Image Sensor Pixel Isolation With Open Regions for Light Sensitivity
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Solution Overview
Problem
Existing image sensors face challenges in maintaining light-sensing sensitivity due to isolation layers, which can reduce the effectiveness of auto focusing and distance measurement functions.
Innovation Solution
An image sensor design incorporating a second isolation layer with an open region between pixel regions, along with a passivation layer doped with P-type impurities, to improve light-receiving efficiency and linearity of full wells, thereby enhancing auto focusing and distance measurement capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation layers are used to separate pixel regions, then pixel isolation and signal separation are improved, but light-sensing sensitivity is reduced
Solution Approach 1:
The second isolation layer is selectively formed only in regions between adjacent pixel regions where isolation is needed, while leaving open regions that do not interfere with light sensing. This local differentiation allows the structure to provide isolation where required while maintaining light-sensing sensitivity in critical areas.
Solution Approach 2:
The isolation structure is divided into multiple layers: a first isolation layer surrounding each pixel region and a second isolation layer between pixel regions. This segmentation allows different portions of the isolation structure to serve different functions - the first layer provides comprehensive pixel isolation while the second layer provides inter-pixel region isolation without compromising light sensing.
2Reliability
If isolation layers are added to improve pixel separation, then pixel crosstalk is reduced, but device complexity increases
Solution Approach 1:
The second isolation layer serves multiple functions simultaneously: it isolates adjacent pixel regions from each other, defines the boundaries of open regions, and works in conjunction with the first isolation layer to provide comprehensive pixel separation. This multi-functionality reduces the need for additional separate structures.
3Reliability
If the isolation layer completely surrounds pixel regions, then pixel isolation is maximized, but light-receiving efficiency is reduced
Solution Approach 1:
The second isolation layer is selectively positioned only in areas where isolation between pixel regions is needed, while leaving open regions that allow light to reach the photoelectric conversion devices. This local differentiation optimizes both isolation performance and light-receiving efficiency.
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
The design prevents light-sensing sensitivity reduction, improves linearity of full wells, and enhances the accuracy of auto focusing and distance measurement functions by optimizing the structure of the image sensor.
Implementation Method 1
a passivation layer doped with P-type impurities
Implementation Method 2
Each of the first pixel region and the second pixel region include a photoelectric conversion device
Data Source
AI summary
An image sensor is provided. The image sensor includes a first pixel region and a second pixel region located within a semiconductor substrate, a first isolation layer surrounding the first pixel region and the second pixel region, a second isolation layer located between the first pixel region and the second pixel region, and a microlens arranged on the first pixel region and the second pixel region. Each of the first pixel region and the second pixel region include a photoelectric conversion device. The second isolation layer includes at least one first open region that exposes a portion of an area located between the first pixel region and the second pixel region.