Bulk Acoustic Wave Resonator Air Edge for Wider Bandwidth
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Solution Overview
Problem
Bulk acoustic wave resonators (BAWRs) face limitations in bandwidth and Q-factor due to losses from horizontal acoustic waves, which affect the Acousto-electric coupling coefficient and resonance characteristics.
Innovation Solution
The introduction of an air edge formed by etching a predetermined portion of the BAWR's edge, creating a steep slope and air gap structure to reflect horizontal acoustic waves, thereby reducing losses and enhancing the Acousto-electric coupling coefficient and bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the BAWR operates with conventional electrode and piezoelectric layer configurations, then the device structure is simple, but the Acousto-electric coupling coefficient is limited and bandwidth is narrow
Solution Approach 1:
The patent segments the edge of the BAWR into multiple regions by forming air edges at specific distances from the center. This segmentation creates distinct functional zones: a first air edge region for reflecting horizontal acoustic waves and a second air edge region for additional acoustic wave management, thereby enhancing the Acousto-electric coupling coefficient and bandwidth without substantially increasing overall device complexity
Solution Approach 2:
The patent applies local quality by creating air edges with specific geometries at predetermined locations around the perimeter of the piezoelectric layer. The air edges are formed with controlled depths and distances from the center, providing localized acoustic wave reflection and management properties that enhance overall device performance while maintaining a relatively simple global structure
2Reliability
If the BAWR uses conventional edge configurations, then the manufacturing process is simple, but horizontal acoustic waves cause energy loss and reduce Q-factor
Solution Approach 1:
The patent extracts horizontal acoustic waves from the system by introducing air edges that reflect these waves back into the piezoelectric layer. The air edges are formed by removing material (etching) to create air gaps that act as acoustic mirrors, effectively taking out the harmful horizontal wave propagation and converting it into useful vertical resonance, thereby improving Q-factor
Solution Approach 2:
The patent converts the harmful effect of horizontal acoustic waves into a beneficial effect by using air edges to reflect these waves. The horizontal waves that would normally cause energy loss are now reflected back to contribute to the vertical resonance mode, improving the Acousto-electric coupling coefficient and Q-factor while the manufacturing process remains relatively straightforward
3Adaptability or versatility
If air edges are formed by etching to create steep slopes, then the Acousto-electric coupling coefficient increases, but the manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the geometric parameters of the air edges, specifically the distance from the center and the depth of etching, to achieve steep slopes that effectively reflect horizontal acoustic waves. By carefully selecting these parameters (e.g., air edge distance of 5-15 micrometers from the center), the patent achieves high Acousto-electric coupling coefficients while maintaining manufacturability with standard semiconductor fabrication processes
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 configuration improves the Q-factor and bandwidth of BAWR, enabling its use in RF filters and duplexers with reduced band gaps, suitable for wireless communication devices, and reduces phase noise in oscillator applications.
Implementation Method 1
A bulk acoustic wave resonator (BAWR) operates by the application of an electric potential to electrodes that are disposed on and/or below a piezoelectric layer. The piezoelectric layer oscillates in response to a high frequency electric potential applied to the electrodes.
Implementation Method 2
an air edge formed at a predetermined distance from a center of the bulk acoustic wave resonance unit... creating a steep slope and air gap structure to reflect horizontal acoustic waves
Data Source
AI summary
Disclosed is a bulk acoustic wave resonator (BAWR). The BAWR includes a bulk acoustic wave resonance unit with a first electrode, a second electrode, and a piezoelectric layer. The piezoelectric layer is disposed between the first electrode and the second electrode. An air edge is formed at a distance from a center of the bulk acoustic wave resonance unit.