Solid-state imaging pixel connecting transistor threshold control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In solid-state imaging apparatuses, the condition (gate high voltage of FD connecting transistor)−(reset voltage of FD)>(threshold of FD connecting transistor) is often not satisfied, leading to the FD connecting transistor not turning on, resulting in varying reset voltages and incorrect reference voltage reading, which affects the subtraction between light signal voltage and reference voltage.
Innovation Solution
A solid-state imaging apparatus with a connecting transistor that has a lower threshold voltage than the reset transistor, ensuring the FD connecting transistor turns on, and allowing for consistent voltage averaging between adjacent pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the threshold voltage of the FD connecting transistor is high, then the transistor structure is more robust, but the transistor cannot turn on reliably and voltages cannot be averaged
Solution Approach 1:
The patent applies local quality by making the FD connecting transistor have a different threshold voltage characteristic than other transistors in the pixel circuit. Specifically, the FD connecting transistor is designed with a lower threshold voltage to ensure reliable turning on, while other transistors maintain their standard threshold voltages for their respective functions. This localized differentiation resolves the contradiction by allowing the connecting transistor to turn on reliably without requiring changes to the entire circuit design.
Solution Approach 2:
The patent changes the threshold voltage parameter of the FD connecting transistor to be lower than that of other transistors. This parameter change ensures that the condition (gate high voltage of FD connecting transistor)−(reset voltage of FD)>(threshold of FD connecting transistor) is satisfied, allowing the transistor to turn on reliably and average voltages between adjacent pixels, thereby resolving the turning on reliability issue.
2Ease of manufacture
If the threshold voltage of the FD connecting transistor is high, then manufacturing is easier, but voltage averaging fails and reset voltages vary
Solution Approach 1:
The patent applies local quality by differentiating the FD connecting transistor from other transistors through selective ion implantation. The connecting transistor receives additional ion implantation to reduce its threshold voltage, while other transistors maintain their standard fabrication parameters. This localized treatment ensures voltage averaging functionality without requiring complete redesign of the manufacturing process.
Solution Approach 2:
The patent changes the threshold voltage parameter of the FD connecting transistor through additional ion implantation during manufacturing. This parameter change ensures that the transistor can turn on reliably to average voltages between adjacent pixels, thereby achieving consistent reset voltages across the pixel array while maintaining compatibility with standard manufacturing processes.
3Use of energy by moving object
If the FD connecting transistor does not turn on, then power consumption is reduced, but reference voltage reading becomes incorrect
Solution Approach 1:
The patent applies preliminary action by ensuring the FD connecting transistor is pre-configured with a lower threshold voltage through selective ion implantation. This preliminary modification ensures that when the transistor is activated during the reset phase, it turns on reliably to average voltages between adjacent pixels, establishing correct reference voltages before signal reading begins. This prevents reference voltage errors without requiring continuous power consumption.
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 ensures the FD connecting transistor turns on reliably, allowing for accurate reading of reference and signal voltages, improving image signal output and reducing the impact of power supply fluctuations and production variations.
Implementation Method 1
a photoelectric conversion element configured to generate an electric charge by photoelectric conversion
Data Source
AI summary
A solid-state imaging apparatus includes a plurality of pixels, each pixel including: a photoelectric conversion unit; an amplification element; a first signal holding unit and a second signal holding unit arranged on an electric pathway between the photoelectric conversion unit and an input node of the amplification element; a first electric charge transfer unit configured to transfer an electron of the photoelectric conversion unit to the first signal holding unit; and a second electric charge transfer unit configured to transfer an electron held by the first signal holding unit to the second signal holding unit, wherein a voltage supplied to a first control electrode when the electron of the photoelectric conversion unit is transferred to the first signal holding unit is lower than a voltage supplied to a second control electrode when the electron held by the first signal holding unit is transferred to the second signal holding unit.