Defect and stress characterization of AlN films by Raman spectroscopy

Abstract

Raman spectroscopy was used to characterize the residual stress and defect density of AlN thin films reactively sputtered on silicon (100). The authors studied the correlation between the shift of the E2 (high) phonon of AlN at 658 cm-1 and the film biaxial stress and obtained a biaxial piezospectroscopic coefficient of 3.7 GPa cm-1. A correlation was found between the width of the Raman line, the oxygen concentration measured by secondary ion mass spectroscopy, and acoustic losses. This work lays the basis for the nondestructive assessment of two key thin film properties in microelectromechanical systems applications, namely, acoustic attenuation and residual stress

Structural and optical properties of thick freestanding AlN films prepared by hydride vapor phase epitaxy

“…4), suggesting that larger incorporation of oxygen is achieved at the interface of the film with the intermediate layer and the sapphire substrate. Larger incorporation of oxygen has been observed on the interface of GaN deposited on sapphire substrates, and more recently in heteroepitaxial AlN films [25]. A detailed SIMS impurity trace analysis is planned to measure the concentration of oxygen incorporated in films grown by the present growth method.…”

Encapsulated Aluminum Nitride SAW devices for liquid sensing applications

“…For further investigation, we used Raman spectroscopy measurements to evaluate the quality of the AlN layers deposited at 10W bias power. The crystallinity of AlN films which is related to interfaces, grain size and point defects, can be detected by the FWHM of the rocking curve of the E 2 (high) mode in Raman spectra [12]. The very high quality of an AlN bulk crystal with values of 3cm -1 was indicated by Kuball et al [13], while a value of 50cm −1 was reported by Perlin et al [14] for fully imperfect AlN crystals.…”

“…figure 3, the E 2 (high) mode of Raman spectroscopy measured from our AlN films is reported. The very high intensity and narrow rocking curve (with FWHM of 12.6 cm -1 ) indicate the good crystallinity of these layers [12]. Figure 4 depicts the process flow to fabricate encapsulated SAW devices.…”

Effect of carbon doping on microstructure, electronic and magnetic properties of Cr:AlN films

“…This further demonstrated that the Cr atoms located in the AlN crystal lattice. Additionally, the stress and deficiency of N or Cr could move the Raman shifts [23][24][25]. Chen et al have demonstrated that a tensile stress would induce Raman spectra blue-shifted for c-axis texture films [23].…”