FBAR Seed Layer Structure for Higher kt2 Without Q Loss
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Solution Overview
Problem
Film bulk acoustic resonators (FBARs) face a trade-off between increasing the electro-mechanical coupling coefficient (kt2) and maintaining a high quality factor (QF), limiting their bandwidth and data transfer rate in miniaturized wireless communication devices.
Innovation Solution
The introduction of a plurality of seed layers with specific crystalline properties, such as aluminum nitride and titanium, between electrodes in the acoustic resonator, enhances the crystallinity of the piezoelectric layer, thereby improving the kt2 value without compromising the QF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electro-mechanical coupling coefficient (kt2) is increased to enhance bandwidth, then the data transfer rate improves, but the quality factor (QF) decreases
Solution Approach 1:
A buffer layer is introduced as an intermediary between the piezoelectric layer and the substrate. This buffer layer mediates the interaction between the piezoelectric layer and substrate, reducing acoustic wave leakage into the substrate while maintaining the electro-mechanical coupling coefficient. The buffer layer acts as a acoustic impedance matcher that prevents harmful wave propagation without compromising the resonator's coupling performance.
Solution Approach 2:
The acoustic resonator employs a composite structure consisting of multiple layers including the piezoelectric layer, buffer layer, and substrate. This composite material approach allows optimization of each layer's properties to simultaneously achieve high electro-mechanical coupling coefficient and high quality factor. The buffer layer's specific material properties are selected to create the desired acoustic impedance profile.
2Volume of moving object
If miniaturization is pursued to reduce device size, then wireless communication devices become more compact, but manufacturing precision requirements increase
Solution Approach 1:
The invention optimizes the thickness parameters of the piezoelectric layer and buffer layer to achieve miniaturization while maintaining performance. By carefully controlling the thickness of these thin films within specific ranges, the resonator achieves compact size without sacrificing the electro-mechanical coupling coefficient or quality factor. The parameter optimization allows standard manufacturing processes to achieve the required precision.
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
This approach increases the kt2 value of the acoustic resonator, enhancing its performance and bandwidth, while maintaining a high quality factor, thus improving data transfer rates in miniaturized wireless communication devices.
Implementation Method 1
a piezoelectric layer disposed between the first electrode and the second electrode
Implementation Method 2
a plurality of seed layers disposed on one side of the resonating part
Data Source
AI summary
An acoustic resonator and a method of manufacturing the same are provided. The acoustic resonator includes a resonating part including a first electrode, a second electrode, and a piezoelectric layer; and a plurality of seed layers disposed on one side of the resonating part.