XBAR Resonator Structure With Lower Thermal Impedance
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Solution Overview
Problem
Current RF filters using acoustic wave resonators are not well-suited for higher frequencies and bandwidths required in future communication networks, particularly in 5G NR standards, due to limitations in thermal impedance, which affects their performance and efficiency.
Innovation Solution
The development of Transversely-Excited Film Bulk Acoustic Resonators (XBARs) with improved thermal impedance by removing predetermined areas of the bonding oxide layer and piezoelectric layer from selected locations, allowing for efficient heat conduction from the IDT or busbars to the substrate, thereby reducing thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional acoustic wave resonators are used in RF filters, then the filters can operate at standard frequencies, but the thermal impedance is too high for higher frequencies and bandwidths required in future communication networks
Solution Approach 1:
The patent segments the bonding oxide layer and piezoelectric layer into removed portions and retained portions. By removing specific areas of these layers from selected locations, the patent creates thermal pathways that reduce thermal impedance while preserving the structural integrity and electrical functionality of the resonator for high-frequency operation
Solution Approach 2:
The patent applies local quality by creating non-uniform layer structures - removing bonding oxide and piezoelectric layers from selected locations where thermal management is critical, while retaining these layers in other areas where electrical isolation and piezoelectric functionality are needed. This localized modification reduces thermal impedance specifically in heat-growth regions without compromising overall device performance
2Temperature
If the bonding oxide layer and piezoelectric layer are removed from selected locations, then thermal resistance is reduced by 10% to 30%, but the structural complexity of the device increases
Solution Approach 1:
The patent extracts (removes) the bonding oxide layer and piezoelectric layer from selected locations to create thermal pathways. This extraction reduces thermal resistance by 10% to 30% while maintaining the essential structure of the device. The removed portions are strategically located to maximize thermal management benefits without requiring complete structural redesign
Solution Approach 2:
The patent introduces dynamic thermal management capabilities by creating variable thickness regions in the bonding oxide and piezoelectric layers. These dynamic structural variations allow the device to adapt thermal pathways based on operational heat generation, reducing thermal resistance where needed while maintaining structural integrity elsewhere
3Temperature
If the bonding oxide layer and piezoelectric layer are removed to improve heat conduction, then thermal management is enhanced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by performing the layer removal process during the fabrication sequence at a stage where subsequent processing steps can accommodate the modified structure. The bonding oxide and piezoelectric layers are removed from selected locations before final device assembly, allowing for thermal pathway optimization without compromising manufacturing feasibility or requiring post-assembly modifications
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 solution enhances the thermal management of XBARs, leading to extended operating life and higher output power in high-frequency channels, with a potential reduction in thermal resistance by 10% to 30%, thereby improving the performance of RF filters in next-generation communication systems.
Implementation Method 1
removing predetermined areas of the bonding oxide layer and piezoelectric layer from selected locations, allowing for efficient heat conduction from the IDT or busbars to the substrate
Data Source
AI summary
An acoustic resonator device with low thermal impedance has a substrate and a single-crystal piezoelectric plate having a back surface attached to a top surface of the substrate via a bonding oxide (BOX) layer. An interdigital transducer (IDT) formed on the front surface of the plate has interleaved fingers disposed on the diaphragm. The piezoelectric plate and the BOX layer are removed from a least a portion of the surface area of the device to provide lower thermal resistance between the conductor pattern and the substrate.