Bulk Acoustic Wave Resonator With Insertion Layer for Lateral Wave Reflection
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Solution Overview
Problem
Bulk-acoustic wave resonators face challenges in improving Q performance due to frame resonance and noise issues, particularly in wide band areas, where the frame's inactive area affects kt2 performance and complicates manufacturing processes.
Innovation Solution
A bulk-acoustic wave resonator design featuring a substrate, a membrane layer, a first electrode with a protrusion or inclined portion, a piezoelectric layer, and an insertion layer with a low acoustic impedance material, which enhances reflection efficiency and reduces noise by optimizing the structure to confine resonant energy within the active area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a frame is formed to be thicker than the active area using the same material as the upper electrode, then lateral waves are reflected to confine resonant energy, but kt2 performance deteriorates due to inactive area occupation and noise occurs due to frame resonance
Solution Approach 1:
The frame structure is segmented into multiple functional layers: a first electrode layer for electrical connection, an insertion layer with lower acoustic impedance for wave reflection, and a second electrode layer. This segmentation allows each layer to perform its specific function optimally without the frame occupying excessive active area, thereby maintaining kt2 performance while achieving the desired Q performance through lateral wave reflection.
Solution Approach 2:
The insertion layer acts as an intermediary between the first electrode and the second electrode. This intermediate layer has lower acoustic impedance than the electrode materials, enabling it to effectively reflect lateral acoustic waves while allowing the electrode layers to maintain their electrical functions. The intermediary layer prevents direct interference between the electrode structure and the acoustic wave confinement requirement.
2Object-affected harmful factors
If an eave-shaped structure is used at the outer periphery of the resonator to solve frame problems, then frame resonance and noise are reduced, but the manufacturing process becomes complicated and yield deteriorates
Solution Approach 1:
The invention changes the acoustic impedance parameter of the frame structure by introducing an insertion layer with lower acoustic impedance than the electrode materials. This parameter change enables effective lateral wave reflection and noise reduction without requiring complex eave-shaped geometries. The solution achieves the desired acoustic isolation through material property modification rather than geometric complexity, thereby simplifying the manufacturing process and improving yield.
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 design improves kt2 performance and reduces noise by increasing reflection efficiency of lateral waves, maintaining high performance while simplifying the manufacturing process.
Implementation Method 1
a piezoelectric layer disposed to cover the insertion layer
Implementation Method 2
a bulk-acoustic wave resonator includes: a substrate; a membrane layer forming a cavity with the substrate
Implementation Method 3
an insertion layer including a first portion disposed adjacent to from the end portion of the first electrode and a second portion disposed on an upper portion of the first electrode
Data Source
AI summary
A bulk-acoustic wave resonator includes a substrate; a membrane layer forming a cavity with the substrate; a first electrode at least partially disposed on an upper portion of the cavity including an end portion that is thicker than other portions of the first electrode; an insertion layer including a first portion disposed adjacent to from the end portion of the first electrode and a second portion disposed on an upper portion of the first electrode; a piezoelectric layer disposed to cover the insertion layer; and a second electrode disposed on an upper portion of the piezoelectric layer.