XBAR Electrode Sidewall Angles for Wideband 5G RF Filters
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Solution Overview
Problem
Existing RF filters using acoustic wave resonators are not well-suited for higher frequencies and bandwidths required in future communications networks, particularly in 5G NR standards which include bands n77 and n79 operating at frequencies between 3.3 GHz and 5 GHz.
Innovation Solution
The development of a Transversely-Excited Film Bulk Acoustic Resonator (XBAR) with controlled conductor side-wall angles, specifically trapezoidal cross-sectional shapes with sidewall angles between 70 degrees and 110 degrees, to enhance the frequency capability and electromechanical coupling of RF filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional acoustic wave resonators are used, then existing RF filter designs can be maintained, but frequency capability and bandwidth are insufficient for future communications networks
Solution Approach 1:
The patent changes the geometric parameters of the conductor electrodes by introducing specific sidewall angles (70-110 degrees) and trapezoidal cross-sectional shapes. This parameter modification optimizes the electromechanical coupling and enables the resonator to achieve high frequency capability (3.3-5 GHz and beyond) while maintaining reliable performance, resolving the contradiction between frequency capability and performance reliability at higher frequencies.
2Speed
If electrode geometry is optimized for higher frequencies, then frequency capability improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a range of acceptable sidewall angles (70-110 degrees) rather than a single precise value. This parameter range approach allows manufacturing processes to achieve the desired frequency capability while accommodating normal manufacturing tolerances, thus resolving the contradiction between frequency capability improvement and manufacturing precision requirements.
3Power
If trapezoidal conductor shapes are implemented, then electromechanical coupling is enhanced, but device complexity increases
Solution Approach 1:
The patent modifies the conductor electrode geometry to have trapezoidal cross-sections with specific sidewall angles. This controlled geometric change enhances the electromechanical coupling coefficient by optimizing the electric field distribution and interaction with the acoustic wave, while the relatively simple modification (adding sidewall angle control to standard electrode deposition) keeps the overall device complexity manageable.
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 XBAR resonators provide high electromechanical coupling and frequency capability, enabling the design of RF filters that can effectively handle the higher frequencies and wider bandwidths required for future communications networks, while also controlling spurious modes and improving manufacturing tolerances.
Implementation Method 1
a piezoelectric plate having opposing first and second surfaces; and a first electrode and a second electrode disposed on the first surface of the piezoelectric plate, the first and second electrodes and the piezoelectric plate configured such that a radio frequency signal applied between the first and second electrodes excites a shear primary acoustic mode in the piezoelectric plate
Data Source
AI summary
Acoustic resonator devices and methods are disclosed. An acoustic resonator device includes a piezoelectric plate having opposed front and back surfaces. A first electrode and a second electrode are formed on the front surface of the piezoelectric plate, the first and second electrodes and the piezoelectric plate configured such that a radio frequency signal applied between the first and second electrodes excites a shear primary acoustic mode in the piezoelectric plate. The first electrode and the second electrode have trapezoidal cross-sectional shapes. A sidewall angle of at least one side surface of the first electrode and a sidewall angle of at least one side surface of the second electrode are greater than or equal to 70 degrees and less than or equal to 110 degrees.