Growth Of Aluminum Nitride Thin Films Research Articles

Structural Analysis of Mo Thin Films on Sapphire Substrates for Epitaxial Growth of AlN.

Aluminum nitride (AlN) thin film/molybdenum (Mo) electrode structures are typically required in microelectromechanical system applications. However, the growth of highly crystalline and c-axis-oriented AlN thin films on Mo electrodes remains challenging. In this study, we demonstrate the epitaxial growth of AlN thin films on Mo electrode/sapphire (0001) substrates and examine the structural characteristics of Mo thin films to determine the reason contributing to the epitaxial growth of AlN thin films on Mo thin films formed on sapphire. Two differently oriented crystals are obtained from Mo thin films grown on sapphire substrates: (110)- and (111)-oriented crystals. The dominant (111)-oriented crystals are single-domain, and the recessive (110)-oriented crystals comprise three in-plane domains rotated by 120° with respect to each other. The highly ordered Mo thin films formed on sapphire substrates serve as templates for the epitaxial growth by transferring the crystallographic information of the sapphire substrates to the AlN thin films. Consequently, the out-of-plane and in-plane orientation relationships among the AlN thin films, Mo thin films, and sapphire substrates are successfully defined.

Crystalline growth of AlN thin films by atomic layer deposition

Aluminum nitride (AlN) thin film was grown by plasma enhanced atomic layer deposition using trimethylaluminum and ammonia precursors. A method was found to have crystalline thin film AlN with almost zero thickness variation and a truly one layer deposition of atoms per each cycle of the process. The growth rate saturated at ∼ 1 Å/cycle, and the thickness was proportional to the number of reaction cycles. The preferred crystal orientation, uniformity of the nucleation and the surface roughness of the grown AlN were investigated. X-ray diffraction (XRD), atomic focused microscopy (AFM) and scanning electron microscopy (SEM) were carried out to analyze the crystallinity and properties of the films.

Elastic constants of aluminum nitride

AbstractWe report on the application of Brillouin spectroscopy as an approach to non‐destructive optical characterization of the elastic constants of semiconductors with the wurtzite symmetry. Three different configurations were used to achieve a complete determination of the elastic stiffness constants of bulk AlN substrates grown by the Physical Vapor Transport (PVT) method. The scattering diagrams of these three configurations are presented showing the geometrical arrangements necessary to observe all the elastic stiffness constants for the partially nontransparent wurtzite type of the crystal structure. Because aluminum nitride (AlN) is a suitable material for the fabrication of light emitting devices, the characterization of its elastic constants was carried out very precisely to provide a reliable data which can be used for the determination of residual stress arising during the growth of AlN thin films or wide band gap semiconductor thin films on substrates of AlN. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Elemental steps in the growth of AlN thin films on NiAl upon thermal decomposition of ammonia

Ammonia adsorption at T=80 K on NiAl(111) and NiAl(001) and subsequent thermal decomposition at elevated temperatures leads to the formation of aluminum nitride (AlN). After annealing to T=600 K, NH3 is dissociated completely and atomic nitrogen is adsorbed on the surface. At temperatures between 800 and 1200 K, an intermediate AlN state is found. The formation process of AlN has finished after annealing to 1200 K. Well-ordered AlN thin films on NiAl(001) and NiAl(111) can be prepared by several cycles of ammonia adsorption at T=80 K and annealing to 1250 K. The films render a distinct low-energy electron diffraction pattern with hexagonal (AlN/NiAl(111)) or pseudo-twelvefold (AlN/NiAl(001)) symmetry. High resolution electron energy loss spectra of ordered AlN films show a Fuchs–Kliewer phonon mode at 865 cm−1 in good agreement with theoretical spectra on the base of the dielectric theory. The electronic gap of the thin AlN films is determined to be Eg≂6.1 eV. Gap states at 1.1 and 5.1 eV were found for AlN/NiAl(111) as well as for AlN/NiAl(001).

Real time stress measurements and elastic constant of aluminum nitride thin films on Si(111)

This article addresses stress effects in sputter deposited aluminum nitride (AlN) thin films on Si(111). One of the elastic constants of AlN (C33) was measured directly. Real time stress measurements during growth of AlN thin films yield corroborating results for polycrystalline film growth and new results which indicate large intrinsic stresses during epitaxial growth of AlN on Si(111).