Ku-Band Alscn-on-Diamond SAW Resonators with Phase Velocity Above 8600 M/S
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-06-29 |
| Authors | Tzu-Hsuan Hsu, Kapil Saha, Jack J. Kramer, Omar Barrera, Paolo Simoni |
| Institutions | Northeastern University, The University of Texas at Austin |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: AlScN-on-Diamond SAW Resonators
Section titled âTechnical Documentation & Analysis: AlScN-on-Diamond SAW ResonatorsâThis document analyzes the research demonstrating high-performance Ku-band Surface Acoustic Wave (SAW) resonators utilizing an Aluminum Scandium Nitride (AlScN) thin film on a Polycrystalline CVD Diamond (PCD) substrate. The findings validate diamondâs role as the premier substrate for next-generation, high-frequency, high-power acoustic devices.
Executive Summary
Section titled âExecutive Summaryâ- Record Phase Velocity: The AlScN-on-Diamond platform achieved an exceptional Sezawa mode phase velocity (vp) of 8671 m/s at 12.9 GHz, exceeding high-velocity alternatives like SiC and Sapphire by over 20%.
- High Q and Coupling: The prototype demonstrated a high maximum Quality Factor (Qmax) of 408 and an electromechanical coupling coefficient (k2eff) of 2.1%.
- Ku-Band Scalability: The platform successfully spanned the entire Ku-band (12-18 GHz) and demonstrated frequency tunability through variations in the normalized thickness ratio (h/λ).
- Superior Thermal Management: Leveraging diamondâs thermal conductivity (>1500 W/(m·K)), the device validated robust power handling capabilities above 12.5 dBm, crucial for thermally demanding 6G FR3 applications.
- Material Advantage: The use of MPCVD Polycrystalline Diamond (PCD) provides a cost-effective, high-acoustic-velocity substrate solution that ensures proper acoustic confinement without requiring heavy electrode loading.
- 6CCVD Relevance: This research directly validates the need for high-quality, polished MPCVD PCD substrates, a core offering of 6CCVD, for advanced acoustic and RF filtering applications.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes the key performance metrics and material properties achieved using the AlScN-on-Diamond platform.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Phase Velocity (vp) | 8671 | m/s | Sezawa Mode, 12.9 GHz |
| Maximum Quality Factor (Qmax) | 408 | - | Sezawa Mode |
| Electromechanical Coupling (k2eff) | 2.1 | % | Sezawa Mode |
| Operating Frequency (fs) | 12.9 | GHz | Ku-band (FR3) |
| Power Handling | > 12.5 | dBm | Experimentally validated |
| Diamond Substrate Thickness | 300 | ”m | Polycrystalline CVD Diamond |
| AlScN Film Thickness | 200 | nm | Al0.7Sc0.3N |
| Electrode Thickness | 50 | nm | Aluminum (Al) |
| Diamond Thermal Conductivity | > 1500 | W/(m·K) | Critical for thermal management |
| Substrate Surface Roughness (Ra) | < 20 | nm | Required for AlScN deposition |
| Diamond Longitudinal Velocity (vL) | 17521 | m/s | Comparison baseline (Fig 1c) |
Key Methodologies
Section titled âKey MethodologiesâThe fabrication and characterization of the AlScN-on-Diamond SAW resonators followed these critical steps:
- Substrate Selection: A 300 ”m thick Polycrystalline CVD Diamond (PCD) substrate was selected for its high acoustic velocity and thermal conductivity.
- Surface Preparation: The PCD substrate was polished to a surface roughness (Ra) of less than 20 nm to ensure high-quality deposition of the piezoelectric film.
- Piezoelectric Film Deposition: A 200 nm thick Al0.7Sc0.3N thin film was deposited via sputtering.
- Crystallinity Verification: X-Ray Diffraction (XRD) rocking curve measurement confirmed the wurtzite crystal structure quality, yielding a RC angle of 3.42°.
- Interdigital Transducer (IDT) Fabrication: 50 nm thick Aluminum (Al) electrodes were deposited and patterned. The prototype used 160 electrode pairs (Ne) and 120 pairs of reflective gratings.
- RF Characterization: Frequency response and admittance spectra were measured using a Keysight VNA and GSG prober under standard SOLT calibration to extract Qmax and k2eff.
- Power Handling Test: The device was repeatedly tested with incident power (Pin) ranging from -7.5 dBm up to 12.5 dBm to validate thermal robustness.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the high-specification diamond materials required to replicate, scale, and advance this critical Ku-band SAW resonator technology. Our MPCVD diamond substrates provide the necessary acoustic performance, thermal stability, and surface quality for next-generation RF devices.
Applicable Materials
Section titled âApplicable Materialsâ| Research Requirement | 6CCVD Material Recommendation | Technical Justification |
|---|---|---|
| Polycrystalline CVD Diamond (PCD) Substrate (300 ”m thick) | Acoustic Grade PCD Wafers | Provides the high acoustic velocity (vL 17521 m/s) and exceptional thermal conductivity (>1500 W/(m·K)) essential for high-frequency, high-power SAW operation. |
| High Surface Quality (Ra < 20 nm) | Precision Polished PCD | 6CCVD guarantees surface roughness (Ra) < 5 nm on inch-size PCD wafers, significantly surpassing the paperâs requirement and ensuring optimal interface quality for AlScN growth and minimal acoustic scattering loss. |
| Future SCD Exploration (Mentioned in paper) | Optical Grade Single Crystal Diamond (SCD) | For researchers seeking the ultimate material purity and lowest acoustic loss, 6CCVD offers SCD substrates up to 500 ”m thick with Ra < 1 nm, ideal for exploring fundamental limits of acoustic performance. |
Customization Potential
Section titled âCustomization PotentialâThe success of the AlScN-on-Diamond platform relies heavily on precise material engineering, which is 6CCVDâs core expertise:
- Custom Dimensions and Thickness: The paper utilized a 300 ”m thick substrate. 6CCVD offers PCD plates up to 125 mm in diameter and custom thicknesses for both SCD and PCD ranging from 0.1 ”m up to 500 ”m, enabling precise control over acoustic mode confinement and frequency tuning (h/λ ratio).
- Integrated Metalization Services: While the paper used Al, 6CCVD offers in-house metalization capabilities (Au, Pt, Pd, Ti, W, Cu). This service allows engineers to integrate high-conductivity or adhesion layers directly onto the diamond substrate, streamlining the fabrication of complex IDT structures.
- Laser Cutting and Shaping: 6CCVD can provide custom laser cutting and shaping services to meet specific device geometries and aperture requirements, ensuring high yield and precision for large-scale fabrication efforts.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and engineers specializes in optimizing diamond properties for demanding applications. We offer consultation services to assist researchers in:
- Material Selection: Determining the optimal diamond grade (PCD vs. SCD) and doping level (BDD for conductive applications) based on specific acoustic or RF requirements.
- Surface Preparation Optimization: Tailoring polishing specifications to maximize the quality of subsequent thin-film depositions (e.g., AlScN, LiNbO3).
- Thermal Modeling Support: Providing accurate thermal properties data for diamond substrates to aid in the design of high-power handling Ku-band RF filters and other thermally demanding wireless systems.
Call to Action: For custom specifications or material consultation regarding high-frequency acoustic platforms, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available).
View Original Abstract
In this work, an Aluminum Scandium Nitride (AlScN) on Diamond Sezawa-mode surface acoustic wave (SAW) platform for RF filtering at Ku-band (12-18 GHz) is demonstrated. Thanks to the high acoustic velocity and low-loss diamond substrate, the prototype resonator at 12.9 GHz achieves a high phase velocity ($v_p$) of 8671 m/s, a maximum Bode-$Q$ of 408, and coupling coefficient ($k_{\mathrm{eff}}^2$) of 2.1%, outperforming high-velocity substrates such as SiC and sapphire by more than 20% in velocity. Resonators spanning 8-18 GHz are presented. The platformâs high power handling above 12.5 dBm is also experimentally validated.