Annealing of Al₂O₃thin films prepared by atomic layer deposition

Abstract

Amorphous Al2O3 thin films were deposited on a Si (1 1 1) substrate at 150 °C in oxygen-rich conditions by atomic layer deposition. Rapid thermal annealing was performed at high temperatures, ranging from 1000 to 1200 °C, to study the crystallization characteristics of the Al2O3 films. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy, atomic force microscopy and frequency-dependent capacitance measurements were used to characterize the structural and electrical properties before and after the annealing. It was found that the best crystallization of the Al2O3 film was achieved after annealing at 1150 °C, corresponding to a minimum of full width at half maximum (FWHM) of the Al2O3 (012) XRD peak and the maximum of surface roughness and the capacitances. This suggests that 1150 °C is the optimal transition temperature from amorphous to crystalline and to get the best insulating property for Al2O3 thin film. The formation of the SiO2 interfacial layer after annealing has been observed by HRTEM for the annealed sample, accompanied by a decrease in the thickness of Al2O3 films.

Annealing effects on the optical and structural properties of Al2O3/SiO2 films as UV antireflection coatings on 4H-SiC substrates

“…4(a)-(d), the grain size appeared to increase gradually with temperature, which may due to highertemperature annealing gathered more atoms together from available neighboring sites. The identical phenomena were also reported previously [13,15]. Fig.…”

“…The RMS roughness of the as-deposited film was larger than that of the annealed films, which may be attributed to the variation of film stress [14]. Then, the RMS roughness began to increase slightly when the annealing temperature increased, which agreed with previous reports [15], as shown in Fig. 5.…”

“…It may be due to more thermally activated atoms filled the voids and diffused with each other when the annealing temperature increased, which made the films denser and reduced the film thicknesses. Zhang et al [15] reported that the excess oxygen atoms in the Al 2 O 3 film diffused into the substrate during the annealing, decreasing the Al 2 O 3 thickness. We found the result in the XPS analysis.…”

pH Response of Silicon Nanowire Sensors: Impact of Nanowire Width and Gate Oxide

“…For example, we can gate the NW asymmetrically and thereby accumulate more carriers at the top surface as compared with the bottom surface, or vice versa. It is also known that surfaces with different crystallographic orientations have different band alignments; (21) hence, the accumulation of carriers may start differently at different crystal faces. Since a detailed systematic study of these variabilities is beyond the scope of this work, we assume that the current scales with the top perimeter, i.e., W eff = W top + 2W side .…”

“…However, the ALD oxides have a large excess of O 2 as they are grown in an oxygen-rich environment. Therefore, there is the risk that during the postannealing, the excess O 2 diffuses to the Si where it leads to the growth of the interfacial SiO 2 layer (20,21) that already formed between the Si substrate and the ALD oxide during the ALD deposition. (20) The smaller dielectric constant of 3.9 for SiO 2 will reduce the total dielectric constant of the ALD layer.…”