V-Groove Shear-Mode Acoustic Wave Filter for Stable 5G Bandwidth
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Solution Overview
Problem
Current acoustic wave filters, such as SAW and BAW filters, face limitations in extending to higher frequency bands like LTE high and 5G, suffer from low coupling coefficients, and are prone to warping and excessive center frequency variability, making them unsuitable for commercial use.
Innovation Solution
A shear-mode acoustic wave filter is formed on V-shaped grooves of a [100] crystal orientation Si layer over a substrate, incorporating a first metal layer, a thin-film piezoelectric layer, and a second metal layer in an interdigitated pattern or sheet, with customizable groove angles to enhance coupling coefficients and reduce frequency variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If SAW filters are used for low/mid LTE bands, then they are suitable for current mobile bands, but they cannot be extended to LTE high and 5G bands
Solution Approach 1:
The patent changes the physical parameters of the filter structure by transitioning from surface acoustic wave (SAW) to bulk acoustic wave (BAW) mode, and further to shear-mode BAW with V-groove topography. This parameter change enables the filter to operate at higher frequencies (LTE high and 5G bands) while maintaining commercial usability through improved coupling coefficients and frequency stability.
Solution Approach 2:
The patent introduces a vertical dimension by creating V-shaped grooves in the substrate and forming piezoelectric layers that extend into these grooves. This dimensional change from planar to three-dimensional structure enables enhanced acoustic wave confinement and improved coupling coefficients necessary for high-frequency operation.
2Manufacturing precision
If BAW filter center frequency is determined by thin-film piezoelectric layer thickness, then frequency can be controlled, but integrating multiple frequencies requires repeated masking and thinning causing tolerance and cost degradation
Solution Approach 1:
The patent segments the piezoelectric structure into multiple layers with different orientations and properties. By using segmented layers rather than a single thick layer, the design achieves multiple frequency responses while simplifying the manufacturing process and reducing the need for repeated masking and thinning operations.
Solution Approach 2:
The patent employs composite piezoelectric structures with multiple layers having different crystal orientations and material properties. This composite approach enables frequency tuning through material composition rather than solely through thickness control, reducing manufacturing complexity and improving tolerance.
3Adaptability or versatility
If Lamb-wave filters are used, then they are theoretically promising for high frequencies, but they have unacceptable low coupling coefficient precluding commercial use
Solution Approach 1:
The patent utilizes bulk acoustic wave vibration modes in a shear-mode configuration rather than Lamb-wave modes. By exciting shear-horizontal (SH) acoustic waves through the V-groove structure, the patent achieves significantly higher coupling coefficients while maintaining high-frequency operation capability, making the device commercially viable.
Solution Approach 2:
The patent converts the typically harmful effect of acoustic wave leakage into a beneficial feature by using the V-groove boundaries to confine and guide the shear-horizontal acoustic waves. This converts what would be energy loss into enhanced acoustic confinement and improved coupling coefficients.
4Ease of manufacture
If known acoustic wave filters are used, then they can be manufactured, but they are susceptible to warping/buckling and excessive center frequency variability
Solution Approach 1:
The patent applies local quality enhancement by creating V-grooves with specific geometries and orientations at critical locations beneath the piezoelectric layers. This localized structural modification provides mechanical support and stress relief exactly where needed, preventing warping and buckling while maintaining ease of manufacture through standard semiconductor fabrication processes.
Solution Approach 2:
The patent uses curved V-shaped groove profiles rather than sharp angular grooves. This curvature provides stress distribution that prevents buckling and warping of the thin-film structures, improving frequency stability while remaining compatible with standard manufacturing processes.
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 solution achieves a higher coupling coefficient, larger bandwidth, and reduced beam bending variability, enabling the shear-mode acoustic wave filter to operate effectively across multiple frequencies with improved stability and commercial viability.
Implementation Method 1
forming a shear-mode acoustic wave filter over the V-shaped grooves, the shear-mode acoustic wave filter including a first metal layer, a thin-film piezoelectric layer, and a second metal layer
Implementation Method 2
forming a set of V-shaped grooves in a [100] crystal orientation Si layer over a substrate; and forming a shear-mode acoustic wave filter over the V-shaped grooves
Data Source
AI summary
Methods of forming a shear-mode acoustic wave filter on V-shaped grooves of a [100] crystal orientation Si layer over a substrate and the resulting devices are provided. Embodiments include forming a set of V-shaped grooves in a [100] crystal orientation Si layer over a substrate; and forming a shear-mode acoustic wave filter over the V-shaped grooves, the shear-mode acoustic wave filter including a first metal layer, a thin-film piezoelectric layer, and a second metal layer, wherein the second metal layer is an IDT pattern or a sheet.