MEM Resonator Hole Patterning for Stable Resonant Frequency
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Solution Overview
Problem
Microelectromechanical (MEM) resonators face challenges in achieving a resonant frequency that is insensitive to manufacturing variations, leading to the need for exhaustive post-fabrication screening and laser trimming to ensure high reliability and yield in batch-fabricated devices.
Innovation Solution
A method involving the specification of design parameters for MEM resonators, including a mass suspended above a substrate by anchors, with a pattern of holes designed to compensate for manufacturing uncertainties through parametric computational modeling and iterative optimization to minimize the uncertainty in resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional MEM fabrication processes are used, then manufacturing simplicity is maintained, but resonant frequency precision deteriorates due to sensitivity to manufacturing variations
Solution Approach 1:
The patent applies preliminary action by incorporating compensation features (such as trim structures or adjustable elements) directly into the MEM resonator design before fabrication. This allows manufacturing variations to be compensated for in advance, improving resonant frequency precision without requiring complex post-fabrication adjustments. The compensation mechanism is built into the device structure itself, maintaining fabrication simplicity while achieving better frequency precision.
2Manufacturing precision
If post-fabrication laser trimming is performed, then resonant frequency precision is improved, but manufacturing time and cost increase
Solution Approach 1:
The patent implements self-service by designing the MEM resonator with built-in compensation mechanisms that automatically adjust for manufacturing variations without requiring external trimming operations. The device includes features such as adjustable mass structures or stress compensation elements that can be tuned during standard fabrication processes, eliminating the need for time-consuming laser trimming while maintaining high resonant frequency precision.
3Reliability
If exhaustive post-fabrication screening is conducted, then product reliability is improved, but productivity deteriorates due to increased processing steps
Solution Approach 1:
The patent applies preliminary action by incorporating robustness against manufacturing variations directly into the resonator design before fabrication. This includes designing structures that are inherently less sensitive to dimensional variations or including compensation features that can be adjusted during standard fabrication. By addressing reliability concerns in the design phase rather than through exhaustive post-fabrication screening, the patent maintains high device reliability while preserving fabrication throughput.
Data Source
AI summary
A method is disclosed for the robust fabrication of a microelectromechanical (MEM) resonator. In this method, a pattern of holes is formed in the resonator mass with the position, size and number of holes in the pattern being optimized to minimize an uncertainty Δf in the resonant frequency f0 of the MEM resonator due to manufacturing process variations (e.g. edge bias). A number of different types of MEM resonators are disclosed which can be formed using this method, including capacitively transduced Lamé, wineglass and extensional resonators, and piezoelectric length-extensional resonators.