Photodiode Depth Isolation Layout for Autofocus Sensitivity
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Solution Overview
Problem
Existing photoelectric conversion devices, such as those using avalanche diodes and photodiodes, do not adequately consider the relationship between the position in the thickness direction of the semiconductor substrate and the function of photodiodes, leading to suboptimal performance in autofocusing and light detection, particularly for subjects with stripe patterns or parallax issues.
Innovation Solution
A photoelectric conversion device is designed with a specific structure where photodiodes are arranged in a semiconductor substrate with isolation regions at different depths, allowing for optimized signal charge generation and isolation, enhancing sensitivity and reducing noise, and incorporating a unique layout for improved autofocusing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If photodiodes are arranged in a single layer at the same depth in the substrate, then the structure is simple and easy to manufacture, but the sensitivity and layout flexibility are insufficient
Solution Approach 1:
The patent transitions from a single-layer photodiode arrangement to a multi-layer structure where photodiodes are positioned at different depths (first depth and second depth) within the substrate. This dimensional change in the depth direction enables improved sensitivity and layout flexibility while maintaining manufacturing feasibility through systematic isolation region design
2Object-affected harmful factors
If isolation regions are arranged to separate photodiodes completely, then the noise reduction is effective, but the layout flexibility and sensitivity are reduced
Solution Approach 1:
The isolation region is divided into multiple segments positioned at different depths: a first isolation region at the first depth and a second isolation region at the second depth. This segmentation allows selective isolation of specific photodiode regions while maintaining connectivity and sensitivity in other areas, achieving a balance between noise reduction and layout flexibility
Solution Approach 2:
Different regions of the isolation structure have different properties: the first isolation region isolates second regions of photodiodes at the first depth, while the second isolation region isolates first regions of photodiodes at the second depth. This local differentiation of isolation functionality allows optimized noise reduction in specific areas while preserving overall layout flexibility and sensitivity
3Reliability
If photodiodes are positioned deeper in the substrate, then the sensitivity to incident light is improved, but the signal charge movement and avalanche multiplication are affected
Solution Approach 1:
The patent utilizes the depth dimension to position photodiodes at multiple levels (first depth and second depth) rather than relying solely on horizontal positioning. This allows optimization of light absorption sensitivity at deeper positions while maintaining controlled signal charge movement pathways through the multi-layer isolation structure
Solution Approach 2:
The multi-layer isolation regions act as intermediaries that selectively block and guide signal charge movement. The first and second isolation regions work together to control charge flow from the light-sensitive regions at different depths to the readout circuits, ensuring proper signal extraction while maintaining the sensitivity benefits of deep-substrate positioning
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 optimized structure improves the sensitivity and accuracy of autofocusing, particularly for subjects with stripe patterns, by tailoring the photodiode arrangement and isolation regions to specific depths within the substrate, leading to enhanced image quality and reduced noise.
Implementation Method 1
a first region that generates signal charges by photoelectrically converting an incident light
Implementation Method 2
An avalanche diode that can detect a weak light at a single photon level by using avalanche (electronic avalanche) multiplication
Data Source
AI summary
Provided is a photoelectric conversion device including: a first substrate having a first face; photodiodes arranged in the first substrate and each having a first region that generates signal charges by photoelectrically converting an incident light and a second region that receives the signal charges moving from the first region; a first isolation region arranged in the first substrate at a first depth and including a first portion extending in a first direction so as to isolate the second regions from each other; and a second isolation region arranged in the first substrate at a second depth deeper than the first depth from the first face, and including a second portion extending in a second direction intersecting the first direction in plan view so as to isolate the first regions from each other, and the first and second portions are partially overlapped with each other in plan view.