Synthesis and Surface Acoustic Wave Properties of AlN Thin Films Fabricated on (001) and (110) Sapphire Substrates Using Chemical Vapor Deposition of AlCl_3-NH_3 System

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Thin films of AlN were prepared on sapphire C- and A-plane by chemical vapor deposition. Crystal orientations, oxygen impurity contents and surface acoustic wave properties (SAW) of the films were investigated. Under optimized conditions, epitaxial AlN films were deposited and the crystal orientation relationships were (001)[110]AlN⫽(001)[11^^-0]Al_2O_3 and (001)[110]AlN⫽(110)[11^^-0]Al_2O_3. The crystal orientation of the AlN films decreased as the thickness of the films increased slightly, and the oxygen impurity content was less than 1 atm% for both systems. The dependences of SAW velocity (V_s) and the temperature coefficient of the center frequency (T_f) on the film thickness were measured, and T_f was found to increase as the film thickness increased for all measurment directions; however, zero-temperature coefficient was not achieved.
社団法人応用物理学会の論文
1997-05-15