Phototransistor array having uniform current response and method

Details Phototransistor array having uniform current response and method Phototransistor array having uniform current response and method

1975-12-12

1978-03-07

Miller, Jr., Stanley D.

29572, 29574, H01L 2714

Patent

active

040782433

ABSTRACT:
Variations of current gain from element to element in a phototransistor array are eliminated by covering the array with an opaque mask and etching openings in the mask over each phototransistor based upon an area reduction factor (ARF). The area reduction factor for an opening is equal to (I.sub.m /I.sub.x).sup.1-n where n is a constant definitive of the change in beta of a phototransistor in the array over a given range of collector currents; I.sub.m is the minimum collector current measured for the array and I.sub.x is the collector current for the phototransistor beneath the opening. Based upon the ARF's, the openings etched in the mask or cover initiate uniform current from each phototransistor element when uniform light flux is directed on the array. The process of fabricating the array comprises measuring the collector current for each phototransistor element at a given uniform light flux; determining the element with minimum collector current in the array; calculating the ARF for each phototransistor to achieve a uniform current response from the array; coating the array with an opaque cover, and etching the cover at each phototransistor based upon the ARF.

REFERENCES:
patent: 3448344 (1969-06-01), Schuster et al.
patent: 3558974 (1971-01-01), Stewart
patent: 3584183 (1971-06-01), Chiaretta et al.
patent: 3774088 (1973-11-01), Magdo et al.
patent: 3858233 (1974-12-01), Miyata et al.
patent: 3925879 (1975-12-01), Weinstein
Eisenmann et al., "Polymer Field Stop for Electrooptic Device," IBM Technical Disclosure Bulletin, vol. 17, No. 3, Aug. 1974, pp. 935-936.

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