Structural Properties of AlN Grown on Sapphire at Plasma Self-Heating Conditions Using Reactive Magnetron Sputter Deposition

Abstract

Aluminum nitride (AlN) films were grown on sapphire by reactive magnetron sputter deposition in N 2 discharges at plasma self-heating conditions. The growth temperature was as low as 94°C. The structural properties resulting from different substrate biases and growth pressures were investigated by atomic force microscopy, x-ray diffraction (XRD) measurements, and transmission electron microscopy (TEM). At 20 mTorr of N 2 with most sputtered species thermalized, films exhibited both AlN (0002) and ð1011Þ XRD peaks, with the AlN (0002) intensity initially increasing with ion energy above 15 eV, showing enhanced film quality with an optimum of 25 eV. At a lower growth pressure of 5 mTorr with energetic sputtered species, the AlN ð1011Þ peak disappeared and the crystallinity of AlN improved, exhibiting relaxed epitaxial AlN. The measured lattice parameter was 0.4975 nm, which was 0.10% smaller than that of bulk. The epitaxial relationship of a single-crystal AlN film was confirmed by pole figure and cross-sectional TEM. These results demonstrate that control of ion energy and energy of the sputter-deposited species is critical for film deposition at low temperature.

Two-step method for the deposition of AlN by radio frequency sputtering

“…3), reaching a best value of 1.25°. The improvement of the structural quality with negative bias can be attributed to an increase of the kinetic energy of the impinging ions, hence increasing the mobility of the adatoms at the growing surface [24]. This is consistent with the observed increase of the grain size, as it is shown in the inset of Fig.…”

“…The improved compactness of the layers is attributed to the enhancement of the adatom mobility induced by the increased ion kinetic energy [24]. For substrate bias above this value, the estimated film density decreases to~2.73 g/cm 3 probably due to a change in layer stoichiometry.…”

Comparison of mechanical properties and composition of magnetron sputter and plasma enhanced atomic layer deposition aluminum nitride films

“…III C). 3,11 The densities of sputtered AlN films were the highest on the (100) Si substrate, while on the Al substrate, the sample S_Ti/Al, AlN had a density of 2.85 g/cm 3 which compares to the PEALD film having the highest density, 2.90 g/cm 3 . The sample S_Ti/Mo showed a density of 3.15 g/cm 3 .…”

“…3,11 The densities of sputtered AlN films were the highest on the (100) Si substrate, while on the Al substrate, the sample S_Ti/Al, AlN had a density of 2.85 g/cm 3 which compares to the PEALD film having the highest density, 2.90 g/cm 3 . The sample S_Ti/Mo showed a density of 3.15 g/cm 3 . These results show that the chosen substrate has a significant effect on the density of the sputtered AlN, while the nanoscale roughness remained practically constant (∼2.0 nm) indicating thus the similar size of surface crystallites.…”

“…These demands in turn dictate the most appropriate method of deposition. Therefore, AlN has been grown with several deposition methods, such as sputter deposition, 3 metalorganic chemical vapor deposition, 4 molecular beam epitaxy, 5 plasma enhanced chemical vapor deposition, 6 and plasma enhanced atomic layer deposition (PEALD). 7,8 Despite this, there is a lack of systematic comparison between the two main thin film deposition types: physical vapor deposition (PVD) and chemical vapor deposition (CVD) methods of AlN.…”