Bulk Acoustic Wave Resonator Pad Layout for Lower Connection Resistance
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Solution Overview
Problem
Bulk acoustic wave filters face challenges with high connection resistance, especially at higher frequencies, which affects insertion loss and roll-off characteristics, necessitating a reduction in electrode thickness and resistance.
Innovation Solution
A bulk acoustic wave resonator design incorporating a conductive thin film and pads with specific overlapping regions and distances to increase electrode thickness and create a discontinuous acoustic impedance region, reducing connection resistance and improving the quality factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electrode thickness is reduced to increase operating frequency, then the operating frequency increases, but the connection resistance increases
Solution Approach 1:
The invention extends the electrode structure from a single-layer thin film to a multi-layer stacked configuration. By adding a first electrode layer and a second electrode layer in vertical stacking with overlapping regions, the effective conduction path is extended in the vertical dimension while maintaining thin horizontal profiles. This dimensional transition allows high operating frequency (thin electrode) to coexist with low connection resistance (multi-layer stacking effect).
Solution Approach 2:
The invention employs composite electrode structures where multiple electrode layers with different materials or properties are stacked together. The first electrode layer and second electrode layer form a composite conductive system that leverages the advantages of each layer, achieving both high frequency operation and reduced connection resistance through material composition optimization.
2Speed
If the electrode thickness is reduced to increase operating frequency, then the operating frequency increases, but the insertion loss increases
Solution Approach 1:
The multi-layer stacked electrode structure extends conduction pathways vertically, creating additional parallel conduction channels. This dimensional expansion reduces electrical resistance without compromising the thin-film high-frequency characteristics, thereby reducing insertion loss while maintaining high operating frequency.
Solution Approach 2:
The first electrode layer and second electrode layer are merged through overlapping regions to form a unified conductive system. This merging creates extended effective electrode areas and multiple conduction paths, reducing overall resistance and insertion loss while preserving the thin-film resonator's high-frequency operation.
3Speed
If the electrode thickness is reduced to increase operating frequency, then the operating frequency increases, but the roll-off characteristics worsen
Solution Approach 1:
The vertical stacking of electrode layers creates a more confined acoustic field with improved boundary definition. This dimensional structuring enhances the resonator's frequency selectivity and sharpness, improving roll-off characteristics while maintaining high operating frequency through thin-film design.
Solution Approach 2:
The composite electrode structure with multiple layers provides better acoustic impedance matching and field confinement. This composite configuration enhances the resonator's frequency discrimination capability, resulting in improved roll-off characteristics alongside high-frequency operation.
4Reliability
If the active region area is increased to reduce connection resistance, then the connection resistance decreases, but the acoustic wave reflection decreases
Solution Approach 1:
The invention resolves this contradiction by transitioning from horizontal area expansion to vertical layer stacking. The overlapping regions of the first and second electrode layers provide extended conduction paths vertically, reducing connection resistance without increasing the horizontal active region footprint, thereby preserving acoustic wave reflection performance.
Solution Approach 2:
The electrode structure employs local quality variation where the overlapping regions provide enhanced conduction specifically at connection points, while the non-overlapping regions maintain acoustic reflection properties. This localized functional differentiation allows simultaneous optimization of connection resistance and acoustic reflection without compromising either.
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 effectively reduces connection resistance and insertion loss while maintaining the active region's effectiveness, enhancing the performance of bulk acoustic wave filters and duplexers.
Implementation Method 1
the piezoelectric film vibrates due to the inverse piezoelectric effect and generates sound waves that propagate in a direction perpendicular to the electrode surface
Implementation Method 2
sound waves that propagate in a direction perpendicular to the electrode surface and are reflected at the upper and lower interfaces
Data Source
AI summary
The present disclosure provides a bulk acoustic wave resonator, a manufacturing method thereof, and a filter, wherein the bulk acoustic wave resonator includes: a substrate; an acoustic reflection unit on the substrate; a piezoelectric stack structure on the acoustic reflection unit; and a pad on the piezoelectric stack structure; wherein the pad has an overlapping region with the acoustic reflection unit. The acoustic wave resonator, the manufacturing method thereof and the filter of the present disclosure can effectively reduce connection resistance of the bulk acoustic wave resonator, thereby reducing insertion loss of the filter.