Semitest, Inc.

Karl Suss America, Inc.

Peter L Domenicali

Alan H Field

Glendon P Marston

Sergey Liberman

Charles M Kohn

Martin Rommel

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

A proximity mask alignment system includes a remotely-focusing microscope and a video frame storage device. When a first surface, such as an integrated circuit substrate, is in focus an image of the first surface is obtained and stored. Then, after the microscope is re-focused to a second surface, such as a photomask, the stored image of the first surface is superimposed onto the 'live' image of the second surface. The two focal positions are stored, with a selected one being normally provided to the microscope. A user initiates an automatic sequence wherein the microscope focuses to the other focal position, stores an image obtained at the other focal position, then refocuses to the original focal position. The stored image is superimposed on the image currently being generated, enabling the user to simultaneous view each surface in sharp focus, facilitating the alignment of the two surfaces to one another.

Proximity mask alignment using a stored video image

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Montpelier, VT, United States of America

Peter L Domenicali