MEMS Resonator Electrode Shielding for Feed-Through Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Microelectromechanical systems (MEMS) resonators face issues with interfering signals such as induced currents, feed-through currents, and spurious resonance currents, which degrade signal quality, reduce signal-to-noise ratio, and affect frequency stability due to capacitive coupling between drive and sense electrodes and non-active elements.
Innovation Solution
The implementation of resonator electrode shields, made from conductive materials like doped silicon, positioned between non-active elements and drive/sense electrodes to terminate electric field lines, preventing capacitive coupling and reducing interfering signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If drive electrodes are used to generate timing signals in MEMS resonators, then the resonator can function as a timing device, but interfering signals such as induced currents, feed-through currents, and spurious resonance currents are generated that degrade signal quality
Solution Approach 1:
A resonator electrode shield is introduced as an intermediary component between the drive electrode and the resonator structure. The shield is electrically connected to ground and positioned to intercept electric field lines, thereby mediating the interaction between the drive electrode and the resonator to prevent harmful capacitive coupling while allowing the timing signal generation function to proceed
Solution Approach 2:
The harmful capacitive coupling effect is extracted and redirected to the ground through the electrode shield. By providing a dedicated path to ground, the interfering signal paths are separated from the signal path, removing the harmful effect from the timing signal generation process
2Ease of manufacture
If non-active elements are present in the MEMS resonator structure, then the resonator can be manufactured with necessary structural components, but capacitive coupling between drive electrodes and non-active elements creates induced currents that interfere with signal quality
Solution Approach 1:
The electrode shield serves as a mediator between the drive electrode and the non-active structural elements. It intercepts electric field lines that would otherwise couple capacitively to the non-active elements, preventing induced currents while allowing the structural components to remain in place for manufacturing purposes
Solution Approach 2:
The presence of non-active structural elements, which originally caused harmful induced currents through capacitive coupling, is converted into a beneficial situation by introducing the ground-connected shield. The shield provides a controlled path to ground that eliminates the harmful coupling effect while maintaining the structural integrity provided by the non-active elements
3Area of stationary object
If drive and sense electrodes are positioned close to each other for compact design, then device size is reduced, but direct capacitive coupling between electrodes creates feed-through currents that degrade signal integrity
Solution Approach 1:
The electrode shield is positioned between the drive and sense electrodes to intercept electric field lines. This intermediary structure allows the electrodes to remain in close proximity for compact design while the shield blocks the direct capacitive coupling path that would create feed-through currents
Solution Approach 2:
The electrode shield provides localized electromagnetic shielding only in the critical region between the drive and sense electrodes. This allows the overall device to maintain compact dimensions while selectively blocking harmful field interactions in the specific area where drive and sense electrodes are positioned close together
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 approach effectively mitigates the adverse effects of interfering signals, enhancing the quality and stability of timing signals generated by MEMS resonators by ensuring that only active elements interact with the electrodes, thereby improving signal integrity and frequency stability.
Implementation Method 1
positioned between non-active elements and drive/sense electrodes to terminate electric field lines
Implementation Method 2
made from conductive materials like doped silicon
Data Source
AI summary
A microelectromechanical system (MEMS) resonator includes a resonant semiconductor structure, drive electrode, sense electrode and electrically conductive shielding structure. The first drive electrode generates a time-varying electrostatic force that causes the resonant semiconductor structure to resonate mechanically, and the first sense electrode generates a timing signal in response to the mechanical resonance of the resonant semiconductor structure. The electrically conductive shielding structure is disposed between the first drive electrode and the first sense electrode to shield the first sense electrode from electric field lines emanating from the first drive electrode.