BAW Resonator Asymmetry for Overtone-Mode 5G Filtering
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Solution Overview
Problem
Achieving high resonant frequencies (over 6 GHz) in acoustic wave resonators is challenging, leading to issues such as smaller size, lower quality factors, increased edge energy leakage, reduced power handling, and manufacturing difficulties in bulk acoustic wave (BAW) devices.
Innovation Solution
Employing an overtone mode as the main mode in BAW devices by creating structural asymmetry through a thicker passivation layer and asymmetric electrode thicknesses, which excites the overtone mode, allowing for higher resonant frequencies ranging from 5 to 12 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If higher resonant frequencies are achieved in BAW devices, then the device is suitable for 5G New Radio applications, but the quality factor decreases and edge energy leakage increases
Solution Approach 1:
The patent applies asymmetry by making the passivation layer thicker than the piezoelectric layer, creating an asymmetric structure that suppresses spurious modes and reduces edge energy leakage. This asymmetric configuration allows the device to achieve high resonant frequencies (5-12 GHz) while maintaining better quality factor by preventing energy loss at edges through the asymmetric mass loading effect.
2Speed
If higher resonant frequencies are achieved in BAW devices, then the device can filter higher frequency ranges, but manufacturing difficulty increases
Solution Approach 1:
The patent changes the critical parameter of layer thickness ratio, specifically making the passivation layer thicker than the piezoelectric layer. This parameter change enables the device to operate at high frequencies (5-12 GHz) while improving manufacturing yield. The thicker passivation layer provides better process tolerance and reduces sensitivity to thickness variations, thereby easing manufacturing difficulties associated with high-frequency BAW devices.
3Speed
If higher resonant frequencies are achieved in BAW devices, then the device performance is improved, but device yield decreases
Solution Approach 1:
The asymmetric structure with a thicker passivation layer than piezoelectric layer improves device yield by suppressing spurious modes and reducing variability in resonant frequency. This asymmetric design provides better process robustness, allowing high-frequency operation (5-12 GHz) to be achieved with higher manufacturing yield by reducing the impact of thickness tolerances and material variations.
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
BAW devices with an overtone mode exhibit fewer spurious modes, better power handling, higher yield, and are suitable for filtering higher frequency ranges, particularly in 5G New Radio applications, compared to fundamental mode-based devices.
Implementation Method 1
In BAW resonators, acoustic waves propagate in a bulk of a piezoelectric layer
Implementation Method 2
acoustic waves propagate in a bulk of a piezoelectric layer... acoustic reflector
Implementation Method 3
The acoustic wave device is sufficiently asymmetric on opposing sides of the piezoelectric layer over the acoustic reflector such that a main mode of the acoustic wave device is an overtone mode
Data Source
AI summary
Aspects of this disclosure relate to an acoustic wave device having an overtone mode as a main mode. The acoustic wave device is sufficiently asymmetric on opposing sides of a piezoelectric layer over an acoustic reflector such that the main mode of the acoustic wave device is the overtone mode.