AVS 47th International Symposium
    Thin Films Tuesday Sessions
       Session TF-TuA

Paper TF-TuA6
Structural Studies of AlN Thin Films during Low Temperature RF Sputter Deposition

Tuesday, October 3, 2000, 3:40 pm, Room 203

Session: Mechanical Properties of Thin Films
Presenter: F. Engelmark, University of Uppsala, Sweden
Authors: F. Engelmark, University of Uppsala, Sweden
G.F. Iriarte, University of Uppsala, Sweden
I.V. Katardjiev, University of Uppsala, Sweden
M. Ottosson, University of Uppsala, Sweden
P. Muralt, Laboratiore de Ceramique, Switzerland
S. Berg, University of Uppsala, Sweden
Correspondent: Click to Email
AlN is a material used in a wide variety of applications such as electro-acoustic devices, blue diodes, IR-windows, thermal conductors, MIS-structures, IC-packaging, etc. Thin piezoelectric AlN polycrystalline films have been grown on Si and SiO@sub 2@ using RF magnetron sputter deposition in an Ar/N@sub 2@ gas mixture. The structural properties of the films have been optimized by varying the deposition parameters, such as process pressure, gas mixture, substrate temperature, discharge power, etc. It was found that the best film texture was obtained for a particular set of parameters, namely process pressure of 8 mTorr, substrate temperature 350°C, discharge power 350W and a gas mixture of 25%Ar and 75%N@sub 2@. The films as examined by XRD exhibited a columnar structure with a strong (002) texture, and a FWHM rocking curve of 1.6 degrees. A crystallite size of 38 nm was calculated using Sherrers formula. AFM measurements indicated a surface roughness with an rms value of 8 Å. Classical nonapodized transversal SAW filters operating at a frequency of 534 MHz were fabricated to estimate the electro-acoustic properties of the films. The measurements indicated a coupling coefficient of 0.46% and a phase velocity of 4900 m/s. Further, thin epitaxial films were grown on alfa-Al@sub 2@O@sub 3@(001) under the same deposition conditions. The films exhibited a (001)AlN//(001)alfa-Al@sub 2@O@sub 3@ plane orientation with a (002) rocking curve FWHM value of about 0.4 degrees, indicating a relatively good alignment of the c-axis or a low dislocation density. The in-plane orientation was [110]AlN//[120]alfa-Al@sub 2@O@sub 3@ corresponding to a rotation of the AlN film of 30 degrees with respect to the alfa-Al@sub 2@O@sub 3@(001) surface. Cross-sectional TEM studies indicated a population of both thread and edge dislocations with decreasing concentrations with film thickness.