DETERMINATION OF PHYSICAL RESPONSE IN (Mo/AlN) SAW DEVICES

Abstract

This paper describes the experimental conditions in surface acoustic wave (SAW) designed on aluminum nitride (AlN) films grown on Si3N4 substrates by using pulsed laser deposition. Moreover it was studied the dependency of optical properties with temperature of deposition. The thickness, measured by profilometry technology, was 150 nm for all films. Moreover, SAW devices with a Mo/AlN/Si3N4 configuration were fabricated employing AlN buffer and Mo Channel. The morphology and composition of the films were studied using atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy analysis (XPS), respectively. The optical reflectance spectra and color coordinates of the films were obtained by optical spectral reflectometry technique in the range of 400–900 cm-1. In this work, a clear dependence in morphological properties, optical properties, frequency response and acoustic wave velocity as function of applied deposition temperature was found. It was also observed a reduction in reflectance of about 10% and an increase of acoustic wave velocity of about 1.2% when the temperature was increased from 200°C to 630°C.

Correlation Between Optical, Morphological, and Compositional Properties of Aluminum Nitride Thin Films by Pulsed Laser Deposition

“…In previous works, we have shown the influence of the surface quality of the AlN nanostructures as substrates for Surface Acoustic Wave sensor (SAW) [16], its composition and surface roughness have a critical impact on the quality of the device. As the surface acoustic wave is only propagated on the surface, all the energy is concentrated almost within a wavelength from the surface to the inside.…”

Research Perspectives on Functional Micro- and Nanoscale Coatings

“…The peaks at 534.4 eV, 397.3 eV, 124.4 eV, and 73.9 eV correspond to O1s, N1s, Al2s, and Al2p binding energies, respectively. Calculation of the peak areas of deconvoluted spectrum (Figure 7) without O1s contribution gives an atomic ratio of Al:N = 0.392: 0.588, which is similar to the stoichiometry of Al 0.40 N 0.60 (Caicedo et al, 2013). The core electronic spectra carry the information about the chemical composition and bonding character of the Al-N films.…”

“…The IR-spectra provided important information about the composition, homogeneity, crystallinity and the residual stresses present in the films. Moreover, the ellipsometry and reflectance measurements have been used to determine the refractive index in many AlN compounds, since the ellipsometry and reflectance are sensitive and non-destructive techniques used for Levinshtein et al, 2001;Morkoc, 2013;Ruterana et al, 2006 studies of optical properties and microstructures of surfaces and thin films (Caicedo, Pérez, Caicedo, & Riascos, 2013;Pérez, Riascos, Caicedo, Cabrera, & Yate, 2011a;Rosenberger, Baird, McCullen, Auner, & Shreve, 2008;Zhuang et al, 2009). Additionally, single-chip front-end RF modules incorporating Surface Acoustic Wave (SAW) filters are a matter of intense research.…”

“…The variation of grain size and roughness (Figure 10) obtained in the Al-N films suggest that thermal activation generated by the increasing in the deposition temperature on surface substrates modifies the superficial morphology by increasing the energy associated with atoms on the substrate surface and/or the growing film surface which produces a relative reduction of grain size and roughness. (Caicedo et al, 2013)…”

“…confirm that frequency response characteristics (insertion loss) can be affect by reduction of oxygen concentration, reduction of grain size, roughness, and decreasing with reflectance of AlN films together with increase of color purity and dominant wavelength thin this sense, the property of AlN buffer may strongly govern the characteristic of SAW device using the Mo/ AlN system. (Caicedo et al, 2013) The direct relationship between increased frequency and speed in SAW devices, all this related to the morphological qualities of roughness and grain size favor in increased rate of velocity. The resonance frequency of an SAW is determined by the equation f = V/k, where f is the resonance frequency, V is the phase velocity of the acoustic wave and k is the acoustic wavelength, which in turn is defined by the electrode pitch in the interdigital transducer (IDT).…”