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Method of Measuring Diffusion Length In A Simple, Contactless Manner

IP.com Disclosure Number: IPCOM000048979D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Pak, MS: AUTHOR [+2]

Abstract

This article describes a method and apparatus for monitoring bulk defects in semiconductor material. The method and apparatus feature steps and means for measuring the diffusion lengths of carriers produced by sequentially illuminating a semiconductor substrate with light sources of different wavelengths.

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Method of Measuring Diffusion Length In A Simple, Contactless Manner

This article describes a method and apparatus for monitoring bulk defects in semiconductor material. The method and apparatus feature steps and means for measuring the diffusion lengths of carriers produced by sequentially illuminating a semiconductor substrate with light sources of different wavelengths.

The method includes the step of illuminating a semiconductor substrate with a first light source of a first wavelength, for example, a 0.65-micron red light. Following illumination with the first light source, the surface photovoltage resulting from photo-generated carriers is measured. The surface voltage may be measured, for example, with a capacitive probe disposed at the substrate surface.

After irradiation of the substrate with the first light source and the accompanying photovoltage measurement, the substrate is illuminated with a second light source of a wavelength different from the first light source, for example, a 0.94-micron infrared light. Thereafter, the associated substrate photovoltage is again measured, for example, with a capacitive probe at the substrate surface. Finally, ratios of the two photovoltage measurements are manipulated to determine carrier diffusion lengths and to infer semiconductor bulk defect density.

Apparatus for practicing the method is shown in the figure. The apparatus preferably includes a moveable vacuum chuck 2 for mounting a semiconductor substrate 1;...