Lamb Wave Resonator Dielectric Layout for Spurious Mode Suppression
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Solution Overview
Problem
Current radio frequency front-end resonators, such as SAW and BAW resonators, fail to meet the high frequency, wide bandwidth, and strong power tolerance requirements of 5G communication, while lamb wave resonators offer potential but face challenges in suppressing spurious modes and improving performance.
Innovation Solution
A lamb wave resonator design with a thinned dielectric layer above the interdigital transducer and an acoustic wave reflection layer on the piezoelectric layer, eliminating the need for complex processing and air cavities, and using a dielectric layer as a frequency shift or passivation layer, thereby suppressing spurious modes and enhancing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional dielectric layer structure is used in the lamb wave resonator, then the resonator can be manufactured with standard processes, but plate wave spurious modes (lateral higher-order harmonics) cannot be effectively suppressed and passband flatness deteriorates
Solution Approach 1:
The dielectric layer is segmented into three distinct parts: a first part covering the interdigital transducer, a second part filling the gap between electrode fingers, and a third part on the periphery. This segmentation allows each part to serve different functions - the first part suppresses spurious modes while the other parts maintain standard manufacturing compatibility
Solution Approach 2:
Different regions of the dielectric layer are assigned different thicknesses and positions to achieve local optimization. The first part has specific thickness characteristics for spurious mode suppression, while the second and third parts have different characteristics for maintaining manufacturing standards and overall device performance
2Reliability
If the piezoelectric layer is processed to suppress spurious modes, then plate wave spurious modes can be reduced, but the preparation process becomes complex and yield rate decreases
Solution Approach 1:
The spurious mode suppression function is extracted from the piezoelectric layer and assigned to the dielectric layer instead. This allows the piezoelectric layer to maintain its standard structure and simple processing, while the dielectric layer's specific structure provides the required suppression without adding manufacturing complexity to the piezoelectric layer
Solution Approach 2:
The dielectric layer acts as an intermediary element that provides spurious mode suppression without requiring direct modification of the piezoelectric layer. By placing the functional structure in the dielectric layer, the invention avoids complex piezoelectric layer processing while achieving the same suppression effect
3Reliability
If air cavities are used to suppress spurious modes, then plate wave spurious modes can be reduced, but the device structure becomes complex and manufacturing difficulty increases
Solution Approach 1:
Instead of using complex air cavity structures, the invention employs a simple dielectric layer structure that can be manufactured using standard thin-film deposition processes. This approach replaces complex structural modifications with a simpler, more manufacturable solution that achieves the same suppression function
4Ease of manufacture
If a thick dielectric layer is used above the interdigital transducer, then the resonator can be manufactured with standard processes, but loss increases and performance deteriorates
Solution Approach 1:
The dielectric layer is segmented into multiple parts with different thicknesses and positions. The first part has optimized thickness for low loss, while the second and third parts provide necessary coverage for manufacturing compatibility. This segmentation allows the resonator to achieve both low loss and standard manufacturability simultaneously
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 design improves suppression of lateral higher-order harmonics, reduces loss, and enhances the resonator's performance, making it suitable for 5G frequency bands with improved yield and reduced complexity.
Implementation Method 1
a piezoelectric layer, and an interdigital transducer... The piezoelectric layer is disposed on the substrate
Implementation Method 2
a thickness S2 of a second part that is of the dielectric layer and that is located above the interdigital transducer is thinned, so that plate wave spurious modes such as a lateral higher-order harmonic of an A0 mode and a lateral higher-order harmonic of an S0 mode in the lamb wave resonator can be suppressed
Data Source
AI summary
A filter comprises a lamb wave resonator that includes a substrate, a piezoelectric layer, an interdigital transducer, and a dielectric layer. The piezoelectric layer is disposed on the substrate, and the interdigital transducer and the dielectric layer are disposed on a side of the piezoelectric layer that is distal from the substrate. The interdigital transducer includes a plurality of first electrode fingers and a plurality of second electrode fingers that are alternately arranged in sequence in a first direction. The first direction intersects extension directions of the first and the second electrode fingers. The dielectric layer includes a first part, and the first part is disposed on a surface of the piezoelectric layer and is located on a periphery of the first electrode fingers and the second electrode fingers.