MEMS Resonator Layout Modification for Frequency Stability
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Solution Overview
Problem
MEMS resonators face challenges in achieving precise frequency accuracy due to geometric offset caused by non-perfect pattern transfer during fabrication, leading to variations in resonator dimensions and resonance frequency, which cannot be adequately addressed by batch-manufacturing techniques.
Innovation Solution
The design incorporates a bulk-acoustic-mode MEMS resonator with a layout modification feature, such as holes or slits, that compensates for edge position variations, ensuring the resonant frequency remains within desired tolerance limits by making it insensitive to geometric offset through careful modeling and finite element analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If batch-manufacturing techniques are used to fabricate MEMS resonators, then productivity is improved, but manufacturing precision deteriorates due to geometric offset from non-perfect pattern transfer
Solution Approach 1:
The invention changes the physical parameters of the resonator by introducing layout modification features (holes or slits) that alter the resonant frequency in a controlled manner. These features enable compensation for geometric offset by adjusting the effective resonant frequency back to the target value, thus maintaining manufacturing precision while using batch-manufacturing techniques.
Solution Approach 2:
The resonator structure itself contains the layout modification features that automatically compensate for the geometric offset introduced during batch fabrication. The compensation is built into the design, allowing the resonator to self-correct for process variations without requiring external trimming procedures for each individual device.
2Manufacturing precision
If trimming procedures are applied to correct frequency accuracy, then manufacturing precision is improved, but productivity deteriorates due to costly and time-consuming individual processing
Solution Approach 1:
The layout modification features are designed and incorporated into the resonator structure during the initial batch fabrication process. This preliminary design action enables automatic compensation for geometric offset, eliminating the need for subsequent individual trimming procedures and thereby maintaining high productivity while achieving frequency accuracy.
3Manufacturing precision
If resonator dimensions are tightly controlled to achieve frequency accuracy, then manufacturing precision is improved, but device complexity increases due to additional layout features
Solution Approach 1:
The invention introduces layout modification features (holes or slits) at specific local positions within the resonator structure. These localized features selectively modify the resonant frequency without requiring global changes to the entire resonator geometry, thus achieving frequency control with minimal increase in overall device complexity.
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 reduces frequency variations to less than 150 ppm for 50 nm edge position variations, eliminating first-order frequency dependency on geometric offset and maintaining resonance frequency stability across a batch of resonators.
Implementation Method 1
A resonator using this extensional mode, and in which the resonance frequency is determined by a sound wave propagating through the material, is generally known as a bulk acoustic mode resonator
Implementation Method 2
The mechanical resonance frequency of the resonating element should thus be controlled with high precision
Data Source
AI summary
A bulk-acoustic-mode MEMS resonator has a first portion with a first physical layout, and a layout modification feature. The resonant frequency is a function of the physical layout, which is designed such that the frequency variation is less than 150 ppm for a variation in edge position of the resonator shape edges of 50 nm. This design combines at least two different layout features in such a way that small edge position variations (resulting from uncontrollable process variation) have negligible effect on the resonant frequency.