Pixel Separating Pattern Layout for Low-Dark-Current Image Sensors
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Solution Overview
Problem
Image sensors face challenges in reducing dark current and enhancing sensitivity, particularly due to the limitations of existing pixel separating patterns which can deteriorate sensitivity and increase dark current generation.
Innovation Solution
The proposed image sensor incorporates a pixel separating pattern with a conductive second separating pattern and non-conductive first and third separating patterns, where the second separating pattern is closer to the substrate's first side, and the edges of the third separating pattern overlap the second separating pattern, allowing for effective voltage application to reduce dark current and maintain sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional pixel separating pattern is used, then pixel separation is achieved, but dark current increases and sensitivity deteriorates
Solution Approach 1:
The pixel separating pattern is divided into three distinct segments: a first separating pattern (non-conductive), a second separating pattern (conductive), and a third separating pattern (non-conductive). Each segment serves a specific function: the first segment provides initial isolation, the second segment actively suppresses dark current through voltage application, and the third segment provides final isolation. This segmentation allows the pattern to simultaneously achieve pixel separation, dark current reduction, and sensitivity preservation.
Solution Approach 2:
Different portions of the pixel separating pattern are assigned different electrical properties (conductive vs. non-conductive) based on their specific functional requirements. The conductive second separating pattern is positioned where active dark current suppression is needed, while the non-conductive first and third separating patterns are positioned where electrical isolation is prioritized. This local differentiation of properties enables the system to reduce dark current without compromising overall sensitivity.
2Object-affected harmful factors
If a conductive separating pattern is used to reduce dark current, then dark current is suppressed, but sensitivity may be compromised
Solution Approach 1:
The separating pattern is segmented into conductive and non-conductive portions, allowing dark current suppression in specific regions while maintaining sensitivity in others. The conductive second separating pattern is confined to specific locations where dark current generation is most problematic, while non-conductive patterns are positioned where sensitivity preservation is critical.
Solution Approach 2:
The pixel separating pattern exhibits spatially varying electrical properties: conductive regions are placed where dark current suppression is most beneficial, while non-conductive regions are placed where maintaining signal integrity and sensitivity is paramount. This local quality differentiation resolves the contradiction by allowing both dark current reduction and sensitivity maintenance in different locations within the same structure.
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 configuration effectively reduces dark current and enhances sensitivity by allowing for precise voltage application to the conductive region, preventing dark current generation while maintaining the image sensor's sensitivity.
Implementation Method 1
the second separating pattern is conductive... allowing for effective voltage application to reduce dark current
Implementation Method 2
The photodiode converts incident light into electric signals
Data Source
AI summary
An image sensor includes: a substrate including a first side and a second side facing the first side; pixels including a photoelectric conversion layer in the substrate and a transistor on the first side of the substrate; and a pixel separating pattern between the pixels, wherein the pixel separating pattern includes a first separating pattern, a second separating pattern, and a third separating pattern, the second separating pattern is conductive, and the first separating pattern and the third separating pattern are non-conductive, the second separating pattern is nearer the first side of the substrate than is the third separating pattern, and a first end of the first separating pattern, a first end of the second separating pattern, and a first end of the third separating pattern are on the second side of the substrate.