Bulk Acoustic Wave Resonator Gap Structure for Higher Q
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Solution Overview
Problem
Bulk acoustic wave (BAW) filters face challenges in achieving a high Q factor at resonance and antiresonance points due to increased resistance and lateral wave leakage, especially in high-frequency applications like 5G communications, where thin electrodes are required, leading to complex manufacturing processes and low reflection efficiency.
Innovation Solution
The design incorporates a bulk acoustic wave resonator with a substrate, first and second electrodes, and a piezoelectric layer, featuring a first gap with an inner and outer gap structure that reduces signal loss and energy leakage by varying capacitance, allowing for a high Q factor at both resonance and antiresonance points, achieved through the use of inclined or stepped surfaces and a spacer to manage capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a substantially thin electrode is used to decrease overall thickness for higher frequency operation, then the thickness requirement is met, but resistance increases and Q factor decreases at resonance point
Solution Approach 1:
The invention introduces an air-gap resonator structure with different gap distances at different locations. The first gap has a first distance and the second gap has a second distance greater than the first distance, creating localized capacitance variations that compensate for the thin electrode's high resistance without increasing overall thickness
Solution Approach 2:
The invention changes the physical parameters by introducing controlled air gaps with specific distance relationships. The varying gap distances create different capacitance values that optimize the resonator's Q factor at both resonance and antiresonance points, addressing the performance degradation caused by thin electrodes
2Object-affected harmful factors
If separate structures (frame, air wing, air bridge) are provided to eliminate lateral wave leakage, then wave leakage is reduced, but manufacturing processes become complex and reflection efficiency decreases
Solution Approach 1:
The invention merges the gap structure directly into the resonator body, eliminating the need for separate frame, air wing, or air bridge structures. The first and second gaps are integrated between the piezoelectric layer and electrode, achieving wave leakage control through a unified, simpler structure
Solution Approach 2:
The invention extracts the wave leakage control function from separate peripheral structures and integrates it into the core resonator architecture through the air-gap design, simplifying the overall device while maintaining effectiveness
3Object-affected harmful factors
If separate structures are provided to eliminate lateral wave leakage, then wave leakage is reduced, but reflection efficiency becomes low and Q factor decreases at antiresonance point
Solution Approach 1:
The invention uses localized air gaps with specific distance relationships to control acoustic wave behavior. The first gap with smaller distance and second gap with larger distance create specific capacitance distributions that improve reflection efficiency and Q factor at antiresonance points without requiring complex peripheral structures
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 configuration enhances the Q factor by reducing signal loss and energy leakage, improving reflection efficiency and manufacturing simplicity, enabling effective performance in high-frequency applications without the limitations of conventional designs.
Implementation Method 1
a piezoelectric layer disposed above at least a portion of the first electrode
Implementation Method 2
an air gap is formed above or below a conventional piezoelectric material to serve as a capacitor
Data Source
AI summary
A bulk acoustic wave resonator includes: a substrate; a first electrode disposed above the substrate; a piezoelectric layer disposed above at least a portion of the first electrode; and a second electrode disposed above at least a portion of the piezoelectric layer. A first gap is formed between the piezoelectric layer and one of the first and second electrodes. The first gap includes a first inner gap disposed in an active area of the bulk acoustic wave resonator, and having a first spacing distance between the piezoelectric layer and the one of the first and second electrodes, and a first outer gap disposed outwardly of the active area and having a second spacing distance, different than the first spacing distance, between the piezoelectric layer and the one of the first and second electrodes.