Optical Sensor Avalanche Multiplication Region Uniformity
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Solution Overview
Problem
In optical sensors with avalanche multiplication regions, non-uniform electric fields can lead to joint fracture and reduced light detection sensitivity due to the presence of hetero-conductive regions, causing variations in light receiving sensitivity among pixels.
Innovation Solution
The optical sensor incorporates a dual-layer avalanche multiplication region with varying impurity concentrations in different portions to extend the depletion layer uniformly, ensuring a consistent electric field and high sensitivity across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a hetero-conductive region is provided in the optical sensor, then charge collection efficiency is improved, but electric field uniformity deteriorates causing joint fracture
Solution Approach 1:
The patent applies local quality by creating different impurity concentration zones within the multiplication region. Specifically, a first multiplication region with higher impurity concentration is positioned adjacent to the hetero-conductive region, while a second multiplication region with lower impurity concentration is positioned away from it. This local differentiation allows the depletion layer to extend uniformly across both regions, maintaining electric field uniformity while preserving the charge collection benefits of the hetero-conductive region.
2Productivity
If impurity concentration is increased in the multiplication region, then avalanche multiplication efficiency is improved, but electric field uniformity deteriorates
Solution Approach 1:
The patent implements local quality by establishing distinct impurity concentration zones: the first multiplication region adjacent to the hetero-conductive region has higher impurity concentration to ensure adequate avalanche multiplication, while the second multiplication region has lower impurity concentration to maintain electric field uniformity. This spatial differentiation of impurity concentrations allows each region to optimize its function while contributing to overall system performance.
Solution Approach 2:
The multiplication region is segmented into two distinct zones with different impurity concentrations. The first multiplication region (higher impurity concentration) and second multiplication region (lower impurity concentration) are spatially separated and positioned at different locations relative to the hetero-conductive region. This segmentation enables independent optimization of avalanche multiplication efficiency and electric field uniformity in different parts of the device.
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 uniformizes the electric field in the avalanche multiplication region, preventing joint fracture and enhancing light receiving sensitivity uniformly across all pixels, thereby improving the overall performance of the optical sensor.
Implementation Method 1
a voltage is applied between a front surface and a back surface of a substrate to cause avalanche multiplication in an avalanche multiplication region. As a result, electrons generated in the substrate are multiplied
Implementation Method 2
a depletion layer is more likely to spread in a portion of the avalanche multiplication region overlapping the hetero-conductive region than in a portion thereof overlapping the charge collection region
Data Source
AI summary
An optical sensor includes an avalanche multiplication region including a first multiplication region having a first conductive type and a second multiplication region having a second conductive type, each of the first multiplication region and the second multiplication region being formed in a layer shape, a charge collection region having the second conductive type disposed on a first side of the second multiplication region, and a first conductive region having the first conductive type disposed on the first side of the second multiplication region. The second multiplication region has a first portion overlapping the charge collection region in a thickness direction of the first multiplication region and the second multiplication region and a second portion overlapping the first conductive region in the thickness direction. A concentration of impurities in the first portion is higher than a concentration of impurities in the second portion.