Image Sensor Grid Trench Layout to Reduce Boundary Stain Defects
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Solution Overview
Problem
Image sensors face challenges in reducing stain defects due to the step between the active pixel sensor region and the optical black sensor region, which affects light reception efficiency and sensitivity.
Innovation Solution
A grid trench is formed between the active pixel sensor region and the optical black sensor region, with at least part of the grid pattern and conductive pattern located inside the trench, reducing the step and potential defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a grid pattern is formed between the active pixel sensor region and the optical black sensor region, then light reception efficiency is improved, but a step is created between the two regions causing stain defects
Solution Approach 1:
The grid pattern is nested inside the grid trench, which is formed as a recessed structure between the active pixel sensor region and the optical black sensor region. This nesting approach allows the grid pattern to be positioned within the trench depth, reducing the step height between regions while maintaining the light reception function of the grid pattern.
Solution Approach 2:
The grid trench introduces a vertical dimension (depth) to the structure, transitioning from a planar grid pattern to a three-dimensional configuration. By extending the grid pattern into the vertical space within the trench, the solution reduces the lateral step between regions while preserving the optical functionality.
2Illumination intensity
If the grid pattern is formed on the surface, then light reception efficiency is improved, but stain defects occur due to the step between regions
Solution Approach 1:
The grid pattern is nested within the grid trench structure, positioning it partially or fully inside the recessed region. This reduces the exposed step height at the surface, minimizing the harmful stain defects while maintaining sufficient light reception capability through the trench opening.
Solution Approach 2:
The grid trench acts as an intermediary structure between the grid pattern and the surface, mediating the transition and reducing the direct step exposure. The trench walls and depth provide a gradual transition that minimizes stain defects while allowing the grid pattern to function.
3Manufacturing precision
If a grid trench is formed to reduce the step, then stain defects are reduced, but device complexity increases
Solution Approach 1:
The grid trench divides the boundary region into distinct segments (trench depth, trench width, surface level), allowing independent optimization of each segment. This segmentation enables the step reduction function while maintaining a systematic, manufacturable structure despite the increased complexity.
Data Source
AI summary
An image sensor is provided. An image sensor includes: a substrate including an active pixel sensor region, an optical black sensor region, and a boundary region provided between the active pixel sensor region and the optical black sensor region; a photoelectric conversion element provided inside the substrate on the boundary region; a passivation layer provided on the substrate; a grid trench formed on the boundary region of the substrate and extending from an upper surface of the passivation layer toward an inside of the passivation layer; grid patterns, each of the grid patterns being provided on the passivation layer on each of the active pixel sensor region and the boundary region of the substrate, at least a part of a grid pattern being provided inside the grid trench; and a color filter provided between the grid patterns.