Dispositivos de ondas acústicas de superfície com base em filmes de nitreto de alumínio depositados por processos a plasma

Abstract

The study of thin films of aluminum nitride (AlN) and devices constructed involving surface acoustic waves (SAW) technology is complex. However, this work serves as a basis for the development of SAW devices, such as filters with high selectivity, resonators, identification tags, delay lines, pulse compressors, different sensors (pressure, temperature, biosensors). Devices constructed on AlN films use wireless technology and are capable of operation in harsh environments without suffering degradation. The activity took place on four fronts: the first one refers to the synthesis of AlN thin films, and aimed at the establishment of criteria to characterize the deposition of AlN films by reactive RF magnetron sputtering; the second concerns the application of the techniques of analysis by X-ray diffraction (XRD), infra-red spectroscopy with Fourier transform (FTIR), Raman spectroscopy, profilometry and spectroscopy by Rutherford backscattering (RBS); the third front refers to the project of new SAW devices and Photolithography; the fourth is the acoustic characterization using a network Analyzer, and aimed at the determination of the SAW velocity, electromechanical coupling coefficient and frequency response of the devices. This work performed a study of the main problems involved in the deposition of aluminum nitride films, with good texturing AlN (100), and highly crystalline. It was studied the influence of the high SAW velocity of AlN films on the manufacture of SAW devices. The main characteristic parameters of the SAW devices performance, manufactured in the delay line configuration, were analyzed. It was suggested a new method of estimation of SAW speed based on the impulse response of the devices constructed. Hence this new method is more extensive than those found in the scientific literature. The results of the analysis of AlN films are consistent with those found in specialized literature. It was possible to construct SAW devices based on the AlN(100)/Si(100) structure. The SAW devices showed a satisfactory response in the frequency domain and their characteristic parameters were determined.