MEMS Resonator Structure With Embedded Oxide for Temperature Stability
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Solution Overview
Problem
The temperature-dependent changes in characteristic parameters of MEMS devices made from single crystal silicon, such as frequency and Young's modulus, affect their performance.
Innovation Solution
Incorporating silicon oxide layers with opposite temperature dependency into the MEMS devices, particularly in the vibrators, to offset temperature-induced deformations and fluctuations by adjusting the mass ratio of silicon and silicon dioxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If single crystal silicon is used for MEMS devices, then mechanical strength and quality factor are improved, but temperature-dependent changes in characteristic parameters occur
Solution Approach 1:
The patent applies composite materials by combining single crystal silicon with silicon oxide layers to form a temperature-compensated structure. The silicon oxide layers are deposited on the silicon substrate and patterned to create regions with different thermal expansion characteristics, forming a composite structure that maintains mechanical strength while compensating for temperature-induced frequency drift through differential thermal expansion between the two materials
Solution Approach 2:
The patent changes physical parameters by controlling the thickness, doping concentration, and geometric patterns of silicon oxide layers on the silicon substrate. By adjusting these parameters, the thermal expansion characteristics of the composite structure are tuned to compensate for the temperature dependence of silicon's resonant frequency, transforming the temperature-stable frequency characteristic through parameter optimization
2Reliability
If dopants are added to single crystal silicon, then electronic band structure changes and temperature dependency is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent segments the temperature compensation function into separate silicon oxide layer regions with different thicknesses or doping concentrations distributed across the silicon substrate. This segmentation allows independent optimization of different regions to compensate for temperature effects without requiring uniform dopant distribution throughout the entire silicon crystal, simplifying the manufacturing process compared to bulk doping approaches
Solution Approach 2:
The patent introduces silicon oxide layers as an intermediary material between the silicon substrate and the external environment. These oxide layers act as a mediator that provides temperature compensation through their own thermal expansion characteristics, eliminating the need for complex dopant diffusion processes and simplifying manufacturing by using standard thin-film deposition techniques
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
Reduces or eliminates temperature-dependent changes in device characteristics, such as frequency fluctuations, by leveraging the contrasting thermal expansion coefficients of silicon and silicon dioxide.
Implementation Method 1
leveraging the contrasting thermal expansion coefficients of silicon and silicon dioxide
Data Source
AI summary
A MEMS device includes a substrate having a front surface and a rear surface, a recess formed in the front surface of the substrate, and a movable electrode and a fixed electrode connected to the substrate and disposed in such a manner as to face each other in the air above the recess. The movable electrode includes an embedded oxide layer embedded in a trench formed in the movable layer. A manufacturing method of a MEMS device includes forming a trench by etching the front surface of the substrate, and forming the embedded oxide layer in the trench by oxidating side surfaces and bottom surface of the trench.