Abstract: A method and apparatus are provided for determining the doping concentration profile of a specimen of semiconductor material. 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 other implementations of the invention, photocurrent or photovoltage are not used 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.

Abstract: 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.

Abstract: 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.

Abstract: A method is provided for determining the minority carrier surface recombination lifetime constant (t.sub.s) 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. A signal is provided corresponding to the capacitance between the specimen and the electrode spaced from the specimen. A region of the surface of the specimen is illuminated with a beam of light of predetermined wavelengths and which is intensity modulated at a predetermined frequency and varying in intensity over a predetermined range. A fixed bias voltage V.sub.g applied between the pair of electrodes, the fixed bias voltage being of a value such that the semiconductor surface is in a state of depletion or inversion,. A signal is provided representing the ac photocurrent induced at the region of the specimen illuminated by the light beam.

Abstract: An apparatus for making ac surface photovoltage (SPV) measurements of a specimen of semiconductor material under dc bias voltage conditions includes a light source whose output beam is intensity modulated, an adjustable dc bias voltage source, a conductive base for supporting the specimen and a novel capacitance type reference electrode assembly for sensing the SPV signals. The reference electrode assembly includes in one embodiment a button made of insulating elastomeric material and attached to a rigid plate made of insulating material. A film made of insulating material and having a conductive coating on one side which serves as a reference electrode is attached to the button. When SPV measurements are being taken, the film is pressed against the specimen with pressure sufficient to hold the reference electrode in close compliance with the specimen, with pressure being applied to the plate from an external source and being transmitted from the rigid plate to the film through the elastomeric button.

Abstract: An apparatus for making ac surface photovoltage (SPV) measurements of a specimen of semiconductor material under variable dc bias voltage conditions includes a light source whose output beam is intensity modulated, a reference electrode, a guard electrode, a back electrode, a first voltage for biasing the reference electrode with a variable dc voltage and a second voltage separate from the first voltage for biasing the guard electrode such that an accumulation layer is established in the area on the specimen controlled by the guard electrode to prevent flow of carriers between the area controlled by the reference electrode and the rest of the specimen.

Abstract: An apparatus for making ac surface photovoltage (SPV) measurements of a specimen of semiconductor material under dc bias voltage conditions includes a light source whose output beam is intensity modulated, an adjustable dc bias voltage source, a conductive base for supporting the specimen and a novel capacitance type reference electrode assembly for sensing the SPV signals. The reference electrode assembly includes in one embodiment a transparent flexible sheet of insulating material having on one surface a first conductive coating which serves as a reference electrode and a second conductive coating which serves as a guard electrode, the first coating being transparent. The flexible sheet of insulating material is attached to a flat glass plate through an annular spacer. An elastomeric button is positioned between the sheet and the glass plate.

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.