Pixel Isolation Layout With Open Regions for Autofocus Image Sensors
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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 linearity of full wells and affect auto focusing and distance measurement capabilities.
Innovation Solution
Incorporating a second isolation layer with open regions between pixel regions, along with a passivation layer doped with P-type impurities, to improve light-receiving efficiency and linearity, while preventing light scattering and enhancing auto focusing and distance measurement functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolation layer is used to separate pixel regions, then pixel isolation is improved, but light-sensing sensitivity deteriorates
Solution Approach 1:
The isolation layer is designed with different properties in different regions: it has insulating properties where needed for pixel separation, but includes light-transmitting open regions where light sensing is required. This local differentiation allows the same structure to provide both isolation and light transmission functions.
Solution Approach 2:
The isolation layer is segmented into multiple regions including continuous isolation portions and open regions. This segmentation allows the isolation layer to provide electrical isolation between pixels while maintaining light transmission paths through the open regions to the photoelectric conversion devices.
2Reliability
If an isolation layer is used to separate pixel regions, then pixel isolation is improved, but linearity of full wells deteriorates
Solution Approach 1:
The isolation layer provides strong isolation in regions between pixels while maintaining open regions that allow uniform light distribution across the photoelectric conversion devices, thereby preserving the linearity of full wells through localized functional differentiation.
3Reliability
If an isolation layer is used to separate pixel regions, then pixel isolation is improved, but auto focusing capability deteriorates
Solution Approach 1:
The isolation layer is segmented to provide both isolation and light transmission functions, with open regions allowing light to reach photoelectric conversion devices for phase difference detection, thereby maintaining auto focusing capability while providing pixel isolation.
Solution Approach 2:
The open regions in the isolation layer act as intermediaries that allow light to pass through to the photoelectric conversion devices, enabling phase difference detection for auto focusing while the isolation layer itself maintains pixel separation.
4Reliability
If an isolation layer is used to separate pixel regions, then pixel isolation is improved, but distance measurement capability deteriorates
Solution Approach 1:
The isolation layer is segmented into isolation portions and open regions, where the open regions allow light transmission necessary for distance measurement while the isolation portions maintain pixel separation, thus preserving both functions simultaneously.
Solution Approach 2:
The isolation layer exhibits different optical properties in different locations: it is opaque in isolation regions for pixel separation but transparent in open regions to allow light transmission for distance measurement by the photoelectric conversion devices.
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 solution effectively enhances light-sensing sensitivity, improves linearity of full wells, and maintains the accuracy of auto focusing and distance measurement functions in image sensors.
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.