MEM Resonator Hole Layout for Frequency Variation Compensation
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Solution Overview
Problem
Microelectromechanical (MEM) resonators face significant 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 geometric modifications) directly into the MEM resonator design before fabrication. This allows the resonant frequency to be pre-compensated for expected manufacturing variations, reducing the need for post-fabrication adjustments and improving frequency precision without significantly complicating the fabrication process.
Solution Approach 2:
The patent employs parameter changes by modifying geometric parameters of the MEM resonator (such as mass distribution, anchor configurations, or cavity dimensions) to create designs that are less sensitive to manufacturing variations. By optimizing these parameters, the resonant frequency becomes more robust against process variations, achieving better precision without requiring complex fabrication steps.
2Manufacturing precision
If post-fabrication laser trimming is applied, then resonant frequency precision is improved, but manufacturing time and cost increase
Solution Approach 1:
The patent eliminates the need for post-fabrication laser trimming by incorporating compensation features directly into the resonator design. This preliminary compensation approach achieves the required frequency precision during the fabrication process itself, allowing for batch production without individual trimming operations, thereby maintaining high productivity and throughput.
Solution Approach 2:
The patent implements self-service by designing MEM resonators with inherent compensation mechanisms that automatically compensate for manufacturing variations without requiring external intervention. The built-in compensation features allow the devices to self-adjust or self-correct for process variations, eliminating the need for time-consuming post-fabrication trimming operations and enabling high-volume production.
3Reliability
If exhaustive post-fabrication screening is performed, then device reliability is improved, but manufacturing time and cost increase
Solution Approach 1:
The patent performs preliminary reliability assurance by incorporating compensation features and robust design elements that pre-mitigate the effects of manufacturing variations. This approach ensures that devices meet reliability specifications directly from the fabrication process, eliminating or reducing the need for exhaustive post-fabrication screening and allowing for faster production cycles with maintained reliability.
Solution Approach 2:
The patent enables devices to self-ensure reliability through built-in compensation mechanisms that automatically counteract manufacturing variations. This self-service approach reduces variability in device performance, allowing for higher yields and reduced screening requirements while maintaining high reliability standards across production batches.
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.