Image Sensor Charge Storage Node Segmentation for Lag Reduction
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Solution Overview
Problem
Current image sensors face challenges in achieving improved optical characteristics, particularly in reducing image lag and blooming phenomena due to limitations in charge storage and photoelectric conversion efficiency.
Innovation Solution
The design incorporates a semiconductor substrate with a floating diffusion region, a barrier dopant region, and a charge drain region, along with an organic photoelectric conversion element and a buffer insulating layer, to effectively manage photocharges and reduce image lag by controlling the potential barrier and electric field within the charge storage node.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional charge storage node structure is used, then the device complexity is low, but image lag and blooming phenomena occur due to insufficient charge storage control
Solution Approach 1:
The charge storage node is segmented into multiple doped regions (first doped region, second doped region, third doped region) with different conductivity types. This segmentation allows independent control of charge storage and drainage functions, improving optical characteristics by reducing image lag and blooming while maintaining manageable device complexity through functional division.
Solution Approach 2:
Different regions within the charge storage node are assigned different local properties through doping variations. The first doped region has a first conductivity type, the second doped region has a second conductivity type, and the third doped region has a third conductivity type. This local quality differentiation enables precise control of charge behavior in specific areas, addressing optical characteristic issues without requiring complete structural redesign.
2Reliability
If the charge storage node directly contacts the photoelectric conversion element, then charge transfer efficiency is high, but blooming phenomenon occurs due to uncontrolled charge overflow
Solution Approach 1:
The charge storage node introduces intermediary doped regions (first, second, and third doped regions with alternating conductivity types) between the photoelectric conversion element and the charge drainage path. These intermediary regions act as controlled interfaces that enable efficient charge transfer while preventing uncontrolled charge overflow, thereby reducing blooming phenomenon without excessive structural complexity.
Solution Approach 2:
The invention changes the electrical parameters of the charge storage node by introducing multiple doped regions with different conductivity types and doping concentrations. This parameter variation enables dynamic control of charge storage capacity and charge transfer characteristics, improving charge storage control and reducing blooming while maintaining a relatively simple overall device configuration.
3Ease of manufacture
If a simple floating diffusion region is used, then the manufacturing process is simple, but image lag occurs due to insufficient charge drainage control
Solution Approach 1:
The floating diffusion region is segmented into multiple doped regions (first, second, and third doped regions) that can be formed using standard sequential doping processes. This segmentation provides precise charge drainage control to reduce image lag while maintaining ease of manufacture through compatibility with conventional semiconductor fabrication techniques.
Solution Approach 2:
The invention modifies the doping parameters of the charge storage node by introducing regions with different conductivity types and doping concentrations. These parameter changes enable improved charge drainage control to reduce image lag while maintaining ease of manufacture through standard doping process adjustments rather than requiring entirely new fabrication methods.
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 enhances the performance of image sensors by reducing image lag and blooming, resulting in clearer images and improved optical characteristics.
Implementation Method 1
a photoelectric conversion element configured to generate photocharges
Implementation Method 2
a barrier dopant region on the floating diffusion region in the semiconductor substrate
Data Source
AI summary
An image sensor includes a photoelectric conversion element and a charge storage node coupled to the photoelectric conversion element. The charge storage node may store photocharges generated in the photoelectric conversion element. The charge storage node may include a floating diffusion region in a semiconductor substrate, a barrier dopant region on the floating diffusion region in the semiconductor substrate, and a charge drain region on the barrier dopant region in the semiconductor substrate, where the semiconductor substrate is associated with a first conductivity type, the floating diffusion region is associated with a second conductivity type, the barrier dopant region is associated with the first conductivity type, and the charge drain region is associated with the second conductivity type.