Pixel Separation Structure for Autofocus Image Sensor Crosstalk
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Solution Overview
Problem
Current image sensors face challenges in achieving optimal optical and electrical characteristics, particularly in auto-focusing applications, due to issues with cross-talk between pixel regions and inefficient light management, which affect the accuracy and efficiency of auto-focusing operations.
Innovation Solution
The image sensor incorporates a pixel isolation structure and separation structures between photoelectric conversion regions, which are designed to prevent cross-talk and enhance light absorption by spacing the separation structures apart from the pixel isolation structure, allowing for improved signal differentiation and auto-focusing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If separation structures are placed close to pixel isolation structure, then cross-talk between pixel regions is reduced, but light absorption efficiency decreases
Solution Approach 1:
The separation structure is positioned at a different vertical level (depth) than the photoelectric conversion regions, specifically at the same level as the photoelectric conversion regions while the pixel isolation structure extends deeper. This dimensional arrangement allows the separation structure to block lateral cross-talk between adjacent pixels while minimizing its impact on vertical light absorption paths.
Solution Approach 2:
The pixel isolation structure and separation structure are configured with different spatial characteristics - the pixel isolation structure forms deep trenches that extend below the photoelectric conversion regions, while the separation structure is positioned at the level of the photoelectric conversion regions. This creates localized isolation zones with different geometries optimized for respective functions: deep isolation for cross-talk prevention and shallow separation for light path preservation.
2Object-affected harmful factors
If pixel isolation structure is designed with deep trenches, then cross-talk prevention is improved, but manufacturing complexity increases
Solution Approach 1:
The isolation function is divided into two separate structures with different depths and positions: the pixel isolation structure that extends deep below the photoelectric conversion regions for primary isolation, and the separation structure at the photoelectric conversion region level for secondary separation. This segmentation allows each structure to be optimized independently for its specific function rather than requiring a single complex deep trench structure.
3Loss of energy
If separation structure is positioned at the same level as photoelectric conversion regions, then light absorption is enhanced, but cross-talk blocking effectiveness may be reduced
Solution Approach 1:
The solution operates in three-dimensional space by positioning the separation structure at the same vertical level as the photoelectric conversion regions while the pixel isolation structure extends to greater depths. This creates a multi-level isolation system where the separation structure blocks cross-talk at the photoelectric conversion level without obstructing the vertical light absorption paths, and the deeper pixel isolation structure provides additional cross-talk prevention.
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 reduces cross-talk between pixel regions, increases light absorption, and enhances the accuracy of auto-focusing operations by improving the difference between signals from photoelectric conversion regions, leading to better image sensor performance.
Implementation Method 1
first and second photoelectric conversion regions disposed in the first pixel region
Data Source
AI summary
An image sensor may include a pixel isolation structure disposed in a semiconductor substrate to define a first pixel region, first and second photoelectric conversion regions disposed in the first pixel region, and a separation structure disposed in the first pixel region, between the first and second photoelectric conversion regions. The pixel isolation structure may include first pixel isolation portions, which are spaced apart from each other in a second direction and extend lengthwise in a first direction, and second pixel isolation portions, which are spaced apart from each other in the first direction and extend lengthwise in the second direction to connect to the first pixel isolation portions. The separation structure may be spaced apart from the pixel isolation structure in the first direction and the second direction, and is at least partly at the same level as the first and second photoelectric conversion regions in a third direction perpendicular to the first direction and the second direction.