MEMS Resonator Frequency Tuning via Laser Ablation
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Solution Overview
Problem
Existing methods for manufacturing MEMS resonators often result in frequency splits between the drive and sense axes, leading to inaccuracies and incompatibility with volume manufacturing processes, as they fail to precisely adjust resonant frequencies, which are crucial for the operation of vibrating microelectromechanical devices like gyroscopes.
Innovation Solution
A method involving patterning and etching of the vibrating mass using photoresist or conformal masking materials, followed by laser ablation and deep reactive ion etching to determine and adjust the resonant frequencies by selectively removing mass from specific locations, ensuring precise alignment of resonant frequencies between axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional manufacturing processes are used to fabricate MEMS resonators, then production efficiency is maintained, but resonant frequency precision deteriorates due to frequency splits between drive and sense axes
Solution Approach 1:
The patent applies preliminary action by performing mass removal through laser ablation and etching of sacrificial layers before final device assembly. This allows frequency tuning to be accomplished in advance during manufacturing, ensuring precise resonant frequency matching between drive and sense axes while maintaining compatibility with volume production processes. The preliminary mass removal prevents frequency splits from developing in the final device.
Solution Approach 2:
The patent employs parameter changes by systematically varying the mass of the vibrating structure through controlled removal of material. By changing the mass parameter through laser ablation and etching of sacrificial layers, the resonant frequency is precisely adjusted to eliminate frequency splits. This parameter adjustment is performed while the device is still in the manufacturing process, allowing frequency tuning without compromising production efficiency.
2Manufacturing precision
If electronic or electromechanical correction methods are applied to adjust resonant frequencies, then frequency splits are reduced, but manufacturing complexity increases and precision is insufficient
Solution Approach 1:
The patent applies the taking out principle by extracting the frequency correction function from the operational device and implementing it during manufacturing. Instead of adding complex electronic or electromechanical correction systems to the final device, the method removes the need for such corrections by performing mass adjustment through laser ablation and etching of sacrificial layers during fabrication. This extracts the tuning function to the manufacturing stage, simplifying the final device while achieving precise frequency matching.
3Reliability
If large frequency splits exist in manufactured MEMS resonators, then production tolerances are acceptable, but device accuracy deteriorates and suitability for operation is compromised
Solution Approach 1:
The patent implements feedback by measuring the resonant frequencies of the drive and sense axes after initial fabrication and using this information to guide subsequent mass removal operations. The process involves determining the frequency split, calculating the required mass adjustment, performing laser ablation or etching to remove sacrificial layers, and verifying the frequency matching. This feedback loop ensures that frequency splits are corrected to achieve the precise resonant frequency matching required for reliable device operation.
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 splits, enhances precision, and is compatible with repeatable volume manufacturing processes, improving the accuracy and suitability of MEMS resonators for their intended applications.
Implementation Method 1
removing the photoresist at the mass removal locations using laser ablation
Implementation Method 2
etching the vibrating MEMS device using deep reactive ion etching to remove the mass removal amount of the vibrating MEMS device
Data Source
AI summary
The present invention relates to a method for adjusting the resonant frequencies of a vibrating microelectromechanical (MEMS) device. In one embodiment, the present invention is a method for adjusting the resonant frequencies of a vibrating mass including the steps of patterning a surface of a device layer of the vibrating mass with a mask, etching the vibrating mass to define a structure of the vibrating mass, determining a first set of resonant frequencies of the vibrating mass, determining a mass removal amount of the vibrating mass and a mass removal location of the vibrating mass to obtain a second set of resonant frequencies of the vibrating mass, removing the mask at the mass removal location, and etching the vibrating mass to remove the mass removal amount of the vibrating mass at the mass removal location of the vibrating mass.