Depth-Stratified Photodiode Isolation for Autofocus Accuracy
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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.
Innovation Solution
A photoelectric conversion device with a substrate structure that includes isolation regions at different depths, allowing for optimized arrangement of photodiodes to enhance signal charge generation and avalanche multiplication, improving sensitivity and reducing noise by varying the shape and area of isolation regions based on their depth and function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photodiodes are arranged in a single substrate without depth-based optimization, then device structure is simple, but sensitivity and autofocusing accuracy are insufficient
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement of photodiodes to a three-dimensional depth-stratified structure. Multiple isolation regions are positioned at different depths (first depth, second depth, third depth) within the substrate, creating vertical layering that enables differentiated functional zones. This depth-based dimensionality improvement allows simultaneous optimization of light detection and autofocusing functions without excessive planar complexity.
Solution Approach 2:
The substrate is segmented into multiple functional regions at different depths: first isolation regions for light detection, second isolation regions for autofocusing, and third isolation regions for additional functionality. Each segment serves a specific purpose, with photodiodes arranged in first regions, second regions, and third regions corresponding to different depth levels. This segmentation resolves the contradiction by distributing complexity vertically rather than horizontally.
2Reliability
If isolation regions are uniform in shape and area, then manufacturing is simple, but signal charge generation and avalanche multiplication are suboptimal
Solution Approach 1:
Different isolation regions are designed with locally optimized qualities: first isolation regions have specific shapes and areas optimized for light detection, while second isolation regions have different shapes and areas optimized for autofocusing. The third isolation regions further vary in configuration. This local quality differentiation improves signal charge generation and avalanche multiplication efficiency without requiring complex variable manufacturing processes, as each region type can be fabricated using standardized techniques tailored to its specific function.
3Measurement precision
If photodiodes are arranged without depth-based functional differentiation, then device structure is simple, but sensitivity for weak light detection is insufficient
Solution Approach 1:
The patent utilizes the depth dimension within the substrate to arrange photodiodes and isolation regions at different vertical levels. First photodiodes are positioned in first regions at a first depth, second photodiodes in second regions at a second depth, and third photodiodes in third regions at a third depth. This vertical stratification creates depth-based functional differentiation that enhances weak light detection sensitivity through optimized avalanche multiplication zones, while maintaining a relatively simple overall device structure without requiring multiple separate substrates or complex lateral arrangements.
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 approach enhances the sensitivity and accuracy of autofocusing and light detection by optimizing the structure of photodiodes within the substrate, improving image quality and focus detection across various subject patterns.
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.