Balanced Electrode Acoustic Wave Resonators for Higher Q Factor
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Solution Overview
Problem
Existing acoustic wave devices face challenges in maintaining high piezoelectric performance and Q factor due to the reduction in piezoelectric coefficient when thinner AlN films are used for higher frequencies, and high dopant concentrations in AlScN films lead to a decrease in the Q factor.
Innovation Solution
The acoustic wave device structure incorporates balanced electrode regions with identical or nearly identical thicknesses and materials for electrode layers and mass loading layers, positioned strategically to enhance the Q factor and maintain high piezoelectric performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If thinner AlN film is used for higher frequencies, then resonant frequency is improved, but piezoelectric coefficient decreases
Solution Approach 1:
The patent changes the material composition parameter by introducing Scandium doping into the AlN piezoelectric layer, transforming it from pure AlN to AlScN. This parameter change allows the film to maintain high piezoelectric coefficient even at thinner dimensions required for higher resonant frequencies.
Solution Approach 2:
The patent creates a composite piezoelectric material system by combining Aluminum Nitride with Scandium dopant, forming AlScN. This composite approach leverages the beneficial properties of both materials to achieve high frequency operation while maintaining strong piezoelectric response.
2Reliability
If high dopant concentrations are used in AlScN film, then piezoelectric coefficient is improved, but Q factor decreases
Solution Approach 1:
The patent applies local quality by using different Scandium doping concentrations in different regions of the piezoelectric layer. The series resonator section uses higher Sc concentration (0.5-2%) to maximize piezoelectric coefficient, while the shunt resonator section uses lower Sc concentration (0.1-0.5%) to preserve Q factor and minimize energy loss.
Solution Approach 2:
The patent segments the piezoelectric layer into distinct regions with different Scandium doping concentrations - one region optimized for piezoelectric performance and another region optimized for low energy loss. This segmentation allows each region to perform its specific function optimally without compromising the other.
3Loss of energy
If mass loading layers are added to improve Q factor, then energy loss is reduced, but device complexity increases
Solution Approach 1:
The patent makes the electrode layers multi-functional by having them serve both as electrical conductors and as mass loading elements. The same electrode structures that provide electrical connectivity also provide the mass loading effect needed to achieve desired resonant frequencies and Q factors, eliminating the need for separate mass loading layers.
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 balanced electrode regions improve the Q factor and maintain high piezoelectric performance, enabling efficient energy transfer and reduced energy loss in acoustic wave devices.
Implementation Method 1
acoustic wave device structures comprising a piezoelectric film and electrodes are utilized in many applications such as surface acoustic wave (SAW) and bulk acoustic wave (BAW) components
Data Source
AI summary
An acoustic wave device structure has first and second electrode layers and a piezoelectric layer extending across series and shunt resonator sections. A piezoelectric layer is positioned between the first and second electrode layers. A first mass loading layer extends across the shunt resonator sections and is positioned between the first electrode layer and the piezoelectric layer. A second mass loading layer extends across the shunt resonator sections and at least one of the series resonator sections. The second electrode layer is positioned between the piezoelectric layer and the second mass loading layer.