Bulk Acoustic Resonator Electrode Edge Air Gap for Higher Q
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Solution Overview
Problem
Existing bulk acoustic resonators have limited reflection of transverse sound waves, which affects their Q factor and performance.
Innovation Solution
An electrode structure with an air gap between the dielectric layer and the protrusion/frame metal layer is introduced, along with a fabrication method that includes depositing layers sequentially and forming an air gap at the electrode edge to enhance sound wave reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protrusion structure with certain width is provided at the electrode edge to reflect transverse sound waves, then the sound wave reflection is improved, but the reflected transverse sound wave is still limited and the Q factor cannot be sufficiently improved
Solution Approach 1:
The patent changes the physical parameter of the electrode edge structure by introducing an air gap between the dielectric layer and the protrusion structure. This parameter change (creating a void space) fundamentally alters the acoustic impedance at the edge, enabling much more effective reflection of transverse sound waves compared to the solid protrusion structure alone, thereby significantly improving the Q factor
Solution Approach 2:
The patent creates a composite structure at the electrode edge consisting of the dielectric layer, the air gap, and the protrusion structure. This composite configuration combines materials with different acoustic properties (solid dielectric and air void) to achieve superior sound wave reflection performance that neither component could achieve alone
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 air gap structure effectively reflects transverse sound waves, increasing the Q factor and improving the resonator's performance by binding sound waves within the resonator.
Implementation Method 1
The air gap is formed between the dielectric layer and the protrusion/frame metal layer, and the air gap is located at an electrode edge... effectively reflect the transverse sound wave back to the resonator
Data Source
AI summary
An electrode structure of a resonator and a fabrication method for the electrode structure of the resonator are provided. The electrode structure includes a piezoelectric layer. An electrode metal layer, a dielectric layer, a protrusion/frame metal layer and an etching passivation layer are sequentially arranged above the piezoelectric layer. An air gap is formed between the dielectric layer and the protrusion/frame metal layer, and the air gap is located at an electrode edge. Through the air gap between the dielectric layer and the protrusion/frame metal layer above the piezoelectric layer, an electrode protrusion/frame structure of the resonator with an edge air gap is formed, which serves as an electrode part. When the resonator is working, through the air gap, a transverse sound wave can be reflected back to the resonator and be bound in a resonator body. This greatly increases the Q factor and working performance of the resonator.