Pixel Isolation Structure With Open Region for AF Contrast
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current image sensors face challenges in improving auto focusing (AF) contrast characteristics and dark current characteristics, particularly in the design of device isolation structures within the pixel array, which affect the overall performance and reliability of the image sensor.
Innovation Solution
The image sensor incorporates a device isolation structure with an open region between the first and second photoelectric conversion devices, allowing for improved movement of photocharges and application of a negative voltage to enhance AF contrast and reduce dark current, while also using microlenses and a semiconductor substrate with a device isolation structure that is continuous and physically connected for efficient charge management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a device isolation structure is used to separate pixels and photoelectric conversion devices, then dark current is reduced and photocharge movement is limited, but AF contrast characteristics deteriorate due to restricted photocharge movement between devices
Solution Approach 1:
The device isolation structure is designed with different properties in different regions: it has an open region (lower isolation) between the first and second photoelectric conversion devices to allow photocharge movement for AF contrast, and closed regions (higher isolation) between adjacent pixels to prevent dark current and photocharge leakage. This local differentiation resolves the contradiction by providing selective isolation levels where needed.
2Manufacturing precision
If the device isolation structure is continuous across the pixel array, then manufacturing precision is improved and photocharge containment is enhanced, but flexibility in optimizing individual pixel performance is reduced
Solution Approach 1:
The continuous device isolation structure is segmented into multiple regions with different configurations: open regions between photoelectric conversion devices within pixels, and closed regions between adjacent pixels. This segmentation allows the structure to simultaneously provide overall photocharge containment while enabling localized performance optimization for AF functionality.
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 solution enhances AF contrast characteristics and improves the reliability of the image sensor by limiting photocharge movement and reducing dark current, leading to better image capture performance.
Implementation Method 1
the device isolation structure opening a part between the first photoelectric conversion device and the second photoelectric conversion device, including an open region
Implementation Method 2
application of a negative voltage to enhance AF contrast and reduce dark current
Implementation Method 3
microlenses on the first photoelectric conversion device and the second photoelectric conversion device
Implementation Method 4
a first photoelectric conversion device and a second photoelectric conversion device inside the semiconductor substrate and included in each of the plurality of pixels
Data Source
AI summary
Provided is an image sensor including a device isolation structure. The image sensor includes a semiconductor substrate including a pixel array including a plurality of pixels, a first photoelectric conversion device and a second photoelectric conversion device inside the semiconductor substrate and included in each of the plurality of pixels, microlenses on the first photoelectric conversion device and the second photoelectric conversion device and a device isolation structure between the plurality of pixels and between the first photoelectric conversion device and the second photoelectric conversion device, the device isolation structure opening a part between the first photoelectric conversion device and the second photoelectric conversion device, including an open region at each edge of the plurality of pixels, and may be continuous in the pixel array.