Solid-State Imaging Device Transfer Gate Floating Diffusion Integration
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Solution Overview
Problem
In solid-state imaging devices, the reduction of pixel size necessitates enhanced charge transfer efficiency, but the layout restrictions due to the vertical gate surrounding the floating diffusion make it difficult to minimize the device area while maintaining efficient charge transfer.
Innovation Solution
A solid-state imaging device design featuring a transfer gate with a columnar shape and an opening in the vertical direction, allowing the floating diffusion unit to be formed extending into the region surrounded by the opening, eliminating the need for contacts between the floating diffusion and the transistor, and enabling shared diffusion layers and transistors across multiple pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vertical gate surrounds the floating diffusion to enhance charge transfer efficiency, then charge transfer efficiency is improved, but device area increases due to layout restrictions requiring contacts and metal layers
Solution Approach 1:
The floating diffusion unit and the diffusion layer of the transistor are merged into a single integral structure. This eliminates the need for separate contacts and metal layers to connect them, thereby reducing device area while maintaining efficient charge transfer through the vertical gate structure
Solution Approach 2:
The floating diffusion unit serves dual functions: it acts as both the charge collection node and the source diffusion layer for the transistor. This multi-functionality eliminates the need for separate dedicated contact structures, reducing overall device area while preserving charge transfer efficiency
2Reliability
If the floating diffusion is connected to the transistor via contact and metal layer, then electrical connection is established, but device area increases due to additional layout requirements
Solution Approach 1:
The floating diffusion unit and transistor diffusion layer are combined into one integral structure, eliminating the need for separate contact and metal layer connections. This direct integration maintains reliable electrical connection while significantly reducing the area occupied by interconnection structures
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 reduces the device area while improving charge transfer efficiency by eliminating the need for contacts and allowing shared components, thereby enhancing the overall performance of the imaging device.
Implementation Method 1
a photoelectric conversion unit that produces a charge according to incident light
Data Source
AI summary
There is provided a solid-state imaging device that includes a photoelectric conversion unit, a transfer gate, a floating diffusion unit, and a transistor. The photoelectric conversion unit produces a charge according to incident light. The transfer gate has a columnar shape having an opening that is continuous in a vertical direction, and transfers the charge from the photoelectric conversion unit. The floating diffusion unit is formed extending to a region surrounded by the opening of the transfer gate, and converts the transferred charge into a voltage signal. The transistor is electrically connected to the floating diffusion unit via a diffusion layer.