Imaging Pixel Charge Collection Protection Region Design
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Solution Overview
Problem
Imaging devices face inefficiencies due to photons not reaching photosensors and electrons being lost or mixed with dark current, leading to reduced quantum efficiency and image quality issues.
Innovation Solution
Incorporating a charge collecting protection region of a different conductivity type below the storage region but not below the photosensor, which collects excess electrons and prevents them from reaching the storage regions, thereby mitigating cross-talk, blooming, and dark current interference, while allowing photons to be effectively captured by photosensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge collecting protection region is provided below the storage region, then cross-talk and blooming are mitigated, but photons may be blocked from reaching photosensors
Solution Approach 1:
The protection region is segmented to be discontinuous below the photosensor, with gaps or openings that allow photons to reach the photosensor while still providing charge collection protection in other areas. This segmentation resolves the contradiction by spatially dividing the protection function from the photon transmission path.
Solution Approach 2:
The protection region is designed with non-uniform properties - it is continuous in areas where charge collection is needed (below storage regions) and discontinuous or absent in areas where photon transmission is critical (below photosensors). This local differentiation allows simultaneous achievement of cross-talk mitigation and high quantum efficiency.
2Reliability
If excess electrons are collected to prevent dark current interference, then image quality improves, but electron loss increases
Solution Approach 1:
The protection region extracts or removes excess electrons and dark current carriers from the substrate before they can interfere with pixel operation. By taking out these harmful charge carriers through the protection region, the patent improves image quality while the discontinuous design ensures signal electrons are not unnecessarily removed.
Solution Approach 2:
The protection region converts harmful dark current electrons and excess charge carriers into beneficial effects by collecting and removing them. The same structural feature that could potentially trap signal electrons is designed to preferentially collect dark current and excess charge, turning a potential harm into a benefit for image quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances quantum efficiency by preventing electron loss and interference, resulting in improved image quality and reduced uneven brightness in reconstructed images.
Implementation Method 1
The photosensors each absorb incident radiation of a particular wavelength (e.g., optical photons or x-rays) and produce a signal corresponding to the intensity of light impinging on that element
Implementation Method 2
A charge collecting protection region of a first conductivity type is provided in at least some pixel cells below the storage region but not below the photosensor in the same pixel cell. The charge collecting protection region is capable of collecting excess electrons present in the imaging device substrate
Data Source
AI summary
A method, apparatus, and system that provides one or more charge collecting protection regions in a pixel array, each formed below a storage region of a pixel cell, but not below at least one photosensor of one pixel of the array. The storage region includes a floating diffusion region and/or a storage gate in the pixel cell of the imaging device. The protection regions can keep stray charges from reaching the storage regions.