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Homogeneity and Thermal Stability of Sputtered Al0.7Sc0.3N Thin Films
José Manuel Carmona-Cejas1, Teona Mirea1, Jesús Nieto1
1CEMDATIC-ETSI Telecomunicación, Universidad Politécnica de Madrid, Av. Complutense 30, 28040 Madrid, Spain.
Materials (Basel, Switzerland)
|March 29, 2023
Summary
This study investigated aluminum scandium nitride (AlScN) films, finding significant variations in piezoelectric activity across the wafer due to deposition conditions. Thermal stability was assessed, but improvements were limited.
Area of Science:
- Materials Science
- Thin Film Technology
- Piezoelectric Materials
Background:
- Aluminum Scandium Nitride (AlScN) is a promising piezoelectric material for advanced applications.
- Understanding film homogeneity and thermal stability is crucial for device performance.
Purpose of the Study:
- To evaluate the homogeneity and thermal stability of AlScN films sputtered from segmented targets.
- To correlate structural properties with piezoelectric activity and identify factors affecting performance.
Main Methods:
- Sputtering deposition of AlScN films on Si and acoustic mirror substrates.
- Post-deposition annealing up to 700 °C in vacuum.
- Characterization using Rutherford Backscattering Spectrometry (RBS), Nuclear Reaction Analysis (NRA), Atomic Force Microscopy (AFM), and X-ray Diffraction (XRD).
Main Results:
- AlScN films exhibited radial inhomogeneity in piezoelectric activity, with reduced performance in the central zone.
- Lower piezoelectric activity correlated with increased oxygen adsorption and poorer crystalline structure, possibly due to ion bombardment.
- Increased surface roughness and potential coexistence of a non-piezoelectric ScN phase were observed in the central area.
- Thermal treatments showed limited improvement in piezoelectric activity and crystalline structure.
Conclusions:
- Deposition process control is critical for achieving homogeneous piezoelectric properties in AlScN films.
- Ion bombardment during sputtering negatively impacts film quality and piezoelectric response.
- AlScN films show moderate thermal stability, but significant improvements in performance via annealing were not achieved.
