Image Sensor Pixel Array Crosstalk Reduction
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Solution Overview
Problem
CMOS image sensors face challenges in minimizing crosstalk between adjacent pixels due to reduced device isolation film width for higher resolution, leading to unsatisfactory light blocking characteristics and increased manufacturing costs from complex process steps.
Innovation Solution
The solution involves forming a pixel array with alternately arranged light receiving devices of different horizontal lengths, using device isolation films to create sufficient spaced distances between them, and incorporating buried light receiving devices to adjust amplification factors and compensate for photo sensitivity differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the unit pixel size is minimized to achieve higher resolution, then the image sensor resolution is improved, but the distance between photodiodes of adjacent unit pixels becomes closer, resulting in increased crosstalk occurrence frequency
Solution Approach 1:
The device isolation film is segmented into a first device isolation film and a second device isolation film formed in sequence. The first device isolation film provides basic isolation, while the second device isolation film adds enhanced light blocking capability. This segmentation allows the isolation structure to maintain effective crosstalk prevention even when the overall device isolation film width is reduced due to smaller pixel sizes.
Solution Approach 2:
The device isolation film employs a composite structure with two different isolation materials. The first device isolation film uses a first isolation material, and the second device isolation film uses a second isolation material with different optical properties. This composite approach optimizes both the electrical isolation and optical blocking functions, enabling effective crosstalk suppression in high-resolution sensors with reduced pixel dimensions.
2Measurement precision
If the device isolation film width is reduced to accommodate higher resolution, then the image sensor resolution is improved, but the light blocking characteristics become unsatisfactory
Solution Approach 1:
The device isolation film is segmented into a first device isolation film and a second device isolation film formed in sequence. The first device isolation film provides basic isolation, while the second device isolation film adds enhanced light blocking capability. This segmentation allows the isolation structure to maintain effective crosstalk prevention even when the overall device isolation film width is reduced due to smaller pixel sizes.
Solution Approach 2:
The device isolation film employs a composite structure with two different isolation materials. The first device isolation film uses a first isolation material, and the second device isolation film uses a second isolation material with different optical properties. This composite approach optimizes both the electrical isolation and optical blocking functions, enabling effective crosstalk suppression in high-resolution sensors with reduced pixel dimensions.
3Reliability
If the process of forming device isolation films by burying trenches is divided into forming the first device isolation film and forming the second device isolation film, then the light blocking characteristics are improved, but the manufacturing cost increases due to a relatively high number of processes
Solution Approach 1:
The formation of the first device isolation film and the second device isolation film is merged into a single continuous process step. Both isolation films are deposited in sequence without requiring separate trench formation and filling operations, thereby reducing the total number of manufacturing processes while maintaining the enhanced light blocking characteristics provided by the two-layer structure.
Solution Approach 2:
The first device isolation film is formed in advance before the second device isolation film. This preliminary action allows the first isolation layer to be established as a foundation, upon which the second isolation layer is subsequently added. This sequencing enables efficient process integration that reduces overall manufacturing complexity and cost while achieving superior light blocking performance.
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 effectively minimizes crosstalk by ensuring sufficient spaced distances between light receiving devices and adjusts signal values, resulting in improved light blocking and reduced manufacturing costs through simplified process steps.
Implementation Method 1
The second device isolation film 23 may be formed as an optical absorption film for absorbing incident light from the adjacent photodiodes 10 to minimize crosstalk generated between pixels
Data Source
AI summary
An image sensor may include a semiconductor substrate, a plurality of light receiving devices formed within the semiconductor substrate, and a plurality of device isolation films for isolating the light receiving devices from each other. When an arrangement direction of a pixel array may be formed by arranging the light receiving devices is a horizontal direction, the pixel array may be formed by alternately arranging a first type light receiving device and a second type light receiving device having different horizontal lengths.