Development of preferred orientation in polycrystalline AlN thin films deposited by rf sputtering system at low temperature

Abstract

The development of preferred orientation in AlN thin films deposited on silica glass substrates by rf sputtering at low substrate temperature (<150 °C) has been studied. The main factors controlling the preferential orientation of the AlN thin films are the ion-bombardment energies, incidence angle of the arriving particles, and deposition rate. At low pressure, a perpendicular and highly directional energetic ion-bombardment induces an orientation of the crystallites with their c-axis perpendicular to the substrate surface. At higher pressure (>15 mTorr), a spreading in the incidence angle of the arriving particles, due to gas phase collisions, favors the formation of AlN crystal twinning. A change in the preferred orientation of the films from (0001) to (1011) for deposition rates above 1.8 Å/s is observed.

Statistical analysis of the effect of deposition parameters on the preferred orientation of sputtered AlN thin films

“…The texture of samples deposited at 0.66 Pa is independent of the power applied to the target, as the small change observed in the texture parameter is statistically not significant. At a pressure of 1.33 Pa the (002) preferred orientation is significantly better at a power of 100 W as compared with samples deposited at 200 W. Lowering the power applied to the target decreases the deposition rate, a condition that promotes the growth of grains with (002) preferred orientation [6]. At 0.66 Pa, physical parameters that are pressure dependent, discussed in the following paragraph, will control the preferred orientation, overshadowing the effects of the power applied to the target.…”

“…In addition, AlN thin films with preferred orientation are potential candidates for the piezoelectric material in surface acoustic wave devices due to its high sound velocity, high resistivity, and high breakdown voltage [1]. AlN thin films have been synthesized by several methods including chemical vapor deposition [2], plasma assisted molecular beam epitaxy [3], laser ablation deposition [4], electron cyclotron resonance [5], and ion beam assisted deposition [6]. Most of these techniques require a substrate with a specific orientation (sapphire or SiC) and a high deposition temperature (1000 -C) in order to obtain the best crystallinity and texture in the deposited film.…”

“…Sputtering techniques, on the other hand, are well suited for microelectronic processing since the typical deposition temperature is lower than 200 -C. In a series of papers published recently it is shown that it is possible to deposit polycrystalline AlN thin films with a biaxial preferred orientation using sputtering techniques [6]. In this biaxial structure there is an ordering of the crystallites with their c-axis perpendicular to the substrate as well as in the plane parallel to the substrate.…”

Structural, chemical, optical and mechanical properties of Au doped AlN sputtered coatings

“…A. Rodríguez-Navarro et al [19] found that for low deposition rate conditions the preferred orientation is after (001) while for higher deposition rates the (101) orientation is observed. Ion bombardment processes greatly…”

“…In spite of the use of glancing mode, the fact that different intensities were found in the samples, with and without gold, suggests that preferential orientations could be related either with the different Al/N ratios or to possible influences of Au incorporation in the adatom mobility of the arriving species to the growing film [16,18,19,20]. In fact, the presence of Au atoms during the film growth stage has most probably interfered with the incorporation of Al-N clusters in the film (as discussed before).…”