Digirad Corporation

Diglrad Corporation

Lars S Carlson

Shulai Zhao

John F Sheridan

Alan Mollet

Joel Kindem

Richard Wilson

An indirect connection to and across a photodiode array. The backside contact is used as one portion which connects to a capacitor. The capacitor forms a shunt across the bulk substrate, thus shunting across the series resistance of the substrate, and reducing the series resistance.

Capacitive bypass

Ultra-low leakage current backside-illuminated semiconductor photodiode arrays are fabricated using a method of formation of a transparent, conducting bias electrode layer that avoids high-temperature processing of the substrate after the wafer has been gettered. As a consequence, the component of the reverse-bias leakage current associated with strain, crystallographic defects or impurities introduced during elevated temperature processing subsequent to gettering can be kept extremely low. An optically transparent, conductive bias electrode layer, serving as both an optical window and an ohmic backside equipotential contact surface for the photodiodes, is fabricated by etching through the polysilicon gettering layer and a portion of the thickness of heavily-doped crystalline silicon layer formed within, and near the back of, the substrate during the gettering process.

Fabrication of low leakage-current backside illuminated photodiodes

A passive mechanism suppresses injection, into any active guard regions interposed between the edge of a photodiode array chip and the outer photodiode pixels or into the outer pixels themselves, of minority carrier current generated in the physically disrupted region at the edge of the semiconductor die created by cleaving, sawing or otherwise separating the chip from the remainder of the wafer on which the die was fabricated. A thin metallic layer covers all or part of the edge region, thereby creating a Schottky barrier. This barrier generates a depletion region in the adjacent semiconductor material. The depletion region inherently creates an energy band distribution which preferentially accelerates minority carriers generated or near the metal-semiconductor interface towards the metal, thereby suppressing collection of these carriers by any active regions of the guard structure or by the photodiode pixels.

Technique for suppression of edge current in semiconductor devices

An embedded power supply for providing a voltage on a detector module within an imaging system provides the required potential to the module from charge stored on an output capacitor. Charge on the capacitor is replenished by injecting, commonly referred to as pumping, current into the capacitor by pulses of current generated by switching mode circuitry. Charge pumping into the capacitor is efficient because energy is stored in low-loss passive components and transferred into the low-loss output capacitor through low-impedance paths. Switching noise of the power supply is eliminated by turning off the charge pumping circuit during periods when such noise would disrupt the operation of the module, for example when the module is reading out image data. The output capacitor is large enough to supply the required voltage to the module for a certain period when the capacitor is not being pumped.

Charge pump power supply with noise control

A semiconductor interconnection device having a semiconductor die, a plurality of epoxy bonds, and an array of insulating islands is disclosed. The semiconductor die has a plurality of conductive contacts. The plurality of epoxy bonds has a metallic substance such as silver. The epoxy bonds are configured to provide interconnection between the semiconductor die and an external structure. The plurality of epoxy bonds is selectively applied to the plurality of conductive contacts on the semiconductor die and corresponding conductive contacts on the external structure. The array of insulating islands is coupled to the plurality of conductive contacts. The islands are configured to prevent migration of the metallic substance from the plurality of epoxy bonds to the semiconductor die through the plurality of conductive contacts.

Insulator/metal bonding island for active-area silver epoxy bonding

A semiconductor imaging device is disclosed. The device includes a substrate having at least first and second surfaces opposing each other, and a circuit layer. The substrate is doped to exhibit a first conductivity type. The substrate includes a conducting layer, a region, and a plurality of doped regions. The conducting layer includes a first type dopants incorporated near the first surface. The region includes a heavily doped area within the substrate near the second surface. The plurality of doped regions includes a second type dopants formed on the second surface. The circuit layer is formed over the second surface to provide gate contacts to and readout circuits for the plurality of doped regions. The readout circuit provides readout of optical signals from pixels.

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Del Mar, CA, United States of America

Lars S Carlson