Laminated Imaging Pixel Structure for Low kTC Noise and Wider Dynamic Range
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Solution Overview
Problem
Laminated imaging devices face challenges in reducing kTC noise and expanding dynamic range due to the presence of metal lines between photoelectric converters and semiconductor substrates, which hinder effective charge transfer and correlated double sampling methods.
Innovation Solution
The imaging device incorporates a pixel structure with a photoelectric converter, amplification transistor, reset transistor, and feedback transistor, along with capacitors and voltage supply circuits, where the reset transistor turns off at a clipping voltage lower than the supply voltage, and the effective thickness of insulating films and dielectric layers are optimized to reduce noise and enhance dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal lines are used between photoelectric converters and semiconductor substrates, then electrical connection is achieved, but charge transfer is hindered and kTC noise increases
Solution Approach 1:
The patent removes the metal line layer between the photoelectric converter and semiconductor substrate, extracting the harmful element that causes kTC noise and charge transfer hindrance. The photoelectric converter is directly connected to the semiconductor substrate without intervening metal lines, eliminating the noise source while maintaining electrical connection.
Solution Approach 2:
The patent introduces an insulating film as an intermediary layer between the photoelectric converter and semiconductor substrate. This mediator enables direct contact and charge transfer while preventing the formation of kTC noise that would occur with metal line intermediaries.
2Adaptability or versatility
If dynamic range is expanded, then imaging performance is improved, but device complexity increases
Solution Approach 1:
The patent employs a reset transistor with voltage-controlled clipping characteristics that dynamically adjusts its operation based on the charge accumulation voltage level. When the voltage reaches the clipping voltage threshold, the transistor automatically turns off, providing dynamic range expansion without requiring complex additional circuitry. This dynamic behavior allows the system to adapt to varying light conditions while maintaining a relatively simple pixel structure.
Solution Approach 2:
The patent utilizes parameter changes in the reset transistor's threshold voltage to achieve different clipping levels. By adjusting the threshold voltage parameter of the reset transistor, the system can control the clipping voltage level, thereby expanding the dynamic range. This parameter-based control avoids the need for complex additional components while achieving versatile imaging performance.
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 reduces kTC noise and expands the dynamic range of the imaging device by improving charge transfer and noise cancellation, while maintaining a simple and efficient pixel structure.
Implementation Method 1
a photoelectric conversion film converting light into a charge
Data Source
AI summary
An imaging device including a pixel including: a photoelectric converter including a first electrode, a second electrode, and a photoelectric conversion film between the first electrode and the second electrode, the photoelectric conversion film converting light into a charge; a first transistor having a first source, drain and gate, the first gate connected to the first electrode; and a second transistor having a second source and drain, one of the second source and the second drain connected to the first electrode and being a charge accumulation region that accumulates the charge. The imaging device further including a first voltage supply circuit supplying a first voltage to the second electrode, where the second transistor has a characteristic that when a voltage of the charge accumulation region is equal to or greater than a clipping voltage, the second transistor is turned off, and the clipping voltage is lower than the first voltage.