Shared-Pixel Image Sensor Structure for Isolation-Free TR Layout
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Solution Overview
Problem
Existing image sensors with shared pixel structures face challenges in maximizing photodiode area and minimizing noise due to the need for isolation areas between transistor sets, which reduces the area available for photodiodes and increases noise levels.
Innovation Solution
The image sensor employs a shared pixel structure where each shared pixel includes multiple photodiodes that share a floating diffusion area, and the corresponding transistor sets are arranged in a mirror symmetry structure, allowing them to share a source region of a selection transistor, thereby eliminating the need for isolation areas between transistor sets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation areas are provided between transistor sets, then electrical isolation is improved, but photodiode area is reduced
Solution Approach 1:
Adjacent transistor sets share a common source region, merging previously separate isolation areas into a shared resource. This eliminates the need for duplicate isolation structures between transistor sets, increasing photodiode area while maintaining electrical isolation through the shared source region's inherent potential difference
Solution Approach 2:
The shared source region serves multiple functions: it acts as the source for both transistor sets simultaneously and provides electrical isolation between them through potential differences applied to different gates. This multi-functionality eliminates the need for separate isolation areas
2Object-generated harmful factors
If isolation areas are provided between transistor sets, then noise interference is reduced, but photoelectric conversion efficiency is reduced
Solution Approach 1:
By merging isolation areas into a shared source region, the patent increases the photodiode area available for photoelectric conversion while maintaining noise isolation through electrical potential control, thereby improving photoelectric conversion efficiency without sacrificing noise reduction
3Measurement precision
If pixel size is reduced, then resolution is improved, but photodiode area per pixel is reduced
Solution Approach 1:
Multiple pixels share common transistor sets and isolation areas, allowing smaller pixel pitch while maintaining adequate photodiode area. The shared resources reduce the overhead per pixel, enabling higher resolution without proportionally reducing photodiode 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 increases the area of the photodiode per unit shared pixel and reduces noise by eliminating the need for isolation areas, thereby enhancing the photoelectric conversion efficiency and reducing noise sources such as flicker noise and dark current.
Implementation Method 1
each of the plurality of unit pixels includes one photodiode
Data Source
AI summary
This disclosure relates to image sensors and electronic apparatuses including the same. An image sensor including: a pixel area including shared pixels, wherein each of the shared pixels includes at least two photodiodes that form a group and share a floating diffusion (FD) area; and a transistor (TR) area adjacent to the pixel area, wherein the TR area includes transistor sets corresponding to the shared pixels, wherein, when a first shared pixel and a second shared pixel are arranged adjacent to each other in a first direction, a first TR set corresponding to the first shared pixel and a second TR set corresponding to the second shared pixel share a source region of a first selection TR.