Pixel Isolation Layout for Dense Image Sensors With Lower Light Loss
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Solution Overview
Problem
Current image sensors face challenges in improving integration density and performance, particularly in reducing light loss and enhancing autofocus capability due to the design of isolation structures and microlens overlap.
Innovation Solution
The image sensor incorporates an isolation structure with extension portions that have a width reduction region, allowing for spaced microlens overlap and an inclined side surface, which reduces light loss and improves autofocus by preventing microlens isolation structure overlap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation structures are provided between pixel regions to reduce interference, then light loss and interference between pixels are reduced, but integration density decreases due to the additional space occupied by isolation structures
Solution Approach 1:
The isolation structure is divided into a main isolation portion surrounding the pixel region and multiple extension portions that extend between adjacent pixels. This segmentation allows the isolation function to be distributed throughout the pixel array, providing effective signal isolation while minimizing the total space occupied compared to a continuous isolation structure.
Solution Approach 2:
The extension portions are positioned specifically at locations where light interference and crosstalk between adjacent pixels occur most frequently. By concentrating isolation resources locally at these critical interfaces rather than uniformly across the entire pixel region, the structure achieves effective interference reduction with minimal impact on integration density.
2Loss of energy
If extension portions of isolation structure are spaced apart to minimize light loss, then light collection efficiency is improved, but isolation effectiveness may be reduced
Solution Approach 1:
The isolation structure is divided into a main isolation portion surrounding the pixel region and multiple extension portions that extend between adjacent pixels. This segmentation allows the isolation function to be distributed throughout the pixel array, providing effective signal isolation while minimizing the total space occupied compared to a continuous isolation structure.
Solution Approach 2:
The extension portions act as intermediary isolation elements positioned between adjacent pixels. These extension portions provide gradual optical isolation at the interfaces where crosstalk occurs most, allowing light to be collected efficiently from each pixel while still providing effective isolation through the distributed extension portions that mediate between neighboring pixel regions.
Data Source
AI summary
An image sensor includes a substrate having first and second surfaces opposing each other; a circuit interconnection structure provided below the first surface of the substrate; a group provided in the substrate and including a plurality of pixel substrate regions; and an isolation structure provided in the substrate, wherein the isolation structure includes an isolation portion surrounding the group and extension portions extending from the isolation portion to a region between the plurality of pixel substrate regions of the group, wherein, in the group, the extension portions have end portions spaced apart from each other, and wherein at least one of the extension portions includes a width reduction region in which a width decreases in a direction away from the isolation portion.