Image Sensor Pixel Separation Structure for Dark Current Suppression
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Solution Overview
Problem
Current image sensors face challenges in reducing dark current and improving light sensitivity, which affect their performance in capturing high-quality images, especially in low-light conditions.
Innovation Solution
The design incorporates a semiconductor substrate with photoelectric conversion regions and a pixel separation structure that includes a conductive pattern, capping pattern, and gapfill pattern to enhance light sensitivity and reduce dark current, featuring a lattice structure that encloses pixel regions and uses a gapfill pattern to prevent substrate deformation and improve electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pixel separation structure is introduced to reduce dark current and prevent cross-talk, then dark current suppression and light sensitivity are improved, but device complexity and manufacturing difficulty increase due to the multi-layer structure including conductive pattern, capping pattern, and gapfill pattern
Solution Approach 1:
The pixel separation structure is divided into multiple functional layers: a conductive pattern for electrical connectivity, a capping pattern for protection and planarization, and a gapfill pattern for structural support. This segmentation allows each layer to perform its specific function optimally while collectively achieving dark current suppression and cross-talk prevention between adjacent pixel regions.
Solution Approach 2:
The conductive pattern is embedded within the gapfill pattern, which in turn is covered by the capping pattern. This nested configuration allows the conductive elements to be protected and integrated within the structural framework, reducing overall device complexity while maintaining the separation function.
2Reliability
If the pixel separation structure extends through the substrate to fully separate pixel regions, then cross-talk prevention is improved, but substrate deformation and manufacturing difficulty worsen
Solution Approach 1:
The pixel separation structure is strategically positioned at the boundaries between pixel regions rather than uniformly across the entire substrate. The gapfill pattern provides localized structural support where needed, while the conductive pattern is confined to specific separation regions. This localized approach prevents cross-talk at critical interfaces without causing substrate-wide deformation.
Solution Approach 2:
The pixel separation structure combines multiple materials with complementary properties: conductive material for electrical connectivity, capping material for mechanical protection and planarization, and gapfill material for structural support. This composite structure achieves effective pixel separation while distributing mechanical stresses to prevent substrate deformation.
3Productivity
If the conductive pattern is positioned to maximize electrical connectivity between photoelectric conversion regions, then charge transfer efficiency is improved, but dark current suppression worsens due to increased conductive pathways
Solution Approach 1:
The gapfill pattern serves as an intermediary between the conductive pattern and the photoelectric conversion regions. It provides structural support and controlled electrical isolation, allowing the conductive pattern to maintain efficient charge transfer pathways while preventing direct contact that would create unwanted leakage paths and dark current.
Solution Approach 2:
The conductive pattern is configured to establish equipotential regions that facilitate efficient charge collection and transfer. By maintaining uniform potential distribution across the photoelectric conversion regions, the conductive pattern maximizes charge transfer efficiency while the gapfill pattern prevents potential differences that would drive dark current through the conductive pathways.
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 suppresses dark current and maintains substrate integrity, leading to improved light sensitivity and image quality by preventing cross-talk between pixel regions and ensuring efficient charge transfer.
Implementation Method 1
a first photoelectric conversion region provided in the semiconductor substrate; a second photoelectric conversion region provided in the semiconductor substrate
Data Source
AI summary
An image includes a semiconductor substrate having a first surface and a second surface that face each other; a first photoelectric conversion region and a second photoelectric conversion region provided in the semiconductor substrate; a gapfill pattern that is interposed between the first and second photoelectric conversion regions and extends from the second surface toward the first surface, wherein a first side surface of the gapfill pattern faces the first photoelectric conversion region and a second side surface of the gapfill pattern faces the second photoelectric conversion region; and a conductive pattern disposed on the gapfill pattern. The conductive pattern includes a first portion disposed on the first side surface, a second portion disposed on the second side surface, and a connecting portion that is disposed on a top surface of the gapfill pattern and electrically connects the first portion to the second portion.