Rectangular MEMS Resonator Frame for ESR and Thermal Stability
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Solution Overview
Problem
Existing MEMS resonators face challenges in maximizing equivalent series resistance (ESR) and thermal stability of resonance frequency, which are crucial for frequency reference applications.
Innovation Solution
A silicon microelectromechanical system (MEMS) resonator assembly is designed with four flexural beam elements forming a rectangular frame, connected by coupling elements to maintain a 90-degree angle during vibration, and anchored to mechanical anchors via flexible suspension beams, enabling an in-plane flexural collective resonance mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional quartz crystal oscillators are used for low frequency clock references, then frequency reference functionality is achieved, but cost is high, chip size is large, and robustness against shock and vibrations is poor
Solution Approach 1:
The patent creates a MEMS resonator that copies the frequency reference functionality of quartz crystal oscillators but implements it through a different physical mechanism (mechanical resonance of a beam structure rather than piezoelectric crystal vibration). This allows achieving the same functional outcome with improved robustness and reduced size
Solution Approach 2:
The patent replaces the piezoelectric crystal mechanism with a purely mechanical resonating beam structure actuated by electrostatic forces. This substitution eliminates the fragility of quartz crystals while maintaining the frequency reference function, improving shock and vibration robustness
2Reliability
If ESR is maximized in silicon MEMS resonators, then quality factor Q is improved, but thermal stability of resonance frequency deteriorates
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: beam dimensions (width, thickness, length), material properties (single crystalline silicon), and structural configuration (clamped-clamped beam with specific aspect ratios). These parameter changes are designed to achieve the desired balance between high Q-factor and thermal stability
Solution Approach 2:
The patent employs single crystalline silicon as the resonating beam material, which provides both high mechanical quality factor and favorable thermal properties. The use of single crystalline silicon rather than polycrystalline or amorphous materials contributes to both high Q and improved thermal stability
3Reliability
If a rectangular frame structure with coupling elements is used to maintain 90-degree angles during vibration, then in-plane flexural collective resonance mode is achieved, but device complexity increases
Solution Approach 1:
The resonator is segmented into distinct functional components: the resonating beam element, the coupling elements that maintain geometric constraints, and the anchor structures. This segmentation allows each component to be optimized independently while working together to achieve the collective resonance mode with improved frequency stability
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 proposed resonator assembly achieves optimized ESR and thermal stability, enhancing the quality factor and frequency stability over a wide temperature range, while also reducing the resonator's footprint.
Implementation Method 1
four flexural beam elements forming a rectangular frame... supporting an in-plane flexural collective resonance mode
Data Source
AI summary
A silicon microelectromechanical system, MEMS, resonator assembly, includes four flexural beam elements forming a rectangular frame, each beam element being connected at an end thereof to an end of a neighboring one of the beam elements. The resonator assembly further includes connection elements for connecting the rectangular frame to at least one mechanical anchor, and the resonator assembly supporting an in-plane flexural collective resonance mode.