Three Level Transfer Gate for Radiation Sensor Pixels
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Solution Overview
Problem
Radiation sensor arrays face challenges with leakage currents and limited dynamic range due to miniaturization, leading to suboptimal image quality and reduced sensor density, as existing solutions either increase sensor size or reduce sensitivity.
Innovation Solution
A method and device for driving radiation sensor pixels using a sensing element, floating diffusion node, and charge storage device, where the transfer gate is biased to multiple voltages to control overflow and collect charges, allowing for high dynamic range imaging without increasing sensor size or reducing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the sensor area is increased to raise saturation limit, then the saturation limit is improved, but the sensor density is reduced
Solution Approach 1:
The patent divides the charge collection system into two separate nodes: a first charge storage node and a second charge storage node. By segmenting the charge storage function across multiple nodes with different capacitances, the system can handle a wider range of charge amounts without requiring a single large sensor area, thus maintaining high sensor density while increasing the effective saturation limit.
Solution Approach 2:
The patent introduces an additional dimension to charge storage by implementing multiple charge storage nodes with different capacitance values rather than relying solely on increasing the physical area of a single node. This dimensional approach to charge storage capacity allows the system to achieve higher saturation limits without proportionally increasing sensor area.
2Object-generated harmful factors
If the sensor area is increased to reduce leakage current, then the leakage current is reduced, but the sensor density is reduced
Solution Approach 1:
By segmenting the charge storage into multiple nodes, the patent reduces the charge burden on each individual node. This segmentation allows each node to operate within optimal charge ranges, reducing the likelihood of saturation-induced leakage currents while maintaining compact sensor area and high density.
Solution Approach 2:
The patent changes the parameter of charge storage capacity by providing multiple nodes with different capacitances. This parameter diversity allows the system to optimize charge distribution and prevent overload conditions that cause leakage, without requiring increased sensor area.
3Quantity of substance
If the dynamic range is increased by adding charge storage capacitors, then the dynamic range is improved, but the device complexity is increased
Solution Approach 1:
The patent segments the charge storage function into multiple nodes with different capacitances, where each node handles specific portions of the charge spectrum. This segmentation achieves extended dynamic range while keeping individual node designs simple and compatible with standard CMOS fabrication, thereby limiting overall device complexity.
Solution Approach 2:
The multiple charge storage nodes serve universal functions: they collectively provide extended dynamic range, enable high sensor density, and maintain compatibility with standard fabrication processes. This multi-functionality approach achieves dynamic range expansion without proportionally increasing device complexity.
4Area of moving object
If the sensor area is reduced to increase sensor density, then the sensor density is improved, but the saturation limit is reduced
Solution Approach 1:
By segmenting charge storage across multiple nodes with different capacitances, the patent enables compact sensor design with high density while maintaining high saturation limits. The segmented architecture allows efficient charge distribution without requiring large individual sensor areas.
Solution Approach 2:
The patent adds a dimensional aspect to charge storage capacity by implementing multiple nodes with varying capacitances rather than relying on physical area expansion. This dimensional approach to charge storage enables high sensor density to coexist with high saturation limits.
5Area of moving object
If the sensitive area is reduced to increase sensor density, then the sensor density is improved, but the sensitivity is reduced
Solution Approach 1:
The patent segments charge storage into multiple nodes that can be optimized for different functions. This segmentation allows the sensitive area to be minimized for high density while charge collection efficiency is maintained through the distributed node architecture, preventing sensitivity loss despite reduced individual node sizes.
Solution Approach 2:
The patent changes the charge storage parameters by providing multiple nodes with different capacitances, which allows optimization of charge collection efficiency independent of sensor area. This parameter optimization maintains sensitivity even as sensor area is reduced for high density.
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 reduces leakage currents and enhances image quality by allowing high dynamic range imaging while maintaining high sensor density and sensitivity, without the need for additional transistors or complex configurations.
Implementation Method 1
a sensing element capable of charge generation as a response to impinging radiation
Data Source
AI summary
A method and device of driving a radiation sensor pixel is disclosed. The sensor pixel comprises a sensing element capable of charge generation as a response to impinging radiation, a floating diffusion node, a transfer gate between the sensing element and the floating diffusion node, and a charge storage device connected to the floating diffusion node via a switch. The method comprises biasing the transfer gate to three or more bias voltages OFF, ON and an intermediate bias between OFF and ON. During the period in which the transfer gate is biased to the intermediate bias, if the sensor reaches saturation, the overflown charges may be collected and part of them stored in the charge storage device, for further analysis and merging.