BAW Piezoelectric Stack Using ALD for High-Frequency Stability
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Solution Overview
Problem
Manufacturing reliable bulk acoustic wave devices with high resonant frequencies is challenging due to issues with mechanical stability, power handling, and edge losses in thinner piezoelectric and electrode layers, which are fragile and prone to stress during post-release processing.
Innovation Solution
A bulk acoustic wave device with a plurality of stacked piezoelectric layers, where at least one layer is formed by atomic layer deposition (ALD) with opposite polarization, and additional layers are formed by sputtering, achieving a thicker piezoelectric stack that increases mechanical stability and power handling while reducing capacitance and edge losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If thinner piezoelectric and electrode layers are used to achieve higher resonant frequencies, then the resonant frequency increases, but the mechanical stability and power handling deteriorate due to fragility and stress during post-release processing
Solution Approach 1:
The piezoelectric layer is divided into multiple thinner layers (first piezoelectric layer, second piezoelectric layer, third piezoelectric layer) with opposite polarizations. This segmentation allows each layer to be thinner for high frequency operation while the stacked configuration provides overall mechanical stability and stress distribution.
Solution Approach 2:
The device uses a composite structure combining multiple piezoelectric layers with opposite polarizations and different materials (AlN, AlScN) to achieve both high resonant frequency and mechanical stability. The composite nature allows optimization of each layer's properties while maintaining overall structural integrity.
2Speed
If thinner piezoelectric and electrode layers are used to achieve higher resonant frequencies, then the resonant frequency increases, but power handling capability deteriorates
Solution Approach 1:
The piezoelectric layer is divided into multiple thinner layers (first piezoelectric layer, second piezoelectric layer, third piezoelectric layer) with opposite polarizations. This segmentation allows each layer to be thinner for high frequency operation while the stacked configuration provides overall mechanical stability and stress distribution.
Solution Approach 2:
The device uses a composite structure combining multiple piezoelectric layers with opposite polarizations and different materials (AlN, AlScN) to achieve both high resonant frequency and mechanical stability. The composite nature allows optimization of each layer's properties while maintaining overall structural integrity.
3Speed
If thinner piezoelectric and electrode layers are used to achieve higher resonant frequencies, then the resonant frequency increases, but edge losses worsen
Solution Approach 1:
The piezoelectric layer is divided into multiple thinner layers (first piezoelectric layer, second piezoelectric layer, third piezoelectric layer) with opposite polarizations. This segmentation allows each layer to be thinner for high frequency operation while the stacked configuration provides overall mechanical stability and stress distribution.
Solution Approach 2:
The device uses a composite structure combining multiple piezoelectric layers with opposite polarizations and different materials (AlN, AlScN) to achieve both high resonant frequency and mechanical stability. The composite nature allows optimization of each layer's properties while maintaining overall structural integrity.
4Stability of the object's composition
If multiple piezoelectric layers with opposite polarizations are stacked to achieve high resonant frequencies, then mechanical stability and power handling improve, but device complexity increases
Solution Approach 1:
The piezoelectric layer is divided into multiple thinner layers (first piezoelectric layer, second piezoelectric layer, third piezoelectric layer) with opposite polarizations. This segmentation allows each layer to be thinner for high frequency operation while the stacked configuration provides overall mechanical stability and stress distribution.
Solution Approach 2:
The device uses a composite structure combining multiple piezoelectric layers with opposite polarizations and different materials (AlN, AlScN) to achieve both high resonant frequency and mechanical stability. The composite nature allows optimization of each layer's properties while maintaining overall structural integrity.
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 enables bulk acoustic wave devices to achieve high resonant frequencies up to 40 GHz with improved mechanical stability and power handling, suitable for 5G New Radio applications, while suppressing non-linearity excitation responses and meeting stringent system level linearity specifications.
Implementation Method 1
The second piezoelectric layer is formed by atomic layer deposition
Implementation Method 2
The third piezoelectric layer can be formed by sputtering
Implementation Method 3
In BAW resonators, acoustic waves propagate in a bulk of a piezoelectric layer
Data Source
AI summary
Aspects of this disclosure relate to method of manufacturing a bulk acoustic wave device. The method can include providing a bulk acoustic wave device structure including a first piezoelectric layer and forming a second piezoelectric layer over the first piezoelectric layer by atomic layer deposition. The second piezoelectric layer can have an opposite polarization relative to the first piezoelectric layer.