Out-of-Phase Flexural Micro-Mechanical Resonator for Low-MHz Timing
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Solution Overview
Problem
Existing quartz crystal oscillators (XOs) face challenges in scaling down their size and volume to meet the increasing density of electronic devices, and micro-mechanical resonators like BAW and capacitive MEMS resonators have limitations in achieving low MHz resonant frequencies and efficient power usage.
Innovation Solution
The development of micro-mechanical resonators that operate in out-of-plane flexural modes, with multiple portions extending from a base and configured to resonate out-of-phase, allowing for lower resonant frequencies and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If quartz crystal oscillators are used to achieve good frequency accuracy and low noise, then timing signal quality is improved, but device area and volume cannot scale down to meet increasing electronic density requirements
Solution Approach 1:
The patent replaces traditional quartz crystal oscillators with micro-mechanical resonator copies that replicate the timing function. These resonators use piezoelectric materials to generate mechanical vibrations at precise frequencies, providing similar timing accuracy in a much smaller footprint that can scale with electronic density requirements
2Speed
If BAW resonators operate in GHz range with good piezoelectric coupling, then resonant frequency is improved, but multiple divider stages are required increasing cost and power consumption
Solution Approach 1:
The patent changes the resonant frequency parameter of the micro-mechanical resonator from GHz range to low MHz range by adjusting the physical dimensions and mass of the resonating structure. This eliminates the need for multiple frequency division stages, thereby reducing power consumption and device complexity while maintaining good piezoelectric coupling efficiency
3Speed
If BAW resonator thickness is increased to lower resonant frequency to low MHz range, then operating frequency is improved, but manufacturing becomes impractical requiring 1000× film thickness
Solution Approach 1:
Instead of lowering frequency by increasing thickness in the vertical dimension (which makes manufacturing impractical), the patent achieves low MHz resonant frequencies by increasing the lateral dimensions and mass of the resonating structure. This dimensional approach maintains manufacturability while achieving the desired frequency range
4Speed
If capacitive MEMS resonators operate at low MHz frequencies, then resonant frequency is improved, but nanometer scale gaps make fabrication challenging and electromechanical coupling is lower increasing power consumption
Solution Approach 1:
The patent replaces the capacitive transduction mechanism with piezoelectric transduction. This substitution eliminates the need for precise nanometer-scale gaps between capacitive plates, simplifying fabrication. The piezoelectric effect directly couples electrical signals to mechanical vibrations, providing stronger electromechanical coupling and lower power consumption at low MHz frequencies
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
This solution enables micro-mechanical resonators to achieve resonant frequencies below a few MHz, reducing the need for multiple divider stages, which in turn decreases cost and power consumption for timing applications.
Implementation Method 1
A bulk acoustic wave (BAW) resonator is an example of a micro-mechanical resonator that includes a suspended or anchored piezoelectric portion, which generates micro-acoustic waves
Implementation Method 2
The first resonator portion is configured to operate in an out-of-plane flexural mode that displaces at least part of the first resonator portion out of the first plane. The second resonator portion is configured to operate in an out-of-plane flexural mode that displaces at least part of the second resonator portion out of the second plane and out-of-phase relative to the first resonator portion
Data Source
AI summary
A method comprises: forming a die including a cavity; coupling an anchor to the die; coupling a first resonator to a side of the anchor, in which the first resonator is suspended over the cavity and is operable to bend towards or away from a bottom of the cavity; and coupling a second resonator to the side of the anchor, in which the second resonator is suspended over the cavity, at least a part of the first resonator is laterally between the side of the anchor and a part of the second resonator, and the first resonator is operable to bend in an opposite direction from the second resonator.