Gate-All-Around Photosensor Structure for Smaller Pixels
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Solution Overview
Problem
Current photosensor designs face challenges in miniaturization and improving operation efficiency, particularly in effectively capturing photons and reducing device dimensions while maintaining high image quality.
Innovation Solution
The proposed photosensor structure includes a vertically stacked configuration of n-type doped regions, channel structures, and gate structures, with a vertical transfer gate design that enhances electron pull-out efficiency and switch control, allowing for reduced pixel size and improved image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple photodiodes share the same transfer gate, then device dimension is reduced, but photosensing performance deteriorates
Solution Approach 1:
The transfer gate is segmented into multiple gates (first transfer gate and second transfer gate) that operate independently for different photodiodes. This segmentation allows each gate to be optimized for its specific photodiode while maintaining compact overall device dimensions, resolving the conflict between miniaturization and performance.
Solution Approach 2:
The patent transitions from a planar transfer gate configuration to a vertical stacked configuration where transfer gates are arranged in the vertical dimension above the photodiodes. This dimensional change enables multiple photodiodes to have dedicated transfer gates without significantly increasing the lateral device footprint, thus maintaining miniaturization while improving photosensing performance.
2Use of energy by moving object
If backside illuminated structure is used, then photon reception is improved, but device complexity increases
Solution Approach 1:
The backside illuminated structure is designed to serve multiple functions simultaneously: it enables efficient photon reception while also providing a platform for integrating multiple photodiodes and transfer gates in a compact vertical stack. The shared substrate and common fabrication processes reduce overall device complexity despite the advanced illumination architecture.
3Volume of moving object
If pixel size is reduced for miniaturization, then device dimension is improved, but electron pull-out efficiency deteriorates
Solution Approach 1:
The transfer gates are positioned in the vertical dimension above the photodiodes rather than in the lateral plane. This vertical arrangement allows for adequate gate-to-photodiode spacing and electric field development in the vertical direction, maintaining electron pull-out efficiency even when lateral pixel dimensions are reduced for miniaturization.
Solution Approach 2:
The transfer gates are positioned and configured in advance during fabrication to create optimal electric field distributions before photoelectron generation occurs. This preliminary configuration ensures that when photons are converted to electrons, the electric fields are already in place to efficiently pull out electrons, maintaining high efficiency in miniaturized pixels.
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 achieves a smaller pixel size and enhanced image quality by improving electron pull-out efficiency and switch control, addressing the limitations of existing designs in miniaturization and operation efficiency.
Implementation Method 1
Photosensors, which convert incoming photons into digital signals to realize photosensing
Data Source
AI summary
A photosensor includes a substrate, a photo-detecting column, a gate structure, a floating node structure and a channel structure. The substrate has a first doping type. The photo-detecting column has a second doping type and is disposed in the substrate. The gate structure is disposed on the substrate in a vertical direction, and is electrically insulated from the photo-detecting column. The floating node structure is disposed on the gate structure opposite to the photo-detecting column in the vertical direction, and is electrically insulated from the gate structure. The channel structure extends through the gate structure, is electrically insulated from the gate structure, and is electrically connected to the photo-detecting column and the floating node structure.