Photoelectric Conversion Pixel Shielding for Stable Black Level
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Solution Overview
Problem
Existing photoelectric conversion apparatuses face challenges in stabilizing the black level detected by light-shielded pixels while maintaining sensitivity in the light-receiving region, as insufficient light shielding can lead to variations in black level and decreased sensitivity due to the thickness of the light-shielding structure.
Innovation Solution
The apparatus is designed with a light-shielding film and wall structure where the thickness of the light-shielding film in the light-shielded pixel region is greater than that of the light-shielding wall, and the light-shielding film has a higher light absorption coefficient than the wall, ensuring effective light shielding without compromising sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the light-shielding structure is increased to improve black level stability, then light shielding performance is improved, but sensitivity of light-receiving pixels decreases due to light beam blocking
Solution Approach 1:
The patent applies different light-shielding structures with different optical properties to different regions: the light-shielding film in the light-shielded pixel region has higher light absorption and greater thickness, while the light-shielding wall in the light-receiving pixel region has lower light absorption and controlled thickness to prevent sensitivity loss. This local differentiation resolves the contradiction by optimizing each region for its specific function.
Solution Approach 2:
The patent changes the optical parameters (light absorption coefficient) and geometric parameters (thickness) of the light-shielding structures based on regional requirements. The light-shielding film has higher light absorption and greater thickness compared to the light-shielding wall, allowing effective light blocking in the OB region while maintaining light transmission in the light-receiving region.
2Reliability
If a light-shielding structure is formed in the light-receiving pixel region to improve light shielding, then black level detection is improved, but light beams are blocked resulting in decreased sensitivity
Solution Approach 1:
The patent implements a differentiated light-shielding strategy where the light-shielding wall in the light-receiving pixel region has optimized thickness and lower light absorption compared to the light-shielding film in the OB region. This allows the light-shielding wall to provide necessary light blocking for black level detection while maintaining sufficient light transmission for pixel sensitivity.
Solution Approach 2:
The patent divides the light-shielding function into two separate structures: a light-shielding film in the light-shielded pixel region and a light-shielding wall in the light-receiving pixel region. Each structure is independently optimized for its specific regional requirements, allowing the light-shielding wall to provide minimal necessary shielding without compromising overall sensitivity.
3Reliability
If the thickness of the light-shielding film is made greater than the light-shielding wall, then light shielding performance in OB region is improved, but manufacturing complexity increases
Solution Approach 1:
The patent specifies that the light-shielding film has a greater thickness than the light-shielding wall, optimizing light shielding performance in the OB region. While this creates a parameter differentiation requirement, the use of standard semiconductor fabrication processes for forming films of different thicknesses makes the manufacturing complexity manageable within existing industrial capabilities.
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 stabilizes the black level detection in the light-shielded pixel region while preventing a decrease in sensitivity in the light-receiving region by optimizing the light-shielding performance.
Implementation Method 1
the light-shielding film has a higher light absorption coefficient than the wall
Implementation Method 2
a plurality of photoelectric conversion elements 11 arranged in an image pickup plane
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
Photoelectric conversion apparatus includes semiconductor layer in which first photoelectric converters are arranged in light-receiving region and second photoelectric converters are arranged in light-shielded region, light-shielding wall arranged above the semiconductor layer and defining apertures respectively corresponding to the first photoelectric converters, and light-shielding film arranged above the semiconductor layer. The light-shielding film includes first portion extending along principal surface of the semiconductor layer to cover the second photoelectric converters. The first portion has lower surface and upper surface. The light-shielding wall includes second portion whose distance from the semiconductor layer is larger than distance between the upper surface and the principal surface. Thickness of the first portion in direction perpendicular to the principal surface is larger than thickness of the second portion in direction parallel to the principal surface.