Bulk Acoustic Wave Resonator Cavity Structure for Higher Q
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Solution Overview
Problem
Current bulk acoustic wave resonators face challenges in improving the quality factor (Q value) due to issues with charge accumulation and mechanical support, leading to radio frequency loss and degraded performance.
Innovation Solution
The design incorporates a cavity boundary structure with a bilayer configuration, including a boundary layer and a dielectric support layer, and a charge accumulation preventing layer to avoid conductive channels, enhancing mechanical support and reducing radio frequency loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer cavity boundary structure is used, then the device complexity is low, but the mechanical support is insufficient leading to low quality factor
Solution Approach 1:
The cavity boundary structure is divided into two distinct layers: a first dielectric layer providing mechanical support and a second dielectric layer with different acoustic impedance. This segmentation allows each layer to perform its specific function optimally, improving the quality factor while maintaining manageable structural complexity
Solution Approach 2:
The cavity boundary structure uses composite material configuration with two different dielectric layers having distinct acoustic impedance values. This composite approach enhances mechanical support and acoustic performance, resolving the contradiction between structural complexity and quality factor improvement
2Reliability
If a uniform dielectric material is used throughout the cavity boundary, then the manufacturing is simple, but charge accumulation occurs creating conductive channels and RF loss
Solution Approach 1:
Different dielectric materials are used in different regions of the cavity boundary structure. The first dielectric layer uses a material with first acoustic impedance while the second dielectric layer uses a material with second acoustic impedance. This local differentiation prevents charge accumulation and eliminates conductive channels, improving RF performance while remaining manufacturable
3Strength
If the cavity boundary structure is simplified, then the manufacturing precision requirements are reduced, but the mechanical support strength decreases
Solution Approach 1:
The cavity boundary structure is segmented into a first dielectric layer specifically designed for mechanical support and a second dielectric layer for acoustic optimization. This segmentation allows the first layer to be optimized for strength without compromising manufacturing precision, as each layer has a dedicated function
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 improves the quality factor and performance of the resonator by increasing mechanical support and preventing charge accumulation, resulting in better filter performance.
Implementation Method 1
a piezoelectric layer, located on a side of the carrier substrate in a second direction perpendicular to the main surface of the carrier substrate; a first electrode and a second electrode, disposed on opposite sides of the piezoelectric layer in the second direction
Implementation Method 2
a cavity boundary structure, disposed between the carrier substrate and the piezoelectric layer in the second direction, wherein the cavity boundary structure has a body part and a protruding part, the body part extends along the first direction, and the protruding part protrudes from the body part along the second direction away from the carrier substrate and toward the piezoelectric layer
Implementation Method 3
a periphery dielectric layer, located on a side of the protruding part of the cavity boundary structure away from the resonant cavity, and between the body part of the cavity boundary structure and the piezoelectric layer, a material of the periphery dielectric layer is different from a material of at least a portion of the protruding part adjacent to the periphery dielectric layer
Data Source
AI summary
A bulk acoustic wave resonator is provided. The bulk acoustic wave resonator incudes a carrier substrate, having a main surface extending along a first direction; a piezoelectric layer, located on a side of the carrier substrate in a second direction perpendicular to the main surface of the carrier substrate; a first electrode and a second electrode; a cavity boundary structure, having a body part extending along the first direction and a protruding part protruding from the body part toward the piezoelectric layer; a resonant cavity, defined by the cavity boundary structure and the piezoelectric layer; and a periphery dielectric layer, located on a side of the protruding part of the cavity boundary structure away from the resonant cavity, a material of the periphery dielectric layer is different from a material of at least a portion of the protruding part adjacent to the periphery dielectric layer.