BAW Resonator Seed-Layer Openings for Higher Q and Lower Acoustic Loss
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Solution Overview
Problem
Existing bulk acoustic wave resonators face challenges in achieving high quality factor and reliability, particularly in thin film bulk acoustic wave resonators, which are essential for high-frequency selectivity and low acoustic loss in wireless communication filters.
Innovation Solution
A method for forming a bulk acoustic wave resonator with a seed layer having an opening, involving the formation of a sacrificial structure, a bottom electrode, a piezoelectric layer, and a top electrode, where the seed layer is etched through a cavity to improve the quality factor and reliability, and the seed layer is selectively removed in the active region to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous seed layer is used in FBAR, then the structure is simpler to manufacture, but the quality factor and reliability are insufficient
Solution Approach 1:
The continuous seed layer is segmented into discontinuous sections by forming openings through the seed layer. This segmentation removes portions of the seed layer that would otherwise interfere with acoustic wave propagation, thereby improving the quality factor while maintaining manufacturing feasibility through standard etching processes
Solution Approach 2:
Specific portions of the seed layer are extracted by forming openings that expose the bottom electrode. This removal of unnecessary seed layer material eliminates acoustic loss pathways and improves resonator performance without requiring complete restructuring of the device
2Reliability
If the seed layer is completely removed to improve performance, then the quality factor improves, but the manufacturing process becomes more complex
Solution Approach 1:
Instead of uniformly removing the seed layer across the entire device, the invention applies local quality changes by creating openings only in specific regions. This selective removal optimizes acoustic performance in critical areas while preserving the seed layer in regions where it provides structural or electrical benefits, thereby balancing performance improvement with manufacturing simplicity
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 approach improves the quality factor and electromechanical coupling coefficient of the bulk acoustic wave resonator, leading to enhanced performance in filters and duplexers, particularly in ladder-type filters, by optimizing the structure and reducing acoustic loss.
Implementation Method 1
a piezoelectric layer is formed on the bottom electrode
Data Source
AI summary
A bulk acoustic wave resonator and a formation method thereof are provided. The method for forming the bulk acoustic wave resonator includes forming a sacrificial structure on a substrate. A seed layer is formed on the sacrificial structure. A bottom electrode is formed on the seed layer. A piezoelectric layer is formed on the bottom electrode. A top electrode is formed on the piezoelectric layer. The sacrificial structure is removed to form a cavity. The seed layer is etched through the cavity.