Noninvasive method and apparatus for characterization of semiconductors
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United States of America Patent
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May 2, 1989
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N/A
app pub date -
Jan 20, 1988
filing date -
Jan 20, 1988
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Abstract
A method and apparatus are described for characterizing a semiconductor using the surface photovoltage (SPV) effect. A region of the surface of the semiconductor is illuminated with an intensity modulated beam of light, the wavelength of the light being shorter than that corresponding to the energy gap of the semiconductor. The surface photovoltage (SPV) induced in the semiconductor is measured under bias voltage conditions. The intensity of the light beam and the frequency of modulation are selected such that the surface photovoltage (SPV) is directly proportional to the intensity and reciprocally proportional to the frequency of modulation. Using the surface photovoltage (SPV) and the bias voltage (V.sub.g) measurements, the charge induced in the semiconductor space charge region (Q.sub.sc) and the charge induced in the semiconductor (Q.sub.ind) are determined. This information is used to determine various parameters of the semiconductor including surface state density and oxide/insulator charge. The technique is designed especially for use in characterizing semiconductor wafers, coated or uncoated, but may, if desired, also be used in characterizing MIS or MOS type semiconductor devices.
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