Pinned photodiode structure and method of formation
AssigneeAptina Imaging Corporation
InventorHoward E. Rhodes
Life of this patent
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Abstract
An imager having a photodiode with a shallow doping profile with respect to the top surface of a substrate is disclosed. An imager with a graded pinned surface layer, self-aligned to a gate stack is provided. A photodiode with a shallow doping profile with respect to the top surface of a substrate and a graded pinned surface layer, self-aligned to a gate stack is provided. These photodiodes exhibit reduced image lag, transfer gate leakage, and photodiode dark current generation.
Claims21
1-240. (canceled)
A method of forming a photoconversion device comprising:
- forming an oxide layer over a top surface of a substrate;
- forming a three-dimensionally graded doped region of a first conductivity type below the oxide layer and at the top surface of the substrate;
- and
- forming a charge collection region below the oxide layer and located at least in part beneath the three-dimensionally graded doped surface region, the charge collection region being doped to a second conductivity type.
A method of forming a photodiode structure comprising:
- forming a three-dimensionally graded doped region of a first conductivity type;
- and
- forming a charge collection doped region below the three-dimensionally graded doped region such that an undoped separation region is maintained at least partially between the three-dimensionally graded doped region and charge collection doped region.
A method for forming an image pixel structure comprising:
- forming a transistor gate stack on a substrate;
- and
- forming a photodiode comprising a pinned surface region and a charge collection region, wherein the pinned surface region comprises doped and undoped portions that are laterally offset from the transistor gate.
Dependencies are inferred from the claim text.