Width-Flexural MEMS Resonator for Air Operation

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Solution Overview

Problem

Quartz crystal oscillators are incompatible with integrated circuit fabrication, leading to large size and high costs due to the need for external circuitry, while bulk-mode silicon MEMS resonators require high DC bias voltage and vacuum packaging, complicating integrated circuit design and increasing costs.

Innovation Solution

A width-flexural mode micromechanical resonator that operates in air without the need for vacuum packaging, with a resonating structure anchored to a substrate and configured to flex in a width direction, allowing for reduced air damping and eliminating the requirement for DC bias voltage, thus simplifying integrated circuit design and reducing fabrication costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bulk-mode silicon MEMS resonators are used, then high quality factor is achieved, but high DC bias voltage is required which complicates integrated circuit design

Engineering Contradiction:

Improvequality factorVSAvoidintegrated circuit design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the operational parameters of the MEMS resonator by switching from bulk-mode to width-flexural mode operation. This parameter change allows the resonator to achieve high quality factor without requiring high DC bias voltage, thereby simplifying integrated circuit design while maintaining reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Instead of using the conventional bulk-mode operation that requires high voltage, the patent inverts the approach by using width-flexural mode operation. This inverted approach achieves the desired high quality factor through a different operational mechanism that is compatible with standard integrated circuit voltage levels

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If bulk-mode silicon MEMS resonators are used, then high quality factor is achieved, but vacuum packaging is required which increases fabrication cost

Engineering Contradiction:

Improvequality factorVSAvoidfabrication cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the operational mode from bulk-mode to width-flexural mode, which fundamentally alters the damping characteristics. This parameter change enables the resonator to maintain high quality factor in air without vacuum packaging, significantly simplifying manufacturing and reducing costs

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent extracts the resonator from the vacuum environment requirement by changing its operational mode. The width-flexural mode resonator is designed to operate effectively in air, eliminating the need for vacuum packaging while maintaining high quality factor performance

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

If quartz crystal oscillators are used, then frequency reference accuracy is achieved, but large size and high fabrication cost result due to incompatibility with integrated circuit fabrication

Engineering Contradiction:

Improvefrequency reference accuracyVSAvoidsize and fabrication complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the resonator structure with integrated circuit fabrication processes. By designing the width-flexural mode MEMS resonator to be compatible with standard IC manufacturing, the frequency reference function is integrated directly into the circuit, eliminating the need for separate quartz crystal components and external circuitry

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent creates a silicon-based copy of the resonator function that replaces traditional quartz crystal oscillators. The width-flexural mode MEMS resonator replicates the frequency reference functionality using silicon fabrication techniques, achieving both accuracy and integration compatibility

Inventive Principle:

Principle #26Copying

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 width-flexural mode resonator achieves a high quality factor in air, reducing the need for vacuum packaging and simplifying integrated circuit design, resulting in smaller, more cost-effective frequency reference oscillators for timing and communication devices.

Implementation Method 1

the resonating structure is configured to flex in a flexural mode along a width direction of the resonating structure

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

The resonating structure may be operated in air and thus vacuum packaging may not be required

Methodology Applied

Scientific EffectAir damping: Viscous Damping

Data Source

PatentUS10211805B2Micro-electromechanical resonators and methods of providing a reference frequency

Publication Date: 2019.02.19 AGENCY FOR SCI TECH & RES

AI summary

According to various embodiments, there is provided a micro-electromechanical resonator, including a substrate with a cavity therein; and a resonating structure suspended over the cavity, the resonating structure having a first end anchored to the substrate, wherein the resonating structure is configured to flex in a flexural mode along a width direction of the resonating structure, wherein the width direction is defined at least substantially perpendicular to a length direction of the resonating structure, wherein the length direction is defined from the first end to a second end of the resonating structure, wherein the second end opposes the first end.