CMOS Image Sensor Isolation Layout for Overflow Charge Crosstalk
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Solution Overview
Problem
CMOS image sensors experience crosstalk between adjacent pixels due to overflown photocharges, leading to increased noise, which is exacerbated as pixel size decreases.
Innovation Solution
Incorporating a first isolation region to absorb overflown photocharges and a second isolation region made of insulation material to physically prevent the movement of these charges between adjacent photoelectric conversion elements, thereby reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pixel size is decreased to increase pixel density, then pixel density is improved, but crosstalk between adjacent pixels increases due to overflown photocharges
Solution Approach 1:
The patent introduces isolation regions that segment the continuous semiconductor substrate into electrically independent pixel regions. These isolation regions act as barriers that divide the pixel array, preventing photocharge migration between adjacent pixels while maintaining high pixel density through effective use of available space.
Solution Approach 2:
The isolation regions serve as intermediary structures between adjacent photoelectric conversion elements. By introducing this intermediate layer with different electrical properties, the patent blocks the harmful interaction (photocharge migration) between pixels while allowing each pixel to function independently.
2Object-affected harmful factors
If isolation regions are added to reduce crosstalk, then noise is reduced, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the isolation regions: they provide electrical isolation between pixels, absorb excess photocharges, and maintain physical separation. This consolidation of functions into a single structural element reduces overall device complexity compared to implementing separate mechanisms for each function.
Solution Approach 2:
The isolation regions are designed to perform multiple functions simultaneously: blocking photocharge migration, absorbing overflow charges, and providing structural separation. This multi-functionality reduces the need for additional specialized components, thereby managing device complexity.
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 effectively reduces noise in CMOS image sensors by electrically and physically isolating adjacent pixels, improving image quality and reducing the impact of miniaturization on full well capacity.
Implementation Method 1
configured to receive a voltage to generate an electric field to attract photocharges from the first photoelectric conversion element or the second photoelectric conversion element
Implementation Method 2
configured to physically prevent movement of the overflown photocharges
Implementation Method 3
each of the first photoelectric conversion element and the second photoelectric conversion element configured to generate photocharges in response to incident light
Data Source
AI summary
An image sensing device is provided to include a first photoelectric conversion element and a second photoelectric conversion element that are arranged adjacent to each other; a first isolation region located between the first and second photoelectric conversion elements and configured to receive a voltage to generate an electric field to attract photocharges from the first or second photoelectric conversion element; and a second isolation region separated from the first isolation region, the second isolation region located between the first and second photoelectric conversion elements and structured to include an insulation material to block photocharges from moving between the first and second photoelectric conversion elements.