Shared Active-Region Pixel Layout for Reduced Image Sensor Pitch
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Solution Overview
Problem
There is a need to reduce the pixel pitch of both rolling blade pixels and global shutter pixels to enable the manufacture of smaller image sensors or those with a higher number of pixels.
Innovation Solution
The solution involves designing an image sensor with first and second pixels, where one or more transistors of the first pixel share an active region with one or more transistors of the second pixel, allowing for a more compact layout by reducing the isolation trenches between adjacent pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transistors of adjacent pixels are completely separated by isolation trenches, then pixel isolation and signal integrity are improved, but pixel pitch and overall sensor size increase
Solution Approach 1:
The patent merges the active regions of adjacent pixels by removing isolation trenches between them, allowing transistors from different pixels to share the same semiconductor region. This consolidation reduces the overall pixel pitch while maintaining functional isolation through careful circuit design and selective isolation trench placement only where absolutely necessary for signal integrity.
Solution Approach 2:
The shared active region serves multiple functions: it acts as the active region for transistors in the first pixel, simultaneously serves as the active region for transistors in the second pixel, and eliminates the need for separate isolation structures. This multi-functionality approach allows the same physical space to support multiple pixel circuits without requiring complete separation.
2Length of moving object
If isolation trenches are reduced or removed between pixels, then pixel pitch is reduced, but risk of signal interference between adjacent pixels increases
Solution Approach 1:
Instead of uniformly isolating all transistor regions, the patent applies isolation selectively only where absolutely necessary for signal integrity. The isolation trench is placed locally between photodiodes rather than completely surrounding each pixel's transistors, providing just enough isolation to prevent harmful interference while minimizing the impact on pixel pitch.
3Reliability
If more transistors are added to each pixel for global shutter functionality, then local storage capability is improved, but pixel area and pitch increase significantly
Solution Approach 1:
The patent combines the transistor circuits of multiple adjacent pixels into shared active regions, allowing global shutter pixels with multiple transistors for local storage to be packed more densely. By merging physical space between pixels, the same pixel area can accommodate the additional transistors needed for global shutter functionality without proportionally increasing overall sensor size.
Data Source
AI summary
The present disclosure relates to an image sensor that includes first and second pixels. One or more transistors of the first pixel share an active region with one or more transistors of the second pixel.