Stacked Solid-State Imaging Device Ground Potential Control
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Solution Overview
Problem
Solid-state imaging devices face challenges in increasing saturation capacitance while maintaining transistor reliability and avoiding hot carrier emission due to large transistor size requirements and increased potential differences.
Innovation Solution
A solid-state imaging device is designed with multiple substrates, each having distinct ground potentials and thinner gate oxide films, connected via metal, allowing for a stacked structure that optimizes signal conversion and reduces wiring distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the ground potential of a pixel is reduced to increase potential difference in the pixel, then the saturation capacitance of the photodiode is increased, but the transistor size must be increased to withstand the applied potential difference, occupying a large area
Solution Approach 1:
The imaging device is divided into multiple substrates: a first substrate containing the photodiode and a second substrate containing the transistor. This segmentation allows the photodiode to operate at a reduced ground potential for increased saturation capacitance, while the transistor resides on a separate substrate where it can withstand the applied potential difference without occupying excessive area in the same layout plane.
Solution Approach 2:
The solution transitions from a two-dimensional planar layout to a three-dimensional stacked configuration. By stacking the first substrate (photodiode) and second substrate (transistor) vertically, the patent enables independent optimization of each component's electrical characteristics without lateral area constraints, allowing the photodiode to achieve higher saturation capacitance while the transistor maintains compact dimensions.
2Quantity of substance
If the potential difference applied to the pixel transistor is increased to increase saturation capacitance, then the saturation capacitance is improved, but the reliability may decrease or hot carrier emission may occur
Solution Approach 1:
By segmenting the device into separate substrates, the patent isolates the high potential difference stress to the transistor substrate where it can be managed through appropriate transistor design and material selection, while the photodiode substrate operates at reduced potential for high saturation capacitance. This segmentation prevents hot carrier emission in the photodiode while maintaining transistor reliability through dedicated transistor substrate design.
Solution Approach 2:
The patent introduces an intermediate structure between the photodiode and transistor, including charge transfer mechanisms and potential isolation layers, that mediates the interaction between the two components. This intermediary allows the photodiode to operate at reduced ground potential for increased saturation capacitance while preventing harmful high potential differences from directly stressing the transistor, thus maintaining reliability.
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 enhances imaging performance by maintaining transistor reliability and reducing the area occupied by transistors, while enabling efficient signal conversion and image processing.
Implementation Method 1
at least a light receiving element that outputs a signal based on the intensity of received light
Data Source
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AI summary
[Problem] To control the ground potential of an imaging device composed of stacked semiconductors. [Solution] A solid-state imaging device includes a first substrate and a second substrate. The first substrate includes at least a light receiving element that outputs a signal based on the intensity of received light, and the ground potential is a first ground potential. The second substrate includes at least a transistor that outputs a signal based on a signal output from the light receiving element, and the ground potential is a second ground potential different from the first ground potential.