Optical Sensor Transfer Switch LDD Structure Dynamic Range
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Solution Overview
Problem
Current optical sensors and solid-state image pickup devices face challenges in achieving a broader dynamic range, particularly in low-light conditions, leading to higher production costs and complexity in mass production, which affects the uniformity and stability of light sensing characteristics.
Innovation Solution
The use of a MOS transistor with a lightly doped drain (LDD) structure in the transfer switch of the optical sensor, along with a specific semiconductor impurity concentration ratio, allows for a broader dynamic range from one-photon to high-illuminance regions, enabling high sensitivity, speed, and a wide light wavelength band while simplifying the mass production process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a mixed structure of LDD and non-LDD transistors is used to broaden dynamic range, then the dynamic range is improved, but the production cost increases and manufacturing complexity increases
Solution Approach 1:
The patent applies universality by using a single non-LDD transistor structure for all transfer switches in the pixel array, rather than mixing LDD and non-LDD structures. This unified approach allows the same transistor design to serve the function of transferring charges across the entire sensor array, simplifying the manufacturing process while maintaining the broadened dynamic range capability achieved through the dual-capacitor architecture.
Solution Approach 2:
The patent merges the functionality previously requiring separate LDD and non-LDD transistor structures into a single non-LDD transistor type. By combining the transfer switch design into one uniform structure, the patent eliminates the need for multiple fabrication process variants, thereby reducing production cost and manufacturing complexity while preserving the essential charge transfer function.
2Adaptability or versatility
If a mixed structure of LDD and non-LDD transistors is used to broaden dynamic range, then the dynamic range is improved, but the device complexity increases
Solution Approach 1:
The patent applies universality by using a single non-LDD transistor structure for all transfer switches in the pixel array, rather than mixing LDD and non-LDD structures. This unified approach allows the same transistor design to serve the function of transferring charges across the entire sensor array, simplifying the manufacturing process while maintaining the broadened dynamic range capability achieved through the dual-capacitor architecture.
3Adaptability or versatility
If a mixed structure of LDD and non-LDD transistors is used to broaden dynamic range, then the dynamic range is improved, but the uniformity and stability of light sensing characteristic become harder to secure
Solution Approach 1:
The patent applies local quality by optimizing the non-LDD transistor structure specifically for its role as a transfer switch in low-light conditions. By tailoring the transistor characteristics (such as channel dimensions and doping profiles) to the specific requirements of charge transfer in the pixel array, the patent ensures uniform performance across all pixels while maintaining the broadened dynamic range capability.
4Measurement precision
If processing steps are increased to use LDD structure, then the sensitivity is improved, but the productivity decreases
Solution Approach 1:
The patent extracts the LDD structure from the transfer switch design, removing the additional processing steps associated with LDD fabrication. By eliminating this component and its associated manufacturing complexity, the patent maintains sensitivity performance through the dual-capacitor architecture while significantly improving mass production efficiency and reducing fabrication time.
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 results in an optical sensor and solid-state image pickup device that can be mass-produced with a broader dynamic range, high sensitivity, and high speed, contributing to the development of safer and more secure technologies across various markets.
Implementation Method 1
a light receiving element; a storage capacitor configured to store a charge generated by light input to the light receiving element
Data Source
AI summary
One of the problems addressed by the present invention is to provide an optical sensor, a solid-state imaging device, and a signal readout method therefor that greatly contribute to a further development of industry and to the realization of a more secure and safe society. One of the solutions provided by the present invention is an optical sensor comprising a light reception element, a storage capacitor for storing charges, and a transfer switch for transferring, to the storage capacitor, a charge generated by light input into the light reception element. The storage capacitor includes a floating diffusion capacitor and a lateral overflow integration capacitor. The transfer switch is an LDD-MOS transistor of which a drain area has a specific impurity concentration.