DocumentCode :
2520922
Title :
Growth of piezoelectric aluminium nitride for layered SAW devices
Author :
Assouar, M.B. ; Elmazria, O. ; Brizoual, L. Le ; Belmahi, M. ; Alnot, P.
Author_Institution :
Lab. de Phys. des Milieux Ionises et Applications, CNRS, Vandoeuvre, France
fYear :
2002
fDate :
2002
Firstpage :
333
Lastpage :
336
Abstract :
A piezoelectric film combined with a high velocity substrate such as diamond seems very promising for SAW devices operating at high frequencies. In this work, we investigate the optimisation of growth parameters to produce AlN films with required properties for SAW devices: high resistivity, low roughness and good piezoelectricity coupling. AlN films are deposited by reactive DC magnetron sputtering on [100] silicon substrates under various deposition conditions including N2 concentration in Ar-N2 gas mixture, sputtering pressure (3×10-3 to 9×10-3 mbar), DC power (100-400 W) and substrate temperature (100 to 600°C). The growth duration was modulated to obtain a constant film thickness (2 μm) to permit better comparison. X-ray diffraction shows that the AlN films deposited in the range of 60-80% N2, 400°C, and 6×10-3 mbar, exhibit columnar structure textured in [002] orientation corresponding to wurtzite structure with the c-axis oriented perpendicular to the surface. AlN films elaborated in optimum conditions exhibit low surface roughness (<5 nm) and high electrical resistivity (>1014 Ω.cm). The stoichiometric composition determined by energy dispersive X-ray spectroscopy (EDXS) reveals a weak presence of oxygen in the Al1N1 films. The best compromise is obtained for the sample grown with 75% N2. A SAW filter is formed by development of IDT of 32 μm wavelength on AlN/Si and AlN/sapphire structures. For AlN film grown with 75% N2, frequency responses measured by network analyser show a central frequency of 156.4 MHz and 176 MHz corresponding to phase velocities of 5004.8 and 5632 m/s respectively for silicon and sapphire substrates. Also, we have formed a layered structure AlN/diamond SAW device which does not exhibit an operating frequency due to high surface roughness of the diamond film.
Keywords :
X-ray chemical analysis; aluminium compounds; electrical resistivity; interface structure; optimisation; piezoelectric thin films; sputter deposition; stoichiometry; surface acoustic wave filters; surface topography; 100 to 400 W; 100 to 600 C; 156.4 MHz; 176 MHz; 2 micron; 3 to 9 mubar; 32 micron; 400 C; 5004.8 m/s; 5632 m/s; 6 mubar; Al2O3; AlN films; AlN-Al2O3; AlN-C; AlN-Si; AlN/Si structures; AlN/sapphire structures; Ar-N2; Ar-N2 gas mixture; C; DC power; EDT wavelength; EDXS; N2 concentration; SAW filter; Si; X-ray diffraction; central frequency; columnar structure; constant film thickness; deposition conditions; diamond film surface roughness; energy dispersive X-ray spectroscopy; frequency responses; growth duration; growth parameters optimisation; high velocity diamond substrate; layered SAW devices; layered structure AlN/diamond SAW device; operating frequencies; perpendicular c-axis orientation; phase velocity; piezoelectric aluminium nitride growth; piezoelectric film; piezoelectricity coupling; reactive DC magnetron sputtering; resistivity; silicon [100] substrate; sputtering pressure; stoichiometric composition; substrate temperature; surface acoustic wave devices; surface roughness; weak oxygen presence; wurtzite structure; Aluminum; Frequency; Piezoelectric devices; Piezoelectric films; Rough surfaces; Semiconductor films; Sputtering; Substrates; Surface acoustic wave devices; Surface roughness;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Frequency Control Symposium and PDA Exhibition, 2002. IEEE International
Print_ISBN :
0-7803-7082-1
Type :
conf
DOI :
10.1109/FREQ.2002.1075903
Filename :
1075903
Link To Document :
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