STUDY OF THE LATTICE STRUCTURE AND SOUND VELOCITY IN ALN FILMS ON A SILICON SUBSTRATE FOR THE DEVELOPMENT OF ACOUSTIC RESONATORS
A. L. Bogoslovtseva1, O. N. Shevchenko1,2, N. A. Nikolaev1,2, A. A. Rybak1,2, D. S. Gribanov1,2, S. V. Adishchev2, E. A. Dobrynina2, S. Yu. Chepkasov1, P. V. Geydt1
1Novosibirsk State University, Novosibirsk, Russia
2Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: Pulsed terahertz spectroscopy, infrared spectroscopy, speed of sound, AlN, Raman scattering
Abstract
This work is devoted to the study of acoustic phonon scattering in aluminum nitride (AlN) thin films grown by magnetron sputtering with an emphasis on their potential application as piezoactive layers for microwave resonators. The main objective of the work is to establish a correlation between the data obtained by various analytical methods, including Mandelstam-Brillouin scattering (MBS), Raman scattering (RS), infrared (IR) and terahertz (THz) spectroscopy, as well as X-ray diffraction (XRD), to assess the quality and homogeneity of AlN films. The data analysis confirmed the high stability of the MBS peaks in the studied films. It was found that the stability of the MBS phonon peak reaches 87.6 ± 0.5 GHz, which corresponds to the literature data, and confirms the homogeneity of the films with an error of less than 1 %. The presence of a specific peak in the XRD patterns and the minimum width of the phonon peak obtained by Raman and FTIR spectroscopy confirm the possibility of using these methods to characterize such micron-thick films. Considering that the peak frequency of the phonon resonance did not change for films with a thickness of 4.5 μm, it is assumed that the analysis of the phonon line width may be sufficient to evaluate the grown films. The Raman method seems to be especially promising, which in the future can allow in situ analysis during the growth of AlN films. Thin AlN films with a thickness of less than 7 μm have the quality sufficient for the development of acoustic microwave resonators, which opens the way for the experimental creation of multilayer structures with different acoustic impedances based on the obtained data.
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