Imaging Pixel Plug Layout for Leakage Current Suppression
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Solution Overview
Problem
Leakage current in imaging devices with charge accumulation regions in semiconductor substrates leads to image quality deterioration due to defects and extended depletion layers.
Innovation Solution
The imaging device design includes a semiconductor substrate with a first and second diffusion region of the same conductivity type, where the second plug has a larger surface area than the first plug, reducing the depletion layer extension and leakage current by minimizing the contact area and impurity concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If charge accumulation regions are provided in the semiconductor substrate, then charge can be accumulated for image sensing, but leakage current occurs leading to image quality deterioration
Solution Approach 1:
The patent applies local quality by making the plug areas asymmetric - the first plug connected to the charge accumulation region has a smaller area than the second plug connected to the diffusion region. This localized differentiation in plug size optimizes the specific region where leakage current occurs (at the charge accumulation region interface) without affecting other regions, thereby suppressing leakage current while maintaining charge accumulation functionality
Solution Approach 2:
The patent changes the geometric parameter of the plugs by setting the area of the first plug to be smaller than the area of the second plug. This parameter modification at the interface between the charge accumulation region and the plug reduces the depletion layer extension and impurity diffusion, effectively suppressing leakage current and improving image quality
2Reliability
If the plug area is increased to reduce contact resistance, then electrical connection is improved, but depletion layer extension increases leading to more leakage current
Solution Approach 1:
The patent applies local quality by differentiating the plug areas based on their specific functions - the first plug (smaller area) connects to the charge accumulation region where leakage suppression is critical, while the second plug (larger area) connects to the diffusion region where lower contact resistance is prioritized. This localized optimization resolves the contradiction between electrical connection quality and depletion layer extension
Solution Approach 2:
The patent employs asymmetry by deliberately making the first plug smaller than the second plug. This asymmetric design allows the first plug to minimize depletion layer extension at the sensitive charge accumulation region interface, while the larger second plug provides sufficient electrical connection at the diffusion region, thus resolving the contradiction between these two requirements
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 effectively suppresses leakage current and improves image quality by reducing the depletion layer extension and impurity diffusion, thereby enhancing the device's performance.
Implementation Method 1
a photoelectric converter that converts light into a charge
Data Source
AI summary
An imaging device including: a photoelectric converter that converts light into a charge; a first diffusion region of a first conductivity type to which the charge is input; a second diffusion region of the first conductivity type; a first plug that has a first surface directly connected to the first diffusion region; and a second plug that has a second surface directly connected to the second diffusion region, where an area of the second surface of the second plug is larger than an area of the first surface of the first plug in a plan view.