Mono-crystalline Silicon Active-Pixel Sensor for High-Speed X-Ray Detection
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Solution Overview
Problem
Passive flat panel detectors using amorphous silicon thin-film transistors in medical X-ray applications suffer from low read-out speed and noise performance due to high parasitic capacitances and on-resistances, while active-pixel sensors on mono-crystalline silicon offer improvements but are costly.
Innovation Solution
A semiconductor device with an integrated active-pixel array on a mono-crystalline wafer, coupled with readout circuit chips and electric connections, forming a wafer-scale imaging sensor that enhances performance and reduces production costs by using CMOS or NMOS/PMOS transistors and featuring solder balls or wires for connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive flat panel detectors with amorphous silicon thin-film transistors are used, then manufacturing cost is reduced, but read-out speed and noise performance deteriorate due to high parasitic capacitances and on-resistances
Solution Approach 1:
The detector is divided into two functional segments: an active-pixel sensor array integrated on a mono-crystalline silicon wafer for high-speed signal readout, and a separate scintillator layer for X-ray to light conversion. This segmentation allows each component to be optimized independently, with the mono-crystalline silicon providing low parasitic capacitance and high transconductance for fast readout, while the scintillator handles the X-ray detection function.
Solution Approach 2:
The patent merges the advantages of both amorphous silicon and mono-crystalline silicon technologies by combining an active-pixel sensor array (integrated circuitry on mono-crystalline wafer) with a scintillator layer. This hybrid approach combines the low cost and ease of manufacture of amorphous silicon processes with the superior electrical performance of mono-crystalline silicon transistors, achieving both cost-effectiveness and high read-out speed.
2Ease of manufacture
If passive flat panel detectors with amorphous silicon thin-film transistors are used, then manufacturing cost is reduced, but noise performance deteriorates due to high parasitic capacitances and on-resistances
Solution Approach 1:
The detector is divided into two functional segments: an active-pixel sensor array integrated on a mono-crystalline silicon wafer for high-speed signal readout, and a separate scintillator layer for X-ray to light conversion. This segmentation allows each component to be optimized independently, with the mono-crystalline silicon providing low parasitic capacitance and high transconductance for fast readout, while the scintillator handles the X-ray detection function.
Solution Approach 2:
The patent merges the advantages of both amorphous silicon and mono-crystalline silicon technologies by combining an active-pixel sensor array (integrated circuitry on mono-crystalline wafer) with a scintillator layer. This hybrid approach combines the low cost and ease of manufacture of amorphous silicon processes with the superior electrical performance of mono-crystalline silicon transistors, achieving both cost-effectiveness and high read-out speed.
3Speed
If active-pixel sensors on mono-crystalline silicon are used, then read-out speed and noise performance are improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to mono-crystalline silicon for the active-pixel sensor array, which fundamentally improves transistor performance including transconductance and parasitic capacitance. This parameter change enables high read-out speed and low noise performance while the integrated circuit design and wafer-level manufacturing keep costs manageable.
Solution Approach 2:
The active-pixel sensor array integrates multiple functions within each pixel element, including photodetector, transistor, and signal processing circuitry, all fabricated on the same mono-crystalline silicon wafer. This integration allows the device to serve multiple functions self-sufficiently, reducing the need for additional external components and assembly steps, thereby controlling manufacturing cost despite using premium mono-crystalline silicon.
4Reliability
If active-pixel sensors on mono-crystalline silicon are used, then noise performance is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to mono-crystalline silicon for the active-pixel sensor array, which fundamentally improves transistor performance including transconductance and parasitic capacitance. This parameter change enables high read-out speed and low noise performance while the integrated circuit design and wafer-level manufacturing keep costs manageable.
Solution Approach 2:
The active-pixel sensor array integrates multiple functions within each pixel element, including photodetector, transistor, and signal processing circuitry, all fabricated on the same mono-crystalline silicon wafer. This integration allows the device to serve multiple functions self-sufficiently, reducing the need for additional external components and assembly steps, thereby controlling manufacturing cost despite using premium mono-crystalline silicon.
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
The solution improves read-out speed and noise performance while reducing production costs, offering a more efficient and cost-effective imaging system compared to amorphous silicon solutions and conventional wafer-scale detectors.
Implementation Method 1
A scintillator converts X-radiation into visible light, which is then converted by means of photodiodes and readout circuits into a digital code
Implementation Method 2
A scintillator converts X-radiation into visible light
Data Source
AI summary
The assembly comprises a semiconductor device with an active-pixel array, a readout circuit chip or plurality of readout circuit chips mounted outside the active-pixel array, the readout circuit chip or plurality of readout circuit chips being configured to read out voltages or currents provided by the active-pixel array, and electric connections between the active-pixel array and the readout circuit chip or plurality of readout circuit chips.