Image Sensor IPO Barrier Structure for Shared Pixel Stability
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Solution Overview
Problem
There is a need for image sensors with a simplified manufacturing process that maintains stable electrical characteristics in shared pixel structures, which are increasingly used in various applications but face challenges in achieving efficient light detection and signal processing.
Innovation Solution
The image sensor design includes a substrate with a floating diffusion region, multiple photodiodes, and an inter-pixel overflow (IPO) barrier that overlaps the floating diffusion region vertically, providing a simplified structure while enhancing electrical stability and sensitivity by allowing excess charge overflow between photodiodes, thus increasing the full well capacity without spatial limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel sizes are miniaturized to increase integration, then productivity and device density improve, but manufacturing precision and electrical characteristics become unstable
Solution Approach 1:
The IPO barrier is positioned at a different vertical level within the substrate, overlapping the floating diffusion region in the vertical direction rather than in the horizontal plane. This three-dimensional arrangement allows the barrier to function without occupying horizontal space, enabling pixel miniaturization while maintaining electrical isolation and stable characteristics
Solution Approach 2:
The IPO barrier is nested within the vertical structure of the pixel, positioned at a specific depth within the substrate and overlapping the floating diffusion region. This nested configuration integrates the barrier function into the existing pixel structure without adding horizontal complexity, supporting miniaturized pixel designs
2Ease of manufacture
If shared pixel structures are used to simplify manufacturing, then ease of manufacture improves, but electrical interference between pixels increases
Solution Approach 1:
By positioning the IPO barrier in the vertical dimension overlapping the floating diffusion region, the patent provides electrical isolation between shared pixels without requiring complex horizontal isolation structures. This allows simplified shared pixel manufacturing while preventing charge overflow and electrical interference between adjacent pixels
Solution Approach 2:
The IPO barrier acts as an intermediary structure between the photodiodes and the floating diffusion region, mediating the electrical interaction. The barrier prevents direct charge overflow between pixels while allowing the shared floating diffusion region to function, thus eliminating electrical interference without complicating the shared pixel structure
3Quantity of substance
If photodiodes are arranged around floating diffusion region to increase capacity, then full well capacity improves, but charge overflow between pixels increases
Solution Approach 1:
The patent extracts the charge containment function from the horizontal pixel boundaries and relocates it to the vertically positioned IPO barrier overlapping the floating diffusion region. This allows photodiodes to be arranged around the floating diffusion region to maximize capacity while the barrier prevents charge overflow between pixels by providing electrical isolation at the critical floating diffusion interface
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 design enables efficient light detection and signal processing with improved sensitivity and color quality, even in reduced pixel sizes, by allowing charge overflow and increasing full well capacity, while simplifying the manufacturing process and reducing electrical interference.
Implementation Method 1
an inter-pixel overflow (IPO) barrier in contact with each of the plurality of photodiodes, the IPO barrier overlapping the floating diffusion region in a vertical direction
Implementation Method 2
a plurality of photodiodes arranged around the floating diffusion region in the sensing area
Data Source
AI summary
An image sensor includes a substrate having a sensing area, a floating diffusion region arranged in the sensing area, a plurality of photodiodes arranged around the floating diffusion region in the sensing area, and an inter-pixel overflow (IPO) barrier in contact with each of the plurality of photodiodes, the IPO barrier overlapping the floating diffusion region in a vertical direction at a position vertically spaced apart from the floating diffusion region within the sensing area.