Mg-Ta Doped AlN Piezoelectric Body for Lower-Cost MEMS
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Solution Overview
Problem
Scandium-doped aluminum nitride is expensive, leading to higher production costs for piezoelectric bodies, and the validity of tantalum valence in existing numerical calculations is questionable.
Innovation Solution
A piezoelectric body of aluminum nitride doped with magnesium and tetravalent tantalum, represented by Al1-X-YMgXTaYN, with specific ratios of X and Y, and a higher content of tetravalent tantalum, enhancing performance indices d33, g33, and K2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If scandium-doped aluminum nitride is used to achieve high piezoelectric constant, then the piezoelectric performance is improved, but the production cost increases significantly
Solution Approach 1:
The patent replaces expensive scandium with cheaper magnesium and tantalum dopants. The use of abundant elements like Mg and Ta instead of rare earth elements like Sc directly addresses the cost issue while maintaining piezoelectric functionality through alternative doping mechanisms.
Solution Approach 2:
The patent changes the chemical composition parameters by introducing specific doping ratios of Mg and Ta (with Ta in +4 oxidation state). By controlling the doping concentrations and oxidation states, the patent achieves high piezoelectric constants without relying on expensive scandium, thus resolving the cost-performance contradiction.
2Ease of manufacture
If aluminum nitride is doped with magnesium and tantalum based on numerical calculation, then the piezoelectric body can be produced, but the validity of tantalum valence is suspect and performance is uncertain
Solution Approach 1:
The patent incorporates specific feedback mechanisms through characterization techniques (XPS, XANES, TEM-EELS) to verify the oxidation state of tantalum. This feedback loop ensures that the tantalum is indeed in the +4 state, confirming the validity of the numerical calculations and ensuring predictable high piezoelectric performance.
Solution Approach 2:
The patent performs preliminary characterization and validation of the doping process before final production. By pre-confirming the oxidation state and structural properties through advanced spectroscopy and microscopy, the patent ensures that subsequent production batches will consistently achieve the desired performance, eliminating uncertainty.
3Reliability
If tetravalent tantalum is incorporated into aluminum nitride doped with magnesium, then the piezoelectric performance index is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The patent controls the oxidation state parameter of tantalum to be specifically +4, which is the key to achieving high piezoelectric performance. By maintaining this specific parameter during manufacturing (through controlled atmosphere processing and optimized sintering conditions), the patent achieves enhanced performance without excessive complexity, as the parameter control is integrated into the existing manufacturing workflow.
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
The proposed piezoelectric body achieves higher performance indices, enabling high-frequency operation with lower loss and wider bandwidth, reducing production costs and improving device compactness and power efficiency.
Implementation Method 1
Devices utilizing the piezoelectric phenomenon have been used in various fields. These devices have been used with increasing frequency in portable devices
Data Source
AI summary
Provide are a nitride piezoelectric body having a value indicating a performance index (at least any one of d33, g33, and K2) higher than that of aluminum nitride not doped with any element, and a MEMS device using the same. The nitride piezoelectric body is a piezoelectric body represented by chemical formula Al1-X-YMgXTaYN, wherein X+Y is less than 1, X is in a range of more than 0 and less than 1, and Y is in a range of more than 0 and less than 1, and Ta includes tetravalent tantalum.