Diagonal Floating Diffusion Sharing for Solid-State Image Sensors
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Solution Overview
Problem
Conventional solid-state image sensing devices face challenges in miniaturization and sensitivity due to the large area occupied by the floating diffusion (FD) portion when multiple photodiode (PD) portions share a common FD, limiting the available space for PD portions.
Innovation Solution
The FD portion is shared diagonally by two photoelectric conversion portions arranged in adjacent rows and columns, allowing for a reduction in the area occupied by the FD and increasing the proportion of photodiode area, with each pair of unit pixels sharing a corresponding FD portion and pixel amplifier transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple photodiode portions share a common floating diffusion portion arranged in parallel, then the number of pixel amplifier transistors is reduced, but the floating diffusion portion occupies a large area
Solution Approach 1:
The patent changes the spatial arrangement of the floating diffusion portion from a parallel configuration to a diagonal configuration relative to the photodiode portions. This dimensional change allows the floating diffusion portion to be shared by multiple photodiodes (e.g., two photodiodes in adjacent rows and columns) without increasing its area, thereby reducing the overall pixel area while maintaining low device complexity
2Area of stationary object
If the floating diffusion portion size is reduced to increase photodiode area proportion, then the photodiode proportion increases, but the floating diffusion portion may not provide sufficient area for signal handling
Solution Approach 1:
By arranging the floating diffusion portion diagonally, the patent achieves a more efficient space utilization that provides sufficient area for both the photodiode portions and the floating diffusion portion. This diagonal arrangement allows multiple photodiodes to share the floating diffusion portion effectively, increasing photodiode area proportion while maintaining adequate signal handling capability
Solution Approach 2:
The patent merges multiple photodiode portions to share a common floating diffusion portion diagonally arranged between them. This merging approach increases the photodiode area proportion while the shared floating diffusion portion maintains sufficient area for reliable signal handling through efficient spatial utilization
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 enables a miniaturized and highly sensitive solid-state image sensing device with a reduced FD area, allowing for a larger photodiode portion area without reducing the overall pixel size, and includes a method for image signal processing to prevent misalignment.
Implementation Method 1
a photoelectric conversion portion which converts the incident light to the pixel signal
Data Source
AI summary
A solid-state image sensing device includes: a plurality of unit pixels 21 arranged in rows and columns each of which outputs a pixel signal according to incident light; and a plurality of floating diffusion portions 22 each of which receives the pixel signals. Each of the floating diffusion portions 22 is shared by two unit pixels 21 which are respectively arranged in adjacent rows and which are respectively adjacent columns.