| AVS 58th Annual International Symposium and Exhibition | |
| Thin Film Division | Tuesday Sessions |
| Session TF-TuA |
| Session: | ALD: Fundamental Reactions and Film Properties |
| Presenter: | Ya-Chuan Perng, University of California Los Angeles |
| Authors: | Y.-C. Perng, University of California Los Angeles J.P. Chang, University of California Los Angeles |
| Correspondent: | Click to Email |
Wide bandgap semiconductors, such as SiC and GaN, are known as base materials in electronic devices operating under high temperatures and high electric fields. Aluminum nitride (AlN) is a promising interfacial layer or dielectric material for SiC and GaN due to its material properties, such as wide bandgaps, similar atomic arrangement and small lattice mismatch (1.3% and 2.6%). Although various deposition methods, such as chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE), have been used, synthesizing high quality AlN thin films for those applications is still an issue, especially in the view of controllability in atomic scales. Atomic layer deposition (ALD) is used to synthesize AlN thin layer on SiC, GaN and Si to achieve atomic controllability and assess the possibility to extend this deposition method to nitride growth and how the substrate properties affect the interface quality and corresponding electrical properties of the synthesized film
The AlN thin films were synthesized at 400~600oC via a chamber with the base pressure as 10-7 torr, using trimethylaluminum (TMA) and blue grade ammonia (NH3) as precursors. The surface structure during the deposition was monitored via in-situ RHEED and the growth rate was 0.5~2Å/cycle as a function of the deposition temperature. The surface composition, including the impurities, was found to be correlated to the deposition temperature, verified by in-situ x-ray photoelectron spectroscopy (XPS). The surface morphology of the films was studied by transmission electron microscopy (TEM) and atomic force microscope (AFM) and found to be conformal because the rms value was found to be less than 10Å on SiC, which is the same as that of the substrate surface roughness. The capacitance/conductance-voltage characteristics were measured to determine the dielectric constant of the ALD film and interpret the interface states density, which were 8 and on the order of 1012 cm-2eV-1, respectively, comparable to that reported for MBE synthesized AlN.