Fabrication of low leakage-current backside illuminated photodiodes
First Claim
1. A method of fabricating a low-leakage current photodiode array comprising:
- defining frontside structures for a photodiode on a front side of a substrate;
forming a heavily-doped gettering layer on a back surface of the substrate;
carrying out a gettering process on the substrate to transport undesired components from the substrate to said gettering layer, and to form another layer in addition to said gettering layer, which is a heavily-doped, conductive, crystalline layer within the substrate;
after said gettering process, removing the entire gettering layer; and
after said removing, thinning the heavily-doped, conductive, crystalline layer within the substrate to create a native optically transparent, conductive bias electrode layer.
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Abstract
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.
127 Citations
10 Claims
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1. A method of fabricating a low-leakage current photodiode array comprising:
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defining frontside structures for a photodiode on a front side of a substrate;
forming a heavily-doped gettering layer on a back surface of the substrate;
carrying out a gettering process on the substrate to transport undesired components from the substrate to said gettering layer, and to form another layer in addition to said gettering layer, which is a heavily-doped, conductive, crystalline layer within the substrate;
after said gettering process, removing the entire gettering layer; and
after said removing, thinning the heavily-doped, conductive, crystalline layer within the substrate to create a native optically transparent, conductive bias electrode layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification