Semitest, Inc.

Raytheon Company

Sergey Liberman

Peter L Domenicali

Glendon P Marston

Alan H Field

Charles M Kohn

Brian T Cunningham

Donald L Lee

Martin Rommel

Tony T Tang

Richard F Adams

Semiconductor material characterizing method and apparatus

A method and apparatus are provided for determining the doping concentration profile of a specimen of semiconductor material. The specimen is positioned between a pair of electrodes, the specimen being disposed on one of the electrodes and being spaced form the other electrode by a nonconductive medium. In one implementation of the invention the nonconductive medium is air. A region of the surface of the specimen is illuminated with a beam of light of wavelengths shorter than that corresponding to the energy gap of the semiconductor material and which is intensity modulated at a predetermined frequency. A variable DC bias voltage is applied between the pair of electrodes, the variable DC bias voltage varying between that corresponding to accumulation and that corresponding to deep depletion for the specimen. The intensity of the light beam is low enough and the speed at which the DC bias voltage is varied is fast enough such that no inversion layer is formed at the surface of the specimen. A signal is also provided corresponding to the total capacitance between the two electrodes during the DC bias voltage sweep. A signal is provided representing the ac photocurrent induced at the region of the specimen illuminated by the light beam. The intensity of the light beam and frequency of modulation of the light beam are selected such that the ac photocurrent is nearly proportional to the intensity of the light beam. The doping concentration profile is then determined using the ac photocurrent, the total capacitance and the DC bias voltage. The apparatus includes a sensor assembly having a sensor tip which is mounted on an air bearing assembly. The air bearing assembly is suspended from a housing by a pair of bellows. In use, air is supplied to the air bearing assembly through the bellows causing the bellows to expand, lowering the sensor tip until the air bearing action stops the expansion. In another implementation of the invention, a light beam is not employed and the doping concentration profile is determined using the total capacitance, the capacitance of air, the DC bias voltage and the area of the electrode spaced from the specimen information.

Method and apparatus for characterizing a specimen of semiconductor

A method for determining the doping concentration profile of a specimen of semiconductor material. The specimen is positioned between a pair of electrodes, the specimen being disposed on one of the electrodes and being spaced from the other electrode by an air gap. A signal is provided corresponding to the total capacitance between the two electrodes. A region of the surface of the specimen is illuminated with a beam of light of wavelengths shorter than that corresponding to the energy gap of the semiconductor material and which is intensity modulated at a predetermined frequency. A variable DC bias voltage is applied between the pair of electrodes, the variable bias voltage varying between that corresponding to accumulation and that corresponding to deep depletion for the specimen. The intensity of the light beam is low enough and the speed at which the DC bias voltage is varied is fast enough such that no inversion layer is formed at the surface of the specimen. A signal is provided representing the ac photocurrent induced at the region of the specimen illuminated by the light beam. The intensity of the light beam and frequency of modulation of the light beam are selected such that the ac photocurrent is nearly proportional to the intensity of the light beam. The doping concentration profile is then determined using the ac photocurrent, the total capacitance and the DC bias voltage.

Method utilizing a modulated light beam for determining characteristics

An infrared energy detection apparatus having a first array of infrared detectors adapted to detect infrared energy of a first wavelength and produce an electrical signal corresponding to such detected energy, and a second array of infrared detectors, positioned to intercept infrared energy passing through the first array, and adapted to detect energy of a second wavelength in such intercepted energy and produce an electrical signal corresponding to such detected energy. The first array of infrared detectors includes an array of detector devices formed along a lower portion thereof adapted to detect a portion of radiation impinging on the upper portion thereof and, electronic circuitry disposed between the upper and lower portions and connected to the detector devices for producing electrical signals representative of the detected energy having the first wavelength. The second array of infrared detectors includes an array of detector devices adapted to detect a portion of radiation passed through the first array of detectors and impinging on the second array and having the second wavelength and, electronic circuitry for producing electrical signals representative of the detected energy having the second wavelength. The first array of infrared detectors has formed therein an array of lenses to direct infrared energy impinging on the upper surface to the detector devices formed in the first array.

Radiation detection apparatus

Growing community of inventors

Bedford, MA, United States of America

Sergey Liberman