BAW Resonator Edge Frame Structure for Transverse Wave Reflection
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Solution Overview
Problem
Existing bulk acoustic wave resonators face challenges in controlling the transverse length of air gaps, which affects the improvement of quality factor (Q value) and parallel resonance impedance (Rp value), leading to difficulties in optimizing insertion loss performance.
Innovation Solution
A bulk acoustic wave resonator design featuring an electrode edge frame structure with a laminated structure including an edge convex layer and passivation layer, forming cantilever and convex structures that create controlled gaps to reflect transverse waves back into the resonator, thereby reducing energy loss and enhancing impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the transverse length of air gap is not accurately controlled, then the manufacturing process is simple, but the quality factor and parallel resonance impedance cannot be improved
Solution Approach 1:
The electrode edge frame structure is divided into multiple functional components: a convex structure for defining the air gap position, a cantilever member for forming the air gap, and a passivation layer for coverage. This segmentation allows precise control of the transverse length of the air gap through the convex structure's dimensions while maintaining manufacturing feasibility through standardized fabrication processes.
Solution Approach 2:
The electrode edge frame structure applies local modifications only at the edge regions of the electrode layer, rather than modifying the entire structure. The convex structure and cantilever member are positioned specifically at the edges to create the air gap, while the central resonator structure remains unchanged. This localized approach enables precise control of air gap dimensions without complicating the overall device manufacturing.
2Reliability
If the electrode edge frame structure is added to control transverse waves, then the quality factor and parallel resonance impedance are improved, but the device complexity increases
Solution Approach 1:
The electrode edge frame structure merges multiple functions into a single integrated component system: the convex structure serves as both a mechanical support and a template for air gap formation, the cantilever member simultaneously provides structural continuity and defines the air gap dimension, and the passivation layer offers both electrical isolation and mechanical protection. This merging reduces the need for separate components and simplifies the manufacturing process while achieving the desired improvement in quality factor and parallel resonance impedance.
Solution Approach 2:
The convex structure acts as an intermediary element between the electrode layer and the air gap region. It provides a controlled interface that defines the air gap's transverse length without requiring direct manipulation of the air gap itself during manufacturing. This intermediary structure enables precise control of the air gap dimensions through standard thin-film deposition and patterning processes, improving reliability without proportionally increasing device complexity.
3Reliability
If the cantilever member extends beyond the electrode layer edge, then the air gap is formed for wave reflection, but the manufacturing precision requirements increase
Solution Approach 1:
The convex structure is formed first as a preliminary feature that defines the intended position and dimensions of the air gap. The cantilever member is then deposited and patterned to extend from the electrode layer edge to the convex structure, with the convex structure serving as a pre-established reference for alignment. This preliminary action ensures that the cantilever member's positioning is guided by an already-formed feature, reducing the actual manufacturing precision requirements compared to defining the air gap position through a single-step process.
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 electrode edge frame structure effectively increases the parallel resonance impedance and quality factor, improving the resonator's insertion loss performance by accurately controlling the size of the convex structure and reflecting transverse waves, thus reducing energy loss.
Implementation Method 1
a piezoelectric layer; an electrode layer located at both sides of the piezoelectric layer
Implementation Method 2
reflecting transverse waves back into the resonator, thereby reducing energy loss
Data Source
AI summary
A bulk acoustic wave resonator and a bulk acoustic wave filter are provided. The bulk acoustic wave resonator includes: a piezoelectric layer; an electrode layer located at both sides of the piezoelectric layer; and an electrode edge frame structure located at an edge of the electrode layer and located at one side of the electrode layer away from the piezoelectric layer. The electrode edge frame structure includes a laminated structure, the laminated structure includes an edge convex layer and a passivation layer laminated in a longitudinal direction, and the passivation layer is located at one side of the edge convex layer away from the piezoelectric layer; in a transverse direction, the laminated structure includes a cantilever member and a convex structure connected with each other; a cantilever gap is arranged between the cantilever member and at least one of the piezoelectric layer and the electrode layer.