Image Sensor Isolation Grid for Higher Quantum Efficiency
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Solution Overview
Problem
CMOS image sensors face challenges in enhancing quantum efficiency and suppressing cross-talk between pixels, which affects their performance in capturing images effectively.
Innovation Solution
Incorporating an isolation structure with a conductive grid overlying the semiconductor substrate, electrically connected to interconnects on both sides, and positioned around photodiodes, which reflects light to prevent cross-talk and enhance quantum efficiency by ensuring incident light is focused on individual pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolation structure with conductive grid is added to reflect light and prevent cross-talk, then quantum efficiency is improved, but device complexity increases
Solution Approach 1:
The isolation structure is segmented into a grid pattern with conductive elements arranged in rows and columns, creating multiple isolated regions that reflect light locally rather than requiring a continuous complex structure throughout the entire sensor
Solution Approach 2:
The conductive grid serves multiple functions simultaneously: it acts as an isolation structure between pixels, a light reflection surface to redirect photons to photodiodes, and an electrical connection path, thereby improving quantum efficiency without proportionally increasing complexity
2Measurement precision
If the conductive grid is positioned around photodiodes to reduce cross-talk, then image quality is improved, but manufacturing precision requirements increase
Solution Approach 1:
The conductive grid is merged with the interconnect structure, combining the isolation function with existing electrical connection pathways, thereby reducing the need for separate precision-aligned components and lowering manufacturing precision requirements
Solution Approach 2:
The conductive grid acts as an intermediary element between the incident light and the photodiode, providing a standardized interface that simplifies alignment requirements by creating a predictable light reflection path without requiring direct precision positioning of multiple components
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
The conductive grid improves image sensor performance by reducing cross-talk and increasing quantum efficiency, leading to better image acquisition and processing capabilities.
Implementation Method 1
the conductive grid and the interconnect are electrically connected to each other. The color filter and the microlens are disposed over the conductive grid and overlapped with the photodiodes
Data Source
AI summary
An image sensor includes a pixel and an isolation structure. The pixel includes a photosensitive region and a circuitry region next to the photosensitive region. The isolation structure is located over the pixel, where the isolation structure includes a conductive grid and a dielectric structure covering a sidewall of the conductive grid, and the isolation structure includes an opening or recess overlapping the photosensitive region. The isolation structure surrounds a peripheral region of the photosensitive region.