through the semiconductor they are absorbed and hole-electron pairs created.

If the diffusion pocket is simultaneously reverse biased, then the field around the function separates the holes and the electrons leading to a detectable photocurrent.

The equation describing this photocurrent I is:.

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Thus in this equation LMD, LMS, and x are unknowns. But by measuring I at three different values of Lambda , the three equations can be solved for the three unknowns and the junction depth calculated.

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