Method of making a light activated semiconductor controlled rect

Details Method of making a light activated semiconductor controlled rect Method of making a light activated semiconductor controlled rect

1975-03-25

1976-11-16

Tupman, W.

Metal working

Method of mechanical manufacture

Assembling or joining

29580, 29590, 357 30, B01J 1700

Patent

active

039914607

ABSTRACT:
A method is provided for making a light activated semiconductor controlled rectifier in a semiconductor body having opposed first and second major surfaces. Impurities are sequentially provided in the major surfaces to form four regions of alternate type conductivity disposed alternatively through the body between the major surfaces, with a PN junction between each region. An etchant solution is prepared preferably substantially equal amounts of chromium trioxide and water, and adding to said first solution just prior to use a given, preferably about 50% hydrofluoric acid solution in predetermined amounts preferably of substantially one part for each two parts of the first solution. All surfaces, except the first major surface of the diffused semiconductor body is masked with a material resistant to hydrofluoric acid, and the masked semiconductor body is immersed in the etchant solution to form light radiation reflecting pits, preferably in a tetrahedral pattern, in at least portions of the first major surface. A first electrode having an opening therethrough corresponding to a desired light radiation reflective means is formed on the first major surface, preferably before the immersion of the masked semiconductor body in the etchant solution, so that the etched pits are formed in the first major surface only where the light radiation reflective means is desired. The controlled rectifier is completed by forming on the second major surface a second electrode having an opening therethrough adapted to permit light radiation of preselected wavelength to penetrate the body and reflect from the light radiation reflective means.

REFERENCES:
patent: 2593447 (1952-04-01), Hesch
patent: 3088888 (1963-05-01), Leff
patent: 3107188 (1963-10-01), Hancock
patent: 3389457 (1968-06-01), Goldman
patent: 3466510 (1969-09-01), Mauta

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