Photoelectric Pixel Well Separation for Signal Linearity
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Solution Overview
Problem
In photoelectric conversion apparatuses, it is challenging to appropriately set the potential of the well shared by transistors, leading to difficulties in maintaining the linearity of signal output due to variations in the on resistance of the selection transistor, which affects the quality of the image produced.
Innovation Solution
The solution involves electrically separating the well of the selection transistor from the well of other transistors, allowing independent control of the potential of the selection transistor's well, thereby reducing the on resistance and maintaining linearity during both on and off states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the selection transistor shares the well with the reset transistor, then the device complexity is reduced, but the manufacturing precision deteriorates due to difficulty in setting the well potential
Solution Approach 1:
The patent divides the well structure into two separate wells: a first well for the selection transistor and a second well for the reset transistor and amplifier transistor. This segmentation allows independent potential control of each well, resolving the contradiction by sacrificing structural simplicity to achieve precise potential control.
Solution Approach 2:
The patent applies different potentials to different wells based on their specific functional requirements. The first well (selection transistor) is set to a first potential while the second well (reset and amplifier transistors) is set to a second potential, allowing each transistor to operate under locally optimized conditions.
2Ease of manufacture
If the selection transistor shares the well with other transistors, then the ease of manufacture is improved, but the reliability deteriorates due to on resistance variations affecting signal linearity
Solution Approach 1:
By segmenting the well structure into separate first and second wells, the patent enables independent potential control that stabilizes the selection transistor's on resistance, thereby maintaining signal linearity and improving reliability.
Solution Approach 2:
The patent changes the potential parameter of the first well independently from the second well. By setting the first well to a first potential and the second well to a second potential, the selection transistor's operating characteristics are stabilized, ensuring consistent signal linearity.
3Manufacturing precision
If independent well potential control is implemented, then the manufacturing precision is improved, but the device complexity increases
Solution Approach 1:
The patent implements independent well potential control by segmenting the well into separate first and second wells, each with independent potential setting capability. This structural segmentation directly enables the desired manufacturing precision.
Solution Approach 2:
The patent applies local quality by providing different potentials to different wells according to their specific functional needs. The first well receives a first potential optimized for the selection transistor, while the second well receives a second potential optimized for the reset and amplifier transistors.
4Ease of operation
If the selection transistor shares the well with other transistors, then the ease of operation is improved, but the reliability worsens due to leakage current affecting image quality
Solution Approach 1:
By segmenting the well structure, the patent reduces leakage current between the selection transistor and other transistors. The separate first and second wells provide electrical isolation that prevents unwanted charge transfer, improving image quality.
Solution Approach 2:
The patent changes the potential parameter of the first well to be different from the second well. This potential difference creates an energy barrier that suppresses leakage current, thereby improving the reliability of image quality.
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 approach effectively suppresses the reduction in linearity, leading to high-quality image acquisition by maintaining a consistent threshold voltage and reducing leakage current, thus enhancing the overall performance of the photoelectric conversion apparatus.
Implementation Method 1
a photoelectric conversion element that generates signal electric charge based on incident light
Data Source
AI summary
A photoelectric conversion apparatus includes an output line and multiple unit pixels. Each of the multiple unit pixels includes a photoelectric conversion element that generates signal electric charge based on incident light, an amplifier transistor that has a gate into which the signal electric charge is input and that outputs a signal based on potential of the gate, a selection transistor with which the amplifier transistor is connected to the output line, and a reset transistor that resets the potential of the gate. The photoelectric conversion apparatus includes a first well on which the selection transistor is provided and a second well on which at least two transistors are provided. The first well is electrically separated from the second well.