N-Doped Silicon Micromechanical Resonators With Low Temperature Drift
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Solution Overview
Problem
Silicon-based micromechanical resonators experience high temperature drift due to the temperature dependence of the Young modulus, limiting their applicability and requiring complex and energy-intensive compensation methods, which are not suitable for mass production or battery-operated devices.
Innovation Solution
A micromechanical resonator design featuring an oscillating element made from a silicon wafer with a specific crystal orientation and homogeneous n-type doping, which reduces the temperature variation of the spring constant, allowing for temperature compensation without the need for pn-junctions or diffusion doping, enabling simpler manufacturing and reduced energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active temperature compensation with sensor and control circuitry is used, then temperature drift is reduced, but energy consumption increases and device complexity increases
Solution Approach 1:
The resonator structure itself provides temperature compensation through its geometric design and material selection, eliminating the need for external active control systems. The oscillating element's dimensions and orientation are specifically engineered to exhibit minimal temperature coefficient of frequency, allowing the device to self-regulate its performance across temperature variations without consuming additional energy.
Solution Approach 2:
The invention changes the physical parameters of the oscillating element, specifically its dimensions and orientation relative to the substrate, to achieve inherent temperature compensation. By optimizing the length-to-width ratio and angular orientation, the resonator exploits the anisotropic thermal expansion properties of silicon to cancel out frequency drift, transforming a material limitation into a design advantage.
2Reliability
If active temperature compensation with control circuitry is used, then temperature drift is reduced, but device complexity increases
Solution Approach 1:
The resonator structure itself provides temperature compensation through its geometric design and material selection, eliminating the need for external active control systems. The oscillating element's dimensions and orientation are specifically engineered to exhibit minimal temperature coefficient of frequency, allowing the device to self-regulate its performance across temperature variations without consuming additional energy.
Solution Approach 2:
The invention extracts and eliminates the complex temperature compensation circuitry from the system by implementing compensation at the structural level. The temperature stability function is separated from the electronic control domain and embedded directly into the mechanical resonator design, removing the need for sensors, processors, and control algorithms.
3Reliability
If passive compensation by addition of amorphous SiO2 is used, then temperature drift is reduced, but fabrication complexity increases and resonator performance is compromised
Solution Approach 1:
The invention changes the physical parameters of the oscillating element, specifically its dimensions and orientation relative to the substrate, to achieve inherent temperature compensation. By optimizing the length-to-width ratio and angular orientation, the resonator exploits the anisotropic thermal expansion properties of silicon to cancel out frequency drift, transforming a material limitation into a design advantage.
Solution Approach 2:
The resonator is constructed from homogeneous silicon material throughout, avoiding the need for layered composite structures like amorphous SiO2 coatings. This single-material approach simplifies fabrication by eliminating additional deposition and processing steps while maintaining temperature compensation through geometric design rather than material composition.
4Reliability
If heavy p-type doping is used, then temperature drift is compensated for shear modes, but extensional modes are not well compensated and applicability is limited
Solution Approach 1:
The invention changes the physical parameters of the oscillating element, specifically its dimensions and orientation relative to the substrate, to achieve inherent temperature compensation. By optimizing the length-to-width ratio and angular orientation, the resonator exploits the anisotropic thermal expansion properties of silicon to cancel out frequency drift, transforming a material limitation into a design advantage.
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 design achieves near-zero temperature drift and overcompensation, offering improved design flexibility and performance, particularly for shear, extensional, and torsional modes, while maintaining low noise and energy efficiency, making it suitable for various applications including quartz-based resonator alternatives.
Implementation Method 1
an oscillating element manufactured of a silicon wafer... and comprising an n-type doping agent... The oscillating element is essentially homogeneously doped with said n-type doping agent
Implementation Method 2
excitation means functionally connected to said oscillating element to excite a desired resonance mode of said element
Data Source
Figure 1a~2b
Figure 3a~3b
Figure 4a~4b
AI summary
The invention concerns a micromechanical device and method of manufacturing thereof. The device comprises an oscillating or deflecting element (16) made of semiconductor material comprising n-type doping agent and excitation or sensing means (10, 14) functionally connected to said oscillating or deflecting element (16). According to the invention, the oscillating or deflecting element (16) is essentially homogeneously doped with said n-type doping agent. The invention allows for designing a variety of practical resonators having a low temperature drift.