Bulk Acoustic Wave Filter Frequency Tuning via Intermediary Structure
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Solution Overview
Problem
The complexity of tuning resonance frequencies in bulk acoustic wave filters increases fabrication difficulties and affects performance, particularly due to the need for precise thickness adjustments of top electrodes, which complicates the manufacturing process and may impact device characteristics.
Innovation Solution
A method involving the formation of a sacrificial epitaxial structure mesa on a compound semiconductor substrate, followed by the deposition of insulating and piezoelectric layers, and etching to create cavities, allowing for precise adjustment of the frequency tuning structure's thickness to tune the resonance frequency of the bulk acoustic wave resonance structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the resonance frequency is tuned by adjusting the thickness difference of top electrodes, then the resonance frequency difference can be controlled, but the fabrication complexity increases and device performance may be affected
Solution Approach 1:
The patent introduces a frequency tuning structure as an intermediary element positioned between the bulk acoustic wave resonance structure and the substrate. This mediator enables frequency tuning through its thickness parameter without requiring direct modification of the top electrode thickness, thereby simplifying the fabrication process while maintaining precise resonance frequency control capability
Solution Approach 2:
The patent separates the frequency tuning function from the main resonance structure by creating a distinct frequency tuning structure with controllable thickness. This segmentation allows independent optimization of the resonance structure and the tuning mechanism, reducing fabrication complexity while preserving frequency control precision
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 approach simplifies the frequency tuning process, enhances performance by reducing fabrication complexity, and allows for precise control of resonance frequencies, thereby improving the characteristics of bulk acoustic wave filters.
Implementation Method 1
forming a piezoelectric layer on the bottom electrode layer
Implementation Method 2
polishing the insulating layer by a chemical-mechanical planarization process
Implementation Method 3
etching the sacrificial epitaxial structure mesa to form a cavity
Data Source
AI summary
A bulk acoustic wave filter comprises a substrate, an insulating layer disposed on the substrate and having a first cavity and a second cavity formed therein, a first bulk-acoustic-wave-resonance-structure disposed on the first cavity and a second bulk-acoustic-wave-resonance-structure disposed on the second cavity. The first bulk-acoustic-wave-resonance-structure comprises a first bottom electrode disposed on the first cavity, a first top electrode disposed on the first bottom electrode, a first piezoelectric layer portion sandwiched between the first top electrode and the first bottom electrode, and a first frequency tuning structure disposed between the first cavity and the first bottom electrode. The second bulk-acoustic-wave-resonance-structure comprises a second bottom electrode disposed on the second cavity, a second top electrode disposed on the second bottom electrode, a second piezoelectric layer portion sandwiched between the second top electrode and the second bottom electrode.