Optical Sensor Pixel Structure for Low-Noise Photoelectric Detection
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Solution Overview
Problem
Optical sensors using low-temperature polycrystalline silicon face challenges in achieving high-definition and large-area capabilities due to variations in characteristics and high noise levels during signal amplification, particularly in forming thick and uniform p-i-n laminate structures, which affects the detection of photo-electric current.
Innovation Solution
The optical sensor design incorporates a polycrystalline silicon layer for the light-receiving transistor and oxide semiconductor layers for writing/reading transistors, with a light-shielding layer and specific insulating films to reduce off-current and enhance sensitivity, allowing for improved photo-electric current detection and increased sensor area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a thick film of low-temperature polycrystalline silicon is used to increase photo-electric current, then the photo-electric current increases, but it becomes difficult to form a thick and uniform p-i-n laminate structure
Solution Approach 1:
The patent changes the material parameter from low-temperature polycrystalline silicon to oxide semiconductor, which enables formation of thick and uniform films while maintaining low off-current characteristics. This material substitution resolves the contradiction by providing a substance that can be deposited in thick layers with uniform properties, thereby increasing photo-electric current without compromising structural uniformity.
Solution Approach 2:
The patent employs a composite structure combining oxide semiconductor layers with insulating films (such as silicon oxide or silicon nitride) to create a multi-layered p-i-n laminate. This composite approach allows each layer to contribute its optimal properties: the oxide semiconductor provides low off-current and photo-electric activity, while the insulating films provide structural stability and uniformity, collectively resolving the manufacturing precision issue.
2Area of stationary object
If low-temperature polycrystalline silicon is used for large-area sensors, then large-area capability is achieved, but variation in characteristics increases
Solution Approach 1:
The patent changes the material composition from polycrystalline silicon to oxide semiconductor, which inherently exhibits more uniform electrical characteristics across large areas. Oxide semiconductors can be deposited with consistent properties over large substrates, reducing characteristic variation while maintaining large-area capability.
Solution Approach 2:
The patent ensures uniform oxide semiconductor layer formation across the entire sensor area through controlled deposition processes. By maintaining consistent local properties (composition, thickness, crystalline structure) throughout the large-area substrate, the patent reduces overall characteristic variation while preserving large-area functionality.
3Measurement precision
If low-temperature polycrystalline silicon is used, then both large-area and high-definition are possible, but noise during signal amplification becomes large
Solution Approach 1:
The patent changes the semiconductor material from polycrystalline silicon to oxide semiconductor, which possesses inherently lower off-current characteristics. This material parameter change reduces thermal noise and leakage current during signal amplification, thereby reducing noise while preserving high-definition capability.
Solution Approach 2:
The patent employs a photodiode structure with oxide semiconductor that can be optimized for single-use or limited-life applications where low noise is critical. The oxide semiconductor layer acts as a disposable or replaceable component that can be precisely engineered for low-noise performance in each sensor unit.
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 enables the detection of small photo-electric currents with high sensitivity, reduces noise, and increases the resolution and area of the optical sensor by minimizing off-current and variations in transistor characteristics, while allowing extended light exposure for enhanced light reception.
Implementation Method 1
a photodiode... capable of detecting light... a photo-electric current detected by a photodiode
Data Source
AI summary
The optical sensor includes a substrate, a first transistor for functioning as a light-receiving element and a second transistor for writing/reading in a pixel region provided on the substrate. The first transistor is formed by a transistor using polycrystalline silicon, the second transistor is formed by a transistor using an oxide semiconductor. A light-shielding layer is provided on the back side of the oxide semiconductor of the second transistor. Thus, it is possible to irradiate light to the optical sensor fora long time, and in addition to increasing the amount of light received by the first transistor, it is possible to suppress variations in the characteristics of the second transistor.