MEMS Resonator Layout for Stable Resistive Temperature Sensing
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Solution Overview
Problem
Existing MEMS oscillators face challenges in achieving precise temperature measurement and frequency stability due to resistance variations caused by vibrations, particularly in Lamb wave mode and contour vibration modes, leading to noise and reliability issues.
Innovation Solution
A MEMS device with a rectangular plate and holding portions, where the resistive film is formed along a straight line connecting the holding portions, suppressing resistance variations by minimizing amplitude in the long side direction and allowing for accurate temperature measurement through lateral extension vibrating mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistive film is formed on a vibrating structure to measure temperature, then temperature measurement capability is provided, but resistance variations caused by vibrations superimpose noise over temperature variations, degrading measurement precision
Solution Approach 1:
The patent applies local quality by forming the resistive film only in specific regions where vibration amplitude is minimal (nodes or low-amplitude zones) while leaving other regions free to vibrate. This spatial differentiation allows the temperature sensor to remain stable while the resonator maintains its vibration mode, resolving the contradiction between temperature measurement capability and vibration-induced noise.
Solution Approach 2:
The patent introduces an insulating layer as an intermediary between the vibrating structure and the resistive film. This mediator isolates the resistive film from direct mechanical coupling with the vibrating portions, reducing vibration transmission to the temperature sensor while still allowing thermal coupling for accurate temperature measurement.
2Measurement precision
If the holding portions are formed with T-shapes to reduce expansions and contractions, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent employs asymmetric T-shaped holding portions that extend from central areas of opposing sides of the rectangular plate. This asymmetric configuration is specifically designed to minimize expansions and contractions along the straight line connecting the holding portions while maintaining structural integrity and simplicity in fabrication.
3Stability of the object's composition
If a heater is controlled to maintain constant temperature, then frequency stability is improved, but energy consumption increases
Solution Approach 1:
The patent implements a feedback control system where the temperature sensor continuously monitors the temperature of the vibrating structure and provides signals to adjust the heater power accordingly. This closed-loop feedback mechanism maintains constant temperature (and thus frequency stability) while optimizing energy consumption by adjusting heater output based on actual temperature conditions rather than operating at maximum power continuously.
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 enables a highly-precise oscillator with reduced resistance variations and improved temperature measurement accuracy, enhancing the reliability and stability of the MEMS device by minimizing displacement and stress on the insulating layer.
Implementation Method 1
a rectangular plate having short sides and long sides, and including a piezoelectric layer and electrode films above and below the piezoelectric layer, and that receives an input of a driving signal from the exterior
Implementation Method 2
a resistive film is formed upon the insulating layer... serves as a node of extension vibrations
Data Source
AI summary
A MEMS device that suppresses variations in a resistance value caused by contracting vibrations in a direction in which a holding portion extends. The MEMS device includes a frame, a rectangular plate that receives an input of a driving signal, and holding portions that anchor the rectangular plate to the frame. The frame and the rectangular plate are both rectangular in shape. The holding portions are provided extending toward the frame from central areas of the opposing sides of the rectangular plate, and anchor the rectangular plate to the frame. A resistive film is formed in a region that follows a straight line connecting the holding portions that anchor the rectangular plate to the frame and that corresponds to no more than half a maximum displacement from a vibration distribution.