Fourier Transform Infrared Spectroscopy Characterization of AlN Thin Films Grown on Sacrificial Silicon Oxide Layers via
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1222-DD02-28
Fourier Transform Infrared Spectroscopy Characterization of AlN Thin Films Grown on Sacrificial Silicon Oxide Layers via Metal Organic Vapor Phase Expitaxy Sridhar Kuchibhatla1,L.E. Rodak1,D. Korakakis1,2 1 Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown ,WV 26506 2 National Energy Technology Laboratory, Morgantown, WV 26507-0880
ABSTRACT:
Aluminum Nitride (AlN) films were grown using Metal Organic Vapor Phase Epitaxy (MOVPE) techniques on Si (111) substrates patterned with SiOx stripes and the vibrational properties of these films were investigated by Fourier transform infrared (FTIR) techniques. The grown films contained a predominantly wurtzite AlN phase in addition to oxidized aluminum and mixed AlN phases. The AlN film on amorphous silicon oxide (SiOx) was prone to corrosion when subjected to wet etching in buffered hydrofluoric acid solution thereby changing the material properties of the AlN film on SiOx. The etching process significantly reduced the oxidized aluminum phase and mixed AlN phases.
INTRODUCTION:
Wide bandgap group III Nitride materials such as Aluminum Nitride (AlN) and its alloys have attracted considerable attention for the fabrication of Micro/Nano electromechanical systems (MEMS/NEMS) devices due to their excellent bio compatibility, well developed growth techniques for high quality thin films and chemical stability at high temperatures in comparison to other common piezoelectric materials such as quartz, polyvinylidelflouride (PVDF) and metal oxides [1]. Among the group III nitrides wurtzite AlN exhibits excellent piezoelectric properties and is expected to maintain its properties up to 1150°C [2]. Even though the piezoelectric properties depend on the microstructure of the films, polycrystalline AlN films with preferred caxis orientation are known to exhibit properties similar to crystalline AlN films. Typically reactive sputtering techniques have been used to deposit polycrystalline AlN films on a variety of sacrificial layers such as amorphous silicon oxide (SiOx) to fabricate free standing bridges [3]. However, the sputtered AlN system requires an underlying mechanical support structure such as silicon nitride (Si3N4) due to the low mechanical strength of the sputtered AlN films [4]. In the Metal Organic Vapor Phase Epitaxy (MOVPE) of certain III Nitride materials, dielectric layers, such as SiOx or Si3N4, can be used as a mask to promote selective growth as seen in the Selective Area Growth (SAG) or Epitaxial Lateral Overgrowth (ELOG) of GaN. However, the high sticking coefficient and short diffusion length of Al species during MOVPE growth results in the nucleation of Al containing alloys on dielectric layers [5]. Specifically, the growth of AlxGa1-xN (0
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