Ge1-xSnx Thermal Sensing Layer for Microbolometer TCR Optimization
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Solution Overview
Problem
Current infrared detecting materials for microbolometers, such as amorphous silicon and vanadium oxide, face limitations in temperature stability and resistance changes, necessitating the development of alternative semiconductor materials with improved resistivity and temperature coefficient of resistance (TCR) properties for enhanced performance.
Innovation Solution
A thermal sensing layer comprising an amorphous Ge1-xSnx film, where 0.17≤x≤0.25, is deposited on a silicon substrate with a silicon dioxide layer, using simultaneous sputter deposition of germanium and tin in an argon atmosphere, achieving compatible resistivity and TCR properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amorphous silicon is used as the infrared detecting material, then the material can be easily integrated into CMOS fabrication process and has high stability, but the temperature coefficient of resistance is limited and requires temperatures to stay below 200°C
Solution Approach 1:
The patent uses vanadium oxide (VOx) thin films as the temperature sensing layer in combination with CMOS readout circuits. VOx materials exhibit metal-insulator phase transitions and have high TCR values, providing enhanced temperature sensitivity while maintaining compatibility with CMOS fabrication processes through careful control of deposition and annealing parameters
2Adaptability or versatility
If vanadium oxide thin films are used, then high TCR and temperature sensitivity are achieved, but temperature restrictions and difficulty in integration into CMOS process occur
Solution Approach 1:
The patent optimizes multiple parameters including deposition temperature, annealing temperature (typically 400-600°C), oxygen partial pressure, and film thickness to achieve the desired VOx phase composition and TCR characteristics. By controlling the oxygen content and crystalline phase, the material achieves high TCR while being compatible with CMOS process temperature constraints
Solution Approach 2:
The patent employs intermediate processing steps such as low-pressure chemical vapor deposition (LPCVD) or atomic layer deposition (ALD) to create buffer layers or modify the VOx surface, facilitating better integration with CMOS structures and improving adhesion while maintaining the high TCR properties
3Adaptability or versatility
If the Ge1-xSnx alloy composition is changed to reduce band gap energy, then different resistivity and TCR properties are achieved, but manufacturing precision control becomes more challenging
Solution Approach 1:
The patent systematically varies the tin content (x parameter) in Ge1-xSnx alloys to tune the band gap energy and achieve desired resistivity and TCR values. By controlling the atomic ratio of Ge to Sn during deposition, the material properties can be optimized for specific microbolometer applications while maintaining manufacturing precision through calibrated deposition parameters
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 Ge1-xSnx thin film exhibits desirable semiconducting behavior with decreased sheet resistance and increased TCR, improving the performance of microbolometers by enhancing their thermal sensing capabilities and compatibility with read-out integrated circuits.
Implementation Method 1
Infrared radiation with wavelengths between 7.5-14 μm strikes the detector material, heating it, and thus changing its electrical resistance
Implementation Method 2
germanium (Ge) and tin (Sn) are simultaneously sputter deposited on the substrate
Data Source
AI summary
The thermal sensing layer for a microbolometer includes a Ge1-xSnx film layer, where 0.17≤x≤0.25. The Ge1-xSnx film layer may be deposited on a substrate layer, such as pure silicon. An additional layer of silicon dioxide may be added, such that the silicon dioxide layer is sandwiched between the silicon substrate and the Ge1-xSnx film, In order to make the Ge1-xSnx thin film layer, germanium (Ge) and tin (Sn) are simultaneously sputter deposited on the substrate, where the atomic ratio of germanium to tin is between 0.83:0.17 and 0.75:0.25 inclusive. The sputter deposition may occur in an argon atmosphere, with the germanium having a deposition rate of 9.776 nm/min, and with the tin having a deposition rate between 2.885 nm/min and 4.579 nm/min.