Acoustic Wave Resonator Reinforcement at Piezoelectric Cavity Edges
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cracks may occur in the piezoelectric layer of acoustic wave devices, particularly around cavity portions where no electrode is provided, leading to reduced device performance.
Innovation Solution
Incorporating a reinforcing film that overlaps the boundary between regions where the piezoelectric layer and cavity portion overlap and do not overlap, using a support substrate with a dielectric film and a cavity portion open to the piezoelectric layer side, to reduce or prevent cracks in the piezoelectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cavity portion is provided in a support member, then device complexity is reduced and Q values are improved, but cracks occur in the piezoelectric layer around the cavity portion
Solution Approach 1:
A reinforcing film is introduced as an intermediary element between the piezoelectric layer and the cavity portion. This film specifically reinforces the region where the piezoelectric layer overlaps the outer wall of the cavity portion, preventing crack propagation while maintaining the acoustic wave device's Q values and performance characteristics
2Area of stationary object
If the number of electrode pairs is reduced, then device area is reduced, but resonance characteristics and Q values deteriorate
Solution Approach 1:
The reinforcing film is applied locally only to specific regions where the piezoelectric layer overlaps the cavity portion's outer wall, rather than uniformly across the entire device. This localized reinforcement prevents cracks in critical areas while maintaining resonance characteristics, allowing for reduced electrode pairs and smaller device area without sacrificing Q values
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 effectively reduces or prevents cracks in the piezoelectric layer, enhancing the device's resilience and maintaining resonance characteristics even when the number of electrode pairs is reduced, thus maintaining high Q values and fractional bandwidth.
Implementation Method 1
a piezoelectric layer that includes lithium niobate or lithium tantalate and is provided in a first direction, which is a thickness direction of the support substrate
Implementation Method 2
an interdigital transducer (IDT) electrode provided in the first direction of the piezoelectric layer and including a first busbar and a second busbar that face each other
Data Source
AI summary
An acoustic wave device includes a support including a support substrate, a piezoelectric layer extending in a first direction, which is a thickness direction of the support substrate, an IDT electrode provided in the first direction of the piezoelectric layer and including first and second busbars facing each other, first electrode fingers each including a base end connected to the first busbar, and second electrode fingers each including a base end connected to the second busbar, and a reinforcing film provided in the first direction of the piezoelectric layer. The support includes a cavity open to the piezoelectric layer side in the first direction, and the reinforcing film overlaps at least a portion of a boundary between a region where the piezoelectric layer and the cavity overlap and a region where the piezoelectric layer and the cavity do not overlap in a plan view in the first direction.