Image Sensor Floating Diffusion and Well Pickup Biasing
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Solution Overview
Problem
Current image sensing devices face challenges in achieving improved dynamic range and low-illuminance characteristics, which are crucial for high-performance applications in various fields such as automotive and medical industries.
Innovation Solution
The design of an image sensing device incorporating a semiconductor substrate with photoelectric conversion elements, a floating diffusion region, and complementary conductivity source/drain and well pickup regions, along with a pixel array structure that includes shared transistors and a bias voltage system to enhance photocharge conversion and bias voltage application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional image sensing device structures are used, then manufacturing is simpler, but dynamic range and low-illuminance characteristics are insufficient
Solution Approach 1:
The pixel region is divided into multiple photoelectric conversion elements (first, second, third, and fourth photoelectric conversion elements) with different photoelectric conversion characteristics. This segmentation allows each element to optimize for specific lighting conditions, improving overall dynamic range and low-illuminance performance without requiring complete structural redesign of the entire device.
Solution Approach 2:
Different regions of the pixel array are assigned different photoelectric conversion characteristics through localized doping concentration variations and microlens positioning. This local quality approach enables specific areas to excel at capturing low-illuminance signals while other areas maintain high dynamic range capabilities, resolving the contradiction between performance and complexity.
2Reliability
If more photoelectric conversion elements are added to improve dynamic range, then device complexity increases
Solution Approach 1:
Multiple photoelectric conversion elements with different characteristics are merged within a single pixel region, sharing common structures such as the floating diffusion region and microlens array. This merging approach increases dynamic range capabilities while minimizing the increase in overall device complexity by reusing shared components.
Solution Approach 2:
The floating diffusion region and associated circuitry serve multiple functions by receiving signals from different photoelectric conversion elements with varying characteristics. This multi-functionality allows the same structural components to handle diverse photoelectric conversion outputs, improving dynamic range without proportionally increasing 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
This configuration improves dynamic range and low-illuminance characteristics by optimizing photocharge handling and bias voltage management, leading to enhanced operational performance in image sensing applications.
Implementation Method 1
at least one photoelectric conversion element formed in a semiconductor substrate including a first surface and a second surface opposite to the first surface, and configured to generate photocharges by performing photoelectric conversion of incident light received through the first surface
Data Source
AI summary
An image sensing device includes a substrate structured to include a first surface on a first side of the substrate and a second surface on a second side of the substrate opposite to the first side and to further include a first active region and a second active region in a portion of the substrate near the second surface, at least one photoelectric conversion element formed in the substrate, and structured to generate photocharges by performing photoelectric conversion of incident light received through the first surface of the substrate, a floating diffusion region formed near the second surface of the substrate, and structured to receive the photocharges from the photoelectric conversion element and temporarily store the received photocharges, a transistor formed in the first active region, and structured to include a first source/drain region coupled to the floating diffusion region, and a well pickup region formed in the second active region, and structured to apply a bias voltage to the substrate. The first source/drain region and the well pickup region have complementary conductivities and are formed to be in contact with each other.