X-ray detector phototransistor pixel yield
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Solution Overview
Problem
Conventional X-ray detectors using photodiodes face challenges with low process yield and high manufacturing costs due to complex manufacturing processes and noise characteristics.
Innovation Solution
The X-ray detector incorporates a unit pixel area with a phototransistor and a storage capacitor instead of a photodiode, facilitating a larger area process and improving manufacturing yield and cost efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a photodiode is used in the unit pixel area, then the light detection function is achieved, but the process yield is low and manufacturing cost is high
Solution Approach 1:
The patent changes the fundamental parameter of the light-sensitive element from photodiode to phototransistor. This parameter change enables the use of standard thin film transistor manufacturing processes, significantly improving process yield and reducing manufacturing costs while maintaining light detection functionality.
Solution Approach 2:
The patent copies the successful thin film transistor structure and manufacturing process from display technology and applies it to the X-ray detector. By using the same TFT fabrication process for both the switching transistor and the phototransistor, the patent achieves high yield and low cost production.
2Reliability
If a photodiode with P-I-N stacking structure is used, then light detection is achieved, but the manufacturing process becomes complex and yield decreases
Solution Approach 1:
The patent changes the structural parameter from complex P-I-N stacking to a planar TFT structure with photodetector integration. This simplifies the manufacturing process by using standard TFT fabrication steps including photolithography, thin film deposition, and etching, thereby improving yield and reducing complexity.
Solution Approach 2:
The patent segments the unit pixel area into distinct functional regions: the phototransistor region for light detection, the storage capacitor region for charge storage, and the TFT region for signal readout. This segmentation allows each component to be manufactured using optimized processes and simplifies the overall fabrication.
3Measurement precision
If a photodiode is used, then the unit pixel area is compact, but the signal sensing sensitivity is reduced
Solution Approach 1:
The patent merges the light detection function and the signal amplification function into a single phototransistor device. The phototransistor's inherent gain mechanism amplifies the photocurrent signal, improving sensing sensitivity without requiring additional separate components, thus maintaining compact pixel area.
Solution Approach 2:
The patent utilizes the vertical dimension by implementing multi-layered electrode structures and stacked capacitor configurations. This allows increased capacitance and improved signal storage capability within the same planar footprint, effectively enhancing sensitivity without expanding the pixel area.
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 enhances the photodetection characteristics and signal sensing sensitivity, reducing manufacturing costs and improving the overall process yield.
Implementation Method 1
a phototransistor that is turned on by a reset signal applied to the first gate line, the phototransistor connected to another end of the storage capacitor and providing a charge generated by an incident light source
Data Source
AI summary
The present disclosure relates to an X-ray detector. The X-ray detector includes the first and second gate lines arranged to be spaced apart from each other on a substrate, a data line and a bias line that are arranged to be spaced apart from each other in a direction intersecting the first and second gate lines, and define a unit pixel area, a storage capacitor that is arranged in the unit pixel area and has one end connected to a ground, a phototransistor that is turned on by a reset signal applied to the first gate line and provides a signal generated by an incident light source to the storage capacitor, and a thin film transistor that is turned on by a gate signal applied to the second gate line to provide a charge stored in the storage capacitor to the data line.