Multi-Component Pixel Isolation Layout for Image Sensor Uniformity
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Solution Overview
Problem
Modern image sensors face challenges in maintaining electrical and optical isolation between pixel regions, leading to increased photo response non-uniformity and dark image non-uniformity due to reduced device features and asymmetric layouts, which degrade overall performance.
Innovation Solution
The implementation of an image sensor design featuring a shared pixel layout with a floating diffusion node at the crossroad of photodetectors, surrounded by well regions and an isolation structure comprising elongated and short isolation components with different heights, which increases electrical and optical isolation and symmetry, thereby enhancing device density and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device features are scaled down to increase device density, then device density is improved, but electrical and optical isolation between pixel regions deteriorates
Solution Approach 1:
The isolation structure is divided into multiple discrete isolation components positioned between adjacent pixel regions. Each isolation component acts as an independent barrier, collectively providing comprehensive electrical and optical isolation while allowing flexible arrangement to maintain high device density.
Solution Approach 2:
The isolation components extend in the vertical dimension (depth) into the substrate, creating isolation barriers that are not limited to the planar dimension. This vertical extension enables effective isolation even when horizontal spacing between pixel regions is reduced due to scaling.
2Reliability
If isolation structure is enhanced to improve electrical and optical isolation, then isolation performance is improved, but manufacturing complexity increases
Solution Approach 1:
Different isolation components are positioned at specific locations between pixel regions based on local isolation requirements. The isolation structure is optimized locally rather than uniformly across the entire sensor, reducing overall complexity while maintaining effective isolation where most needed.
Solution Approach 2:
The isolation components serve as intermediary elements between adjacent pixel regions, providing the necessary electrical and optical isolation without requiring complex modifications to the pixel regions themselves. This mediator approach simplifies the overall device architecture.
3Productivity
If isolation components are positioned closer to increase device density, then device density is improved, but photo response non-uniformity increases
Solution Approach 1:
The isolation structure is segmented into multiple discrete components rather than continuous barriers. This segmentation allows precise positioning of each component to maintain adequate distance from photodetector sensitive regions while still providing effective isolation, thus preserving photo response uniformity.
Solution Approach 2:
Isolation components extend vertically into the substrate, providing isolation functionality in the depth dimension. This allows horizontal spacing between pixel regions to be reduced for higher density while the vertical isolation barriers prevent optical crosstalk that would cause photo response non-uniformity.
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 effectively increases electrical and optical isolation, reduces photo response and dark image non-uniformity, and mitigates damage during manufacturing processes, resulting in improved image sensor performance and device stability.
Implementation Method 1
Each of the pixel regions comprise a photodetector disposed within the substrate and configured to convert incident radiation to charge carriers
Data Source
AI summary
Various embodiments of the present disclosure are directed towards an image sensor including a plurality of photodetectors disposed within a substrate. The photodetectors are disposed respectively within a plurality of pixel regions. A floating diffusion node is disposed along a front-side surface of the substrate at a middle region of the plurality of pixel regions. A plurality of well regions is disposed within the substrate at corners of the plurality of pixel regions. An isolation structure extends into a back-side surface of the substrate. The isolation structure comprises a plurality of elongated isolation components disposed between adjacent pixel regions, a middle isolation component aligned with the floating diffusion node, and multiple peripheral isolation components aligned with the plurality of well regions. The elongated isolation components have a first height and the middle and peripheral isolation components have a second height less than the first height.