Photosensitive diode array storage target

Claim 2

A photosensitive target with storage properties for converting an optical image to an electronic image, comprising: a semiconductor substrate of a first conductivity type, upon said substrate, an array of zones of a second conductivity type forming, with said substrate an array of photodiodes, means for reverse biasing said photo-diodes, said photodiodes being constituted by "hyper-abrupt" junctions whose junction capacitance C varies in accordance with the reverse bias voltage V applied to them by said reverse biasing means, in proportion with V - m , where m>1/2, and upon said array of photo-diodes an array of insulating material zones, said insulating material zones being disposed between said photo-diodes.

Claim 3

A photosensitive target according to claim 1, wherein each of said hyper-abrupt junctions is constituted successively, working from the substrate towards the surface where are disposed said insulating material zones, by a first zone containing impurities of the same kind as those in the substrate, and by a second zone comprising impurities of opposite kind to those in the substrate, the impurity concentration of said first zone being less than that of said second zone.

Claim 4

A photosensitive target according to claim 2, wherein said first zone of said junctions, constitute a continuous layer covering the substrate.

Claim 5

A method of manufacturing a photosensitive target according to claim 2, wherein: a semiconductor wafer or substrate is covered with a thin film of an insulating material; said thin film is etched in order to expose the surface of those zones of the substrate which are intended to constitute the array of photodiodes; a first, low-concentration diffusion operation, employing impurities of the same type as those encountered in the substrate, is carried out in order to create said first zones; a second, high-concentration diffusion operation, to a smaller depth than that reached by the first, using impurities of the opposite type to those encountered in the substrate, is carried out in order to create said second zones.

Claim 6

A method of manufacturing a photosensitive target according to claim 3, wherein: a semiconductor wafer or substrate is subjected to a first, low-concentration diffusion operation, using impurities of the same type as those encountered in said substrate, in order to form the continuous layer creating said first zones; the wafer thus processes, is covered with a thin film of insulating material; said thin film is etched in order to expose the surface of the processed wafer and those zones which are intented to constitute the network of photo diodes; a second, high concentration diffusion operation, to a smaller depth than that reached by the first operation, using impurities of the type opposite to those encountered in the substrate, is carried out in order to create said second zones.

Claim 7

A photosensitive target with storage properties for converting an optical image to an electronic image, comprising: an array of photo-diodes formed in a semiconductor substrate of a first conductivity type having a first kind of impurity, means for reverse biasing said photo-diodes, and an array of insulating material zones disposed between said photo-diodes, said photo-diodes being constituted (successively, working from the substrate towards the surface where are disposed said insulating material zones, by said substrate, by a first zone containing impurities of the same kind as those in said substrate, and by a second zone containing impurities of opposite kind to those in the substrate, the impurity concentration of said first zone being less than that of said second zone and more than that of said substrate, said photo-diodes thus being constituted by hyper-abrupt junctions.

Claim 8

A photosensitive target with storage properties for converting an optical image to an electronic image, comprising: an array of photo-diodes formed in a semiconductor substrate of a first conductivity type having a first kind of impurity, means for reverse biasing said photo-diodes, and an array of insulating material zones disposed between said photo-diodes, said photo-diodes being constituted (successively, working from the substrate towards the surface where are disposed said insulating material zones, by said substrate, by a first zone containing impurities of the same kind as those in said substrate, and by a second zone containing impurities of opposite kind to those in the substrate, the impurity concentration of said first zone being less than that of said second zone and more than that of said substrate, said photo-diodes thus being constituted by hyper-abrupt junctions.

Claim 9

A target according to claim 6 wherein said substrate and said first zone are N-type; and said second zone is P type, and said second zone has no direct contact with said substrate.

Claim 10

In a photosensitive target with storage properties for converting an optical image to an electronic image when scanned by an electron beam, said target comprising: an array of photo-diodes formed into a surface of a N-type semiconductor substrate having a predetermined impurity concentration; means for reverse biasing said photodiodes; and an array of insulating material zones disposed onto said surface of said substrate between said photo-diodes; the improvement consisting in realising each of said photo-diodes by a hyperabrupt junction, each said photo-diode being constituted successfully working from the side of said substrate opposite said surface supporting said insulating material zones, to said surface supporting said insulating material zone by: (a) said N-type substrate having said predetermined impurity concentration, (b) a zone of the N-type having an impurity concentration higher than that of said substrate, and (c) a zone of the P-type having an impurity concentration higher than that of said N-type zone, said N-type zones being interposed between said P-type zones and said substrate in such a way that said P-type zones have no contact with said N-type substrate.

Claim 11

In a photosensitive target with storage properties for converting an optical image to an electronic image when scanned by an electron beam, said target comprising: an array of photo-diodes formed into a surface of a N-type semiconductor substrate having a predetermined impurity concentration; means for reverse biasing said photodiodes; and an array of insulating material zones disposed onto said surface of said substrate between said photo-diodes; the improvement consisting in realising each of said photo-diodes by a hyperabrupt junction, each said photo-diode being constituted successfully working from the side of said substrate opposite said surface supporting said insulating material zones, to said surface supporting said insulating material zone by: (a) said N-type substrate having said predetermined impurity concentration, (b) a zone of the N-type having an impurity concentration higher than that of said substrate, and (c) a zone of the P-type having an impurity concentration higher than that of said N-type zone, said N-type zones being interposed between said P-type zones and said substrate in such a way that said P-type zones have no contact with said N-type substrate.