Aluminum Nitride Micro-Channels Grown via Metal Organic Vapor Phase Epitaxy for MEMs Applications
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1040-Q09-28
Aluminum Nitride Micro-Channels Grown via Metal Organic Vapor Phase Epitaxy for MEMs Applications L. E. Rodak, Sridhar Kuchibhatla, P. Famouri, Ting Liu, and D. Korakakis Lane Department of Computer Science and Electrical Engineering, West Virginia University, PO Box 6109, Morgantown, WV, 26506 ABSTRACT Aluminum nitride (AlN) is a promising material for a number of applications due to its temperature and chemical stability. Furthermore, AlN maintains its piezoelectric properties at higher temperatures than more commonly used materials, such as Lead Zirconate Titanate (PZT) [1, 2], making AlN attractive for high temperature micro and nano-electromechanical (MEMs and NEMs) applications including, but not limited to, high temperature sensors and actuators, micro- channels for fuel cell applications, and micromechanical resonators. This work presents a novel AlN micro-channel fabrication technique using Metal Organic Vapor Phase Epitaxy (MOVPE). AlN easily nucleates on dielectric surfaces due to the large sticking coefficient and short diffusion length of the aluminum species resulting in a high quality polycrystalline growth on typical mask materials, such as silicon dioxide and silicon nitride [3,4]. The fabrication process introduced involves partially masking a substrate with a silicon dioxide striped pattern and then growing AlN via MOVPE simultaneously on the dielectric mask and exposed substrate. A buffered oxide etch is then used to remove the underlying silicon dioxide and leave a free standing AlN micro-channel. The width of the channel has been varied from 5 µm to 110 µm and the height of the air gap from 130 nm to 800 nm indicating the stability of the structure. Furthermore, this versatile process has been performed on (111) silicon, c-plane sapphire, and gallium nitride epilayers on sapphire substrates. Reflection High Energy Electron Diffraction (RHEED), Atomic Force Microscopy (AFM), and Raman measurements have been taken on channels grown on each substrate and indicate that the substrate is influencing the growth of the AlN micro-channels on the SiO2 sacrificial layer. INTRODUCTION Aluminum Nitride (AlN) possesses several properties, including but not limited to, a wide band gap (6.2 eV), high thermal conductivity, high mechanical strength, and good resistance to corrosion, which make the material attractive for use in a number of applications, especially at high temperatures and in harsh environments [5]. Other characteristics, including its piezoelectric and acoustic properties, result in AlN being used in surface acoustic wave (SAW) and bulk acoustic wave (BAW) devices [6]. In particular, AlN is a material of interest for high temperature micro-electromechanical (MEMS) devices, such as resonators and RF switches [6], due to the fact that it exhibits the highest piezoelectric coefficient of the III-Nitrides and is anticipated to maintain these properties at temperatures up to 1200 °C [7]. Furthermore, AlN is more compatible with conventional silicon MEMs technology that other piezoelectri
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