Transfer Gate Electrode Surrounding Floating Diffusion Region
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current image sensors face challenges in achieving high efficiency and reduced dark current and white spot phenomena due to surface defects and thermally generated electron-hole pairs, particularly in CMOS image sensors used in various applications.
Innovation Solution
The design incorporates stacked impurity regions with different conductivity types, a floating diffusion region, and a transfer gate electrode with a closed-loop shape that surrounds the floating diffusion region, optimizing charge transmission and storage while minimizing surface defects and dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional image sensor structure is used, then manufacturing is simpler, but dark current and white spot phenomena increase due to surface defects
Solution Approach 1:
The sensor structure is segmented into distinct stacked impurity regions (first and second regions) with different conductivity types and impurity concentrations. This segmentation creates separate functional zones that control charge generation, storage, and transmission, effectively isolating surface defects from affecting the entire sensor structure and reducing dark current and white spot phenomena.
Solution Approach 2:
Different regions of the sensor are assigned different local qualities through varying impurity concentrations and conductivity types. The first impurity region has higher impurity concentration for charge storage, while the second region has lower concentration for charge transmission. This local differentiation optimizes each region's function and reduces the impact of surface defects on overall performance.
2Productivity
If the transfer gate electrode is positioned closer to the photoelectric conversion device, then charge transmission efficiency improves, but surface defects and white spot phenomena increase
Solution Approach 1:
The transfer gate electrode is positioned in the vertical dimension between the first and second impurity regions, rather than only in the horizontal plane. This vertical positioning allows the electrode to be close enough to the photoelectric conversion device for efficient charge transmission while the stacked region structure provides depth separation that isolates surface defects, resolving the contradiction between transmission efficiency and defect reduction.
3Reliability
If the fill factor is increased, then light sensitivity improves, but device area increases
Solution Approach 1:
The stacked impurity region structure utilizes the vertical dimension to enhance charge storage and transmission capabilities. By stacking functional regions vertically rather than expanding horizontally, the design increases light sensitivity through improved charge handling while maintaining a compact footprint, effectively increasing fill factor without proportionally increasing device area.
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 charge transmission efficiency, reduces dark current and white spots, and increases the fill factor of the image sensor by uniformly distributing the electric field and effectively transferring charges from the photoelectric conversion device to the detection device.
Implementation Method 1
an image sensor is a device that converts optical images into electrical signals
Data Source
AI summary
Image sensors are provided. The image sensors may include first and second stacked impurity regions having different conductivity types. The image sensors may also include a floating diffusion region in the first impurity region. The image sensors may further include a transfer gate electrode surrounding the floating diffusion region in the first impurity region. Also, the transfer gate electrode and the floating diffusion region may overlap the second impurity region.