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Measuring Diffusion Surface Concentration

IP.com Disclosure Number: IPCOM000089953D
Original Publication Date: 1968-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Gardner, EE: AUTHOR [+2]

Abstract

This measurement technique provides an indication of impurity ion surface concentration in a semiconductor. When two materials of different index of refraction are brought together and if the top media has an index of refraction which is greater than the lower media, there is an angle of incidence at which the incident light is totally reflected. In undergoing this reflection, the light penetrates the short distance into the second media before being reflected. The absorption coefficient in the infrared of silicon is a function of the number of impurity atoms. When the light enters the second media, it is attenuated by this absorption. Thus, the reflected light is a measure of the number of impurity atoms.

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Measuring Diffusion Surface Concentration

This measurement technique provides an indication of impurity ion surface concentration in a semiconductor. When two materials of different index of refraction are brought together and if the top media has an index of refraction which is greater than the lower media, there is an angle of incidence at which the incident light is totally reflected. In undergoing this reflection, the light penetrates the short distance into the second media before being reflected. The absorption coefficient in the infrared of silicon is a function of the number of impurity atoms. When the light enters the second media, it is attenuated by this absorption. Thus, the reflected light is a measure of the number of impurity atoms. The method consists of reflecting infrared light from the surface of a semiconductor through a media having an index of refraction which is greater than the silica at an angle at which the light is totally reflected. The amount of attenuation is measured and is compared with a standard which gives the correlation of attenuation and number of impurity ions. The method is particularly useful for determining high carrier concentrations because the absorption coefficient is high and the technique is therefore very sensitive.

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