Reactive sputter deposition of highly oriented AlN films at room temperature
- PDF / 167,815 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 0 Downloads / 230 Views
Textured as well as epitaxial thin AlN films are of great interest for a wide range of electro-acoustic and optoelectronic applications. Reduction of the deposition temperature is of vital importance in a number of applications due to thermal budget limitations. In this work we systematically studied the influence of the process parameters on the film properties and identified the factors leading to improved film quality as well as reduced deposition temperature with pulsed direct current sputtering in an Ar/N2 atmosphere. We demonstrated that fully textured (0002) films can be grown under a wide range of conditions. At the same time the full width at half-maximum (FWHM) of the rocking curve of the (0002) XRD peak was found to vary systematically with process conditions—depostion rate, process pressure, gas composition, and substrate temperature. The best films showed a FWHM of 1.2°. We found that by far the most important factor is the arrival energy of the sputtered Al atoms, which is primarily controlled by the process pressure. We report for the first time that fully textured AlN films with a FWHM of under 2° can be grown at room temperature. Other important factors are the ion and electron bombardment of the films and substrate temperature as well as gas composition, although their influence is not as dramatic. Generally, the film quality increases with temperature. Bias and electron bombardment within a certain range also lead to better films.
I. INTRODUCTION
Surface acoustic wave (SAW) and bulk acoustic wave (BAW) electro-acoustic devices are widely used today in a variety of applications both in consumer electronics as well as in specialized scientific and military equipment ranging from mobile phones to TVs, VCRs, keyless entry systems, cordless headphones, alarm and security systems, sensors, etc. By far the most important SAW and BAW devices are transversal filters, low or medium loss intermediate filters, resonators, impedance element filters (IEF), reflective array compressors (RACs) and tags. Wright1 gives a comprehensive compendium of various design approaches that have been proved to be successful in large-scale production. For conventional SAW devices, piezoelectric materials with relatively low phase velocity between 2500 and 4500 m/s, such as quartz, LiNbO3 and LiTaO3 are used. The center frequency of the device is determined by the simple relation Vph ⳱ f × , where Vph denotes the phase velocity, and f and are the frequency and the wavelength, respectively. The wavelength is determined by the distance between a)
e-mail: [email protected] J. Mater. Res., Vol. 17, No. 6, Jun 2002
http://journals.cambridge.org
Downloaded: 16 Jul 2014
the fingers of the interdigital transducers (IDT) used to excite the acoustic wave. Thus, high-resolution lithography and/or the use of high acoustic velocity materials are two main approaches for the fabrication of highfrequency SAW devices. The first one, however, results in an increased fabrication cost while the second one is limited to the choi
Data Loading...
