Uniform-bridge-gradient time-of-flight photodiode for image sensor pixel
AssigneeShenzhen Goodix Technology Co., Ltd.
InventorRobert Daniel MCGRATH
Life of this patent
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Abstract
A uniform bridge gradient (UBG) time-of-flight (ToF) photodiode block is described, such as for integration with image sensor pixels. The UBG ToF photodiode block can be part of a UBG ToF pixel, and an image sensor can include an array of such pixels. Each UGB ToF photosensor block has multiple taps for selective activation, and a photodiode region designed for complete and rapid transit of photocarriers, as they are generated, via the multiple taps. Embodiments of the photodiode region include a photodiode-defining implant, a relatively shallow first bridging implant, and relatively deep second bridging implant. The bridging implants provide lateral bridging with a uniform doping gradient near and across the multiple taps.
Claims20
A uniform-bridge-gradient (UBG) time-of-flight (ToF) photodiode block comprising:
- a plurality of taps disposed onto a semiconductor substrate of a first doping type, the plurality of taps comprising at least a first readout tap and a second readout tap, each of the plurality of taps having one of a plurality of transfer gates configured for selective activation by an activation network;
- a photodiode region implanted into the semiconductor substrate and comprising:
- a photodiode-defining implant of a second doping type complementary to the first doping type implanted to a first implant depth over the photodiode region;
- a first bridging implant of the second doping type implanted to a second implant depth over a first portion of the photodiode region that forms a first lateral bridge region across the plurality of taps along an edge of the photodiode region nearest to the plurality of taps;
- and
- a second bridging implant of the second doping type implanted to a third implant depth over a second portion of the photodiode region that forms a second lateral bridge region across the plurality of taps and at least partially overlaps with both the photodiode-defining implant and the first bridging implant, the third implant depth being deeper than both the first implant depth and the second implant depth.
A complementary metal-oxide semiconductor (CMOS) image sensor (CIS) comprising:
- a semiconductor substrate of a first doping type;
- an array of uniform-bridge-gradient (UBG) time-of-flight (ToF) pixels integrated with the semiconductor substrate, each UBG ToF pixel having a respective one of a plurality of UBG ToF photodiode blocks, each UBG ToF photodiode block comprising:
- a plurality of taps disposed onto the semiconductor substrate and comprising at least a first readout tap and a second readout tap, each of the plurality of readout taps having a respective one of a plurality of transfer gates configured for selective activation by an activation network and a respective one of a plurality of collection nodes;
- a photodiode region implanted into the semiconductor substrate and comprising:
- a photodiode-defining implant of a second doping type complementary to the first doping type implanted to a first implant depth over the photodiode region;
- a first bridging implant of the second doping type implanted to a second implant depth over a first portion of the photodiode region that forms a first lateral bridge region across the plurality of taps along an edge of the photodiode region nearest to the plurality of taps;
- and
- a second bridging implant of the second doping type implanted to a third implant depth over a second portion of the photodiode region that forms a second lateral bridge region across the plurality of taps and at least partially overlaps with both the photodiode-defining implant and the first bridging implant, the third implant depth being deeper than both the first implant depth and the second implant depth.
Dependencies are inferred from the claim text.