Reaction Chemistry during the Atomic Layer Deposition of Sc₂O₃ and Gd₂O₃ from Sc(MeCp)₃, Gd(ⁱPrCp)₃, and H₂O

Abstract

The reaction chemistry during the atomic layer deposition (ALD) of Sc2O3 and Gd2O3 from Sc(MeCp)3, Gd(iPrCp)3, and H2O was investigated by in situ time-resolved quadrupole mass spectrometry. Despite the similarity of the ligands of the Sc and Gd precursors, the growth characteristics and ligand dissociation patterns of the Sc2O3 and Gd2O3 ALD processes showed considerably different behavior. For both processes, the precursors reacted with the hydroxylated surface by proton transfer and release of the protonated ligand. The remaining ligands were then removed by hydrolysis during the H2O pulse. However, for the Sc(MeCp)3/H2O process, ∼56% of MeCpH was released during the Sc(MeCp)3 exposure, whereas in the case of the Gd(iPrCp)3/H2O process, as much as 90% of iPrCpH was released during the Gd(iPrCp)3 pulse. The observation that almost all iPrCp ligands were removed during the initial Gd(iPrCp)3 absorption step can be ascribed to CVD-like reactions between the Gd(iPrCp)3 precursor and excess hydroxide or physisorbed H2O on the hygroscopic Gd2O3 surface. The influence of the growth temperature on the ligand exchange behavior and the resulting film properties (thickness uniformity, impurity concentration) was studied in the temperature range between 200 and 350 °C. In addition, the transient growth behavior of Gd2O3 on Sc2O3 and vice versa was studied, indicating that the hygroscopic nature of Gd2O3 also strongly influences the deposition of Gd x Sc1–x O3 ternary oxides.

Ozone‐Based Atomic Layer Deposition of Gd2O3 from Tris(isopropyl‐cyclopentadienyl)gadolinium: Growth Characteristics and Surface Chemistry

“…The GPC map over the full wafer indicates that the deposition occurred preferentially at the gas inlet of the cross‐flow reactor. This is reminiscent of the H 2 O‐based ALD process where the strong hygroscopicity of Gd 2 O 3 led to hydroxide formation as well as to sorbed H 2 O and, as a consequence, to parasitic CVD and rapid precursor exhaustion near the inlet . Accordingly, the GPC at points close to the gas inlet reached values of >0.4 nm, which are very large for steric hindrance limited ALD using Gd( i PrCp) 3 .…”

“…The understanding of the ALD surface chemistry and the relation with film and deposition process properties are keys to the successful integration of Gd 2 O 3 thin films in micro‐ or optoelectronic devices . Recently, we have reported on the surface chemistry of Gd 2 O 3 ALD from Gd( i PrCp) 3 and H 2 O . A major complication was the strong hygroscopicity of Gd 2 O 3 , which led to parasitic chemical vapor deposition (CVD) due to sorbed H 2 O.…”

Atomic layer deposition of scandium‐based oxides

“…We have confirmed these saturation characteristics in Gd x Sc 2− x O 3 layers, of which the supercycle consisted of two Gd( i PrCp) 3 /H 2 O and one Sc(MeCp) 3 /H 2 O subcycles. The surface chemistry of these subcycles has also been examined by in situ time‐resolved quadrupole mass spectrometry (QMS) .…”

Incomplete elimination of precursor ligands during atomic layer deposition of zinc-oxide, tin-oxide, and zinc-tin-oxide

“…However, the composition and combined growth rate during multi-element ALD typically deviate from what is expected from the growth rates of the binary processes, an observation that has been explained in many cases by nucleation effects when switching from one binary process to the other. [6][7][8][9][10][11] Various theories for these deviating trends have been proposed, such as the a) E-mail: sbent@stanford.edu contribution of etching reactions, 9 differences in reactive site densities between the two binary metal-oxide surfaces, 12 or the occurrence of ligand exchange from an adsorbed precursor molecule to a metal surface atom. 13 The deposition of zinc-tin-oxide (ZTO) by ALD has been investigated more extensively than most ternary ALD processes because of its potential applications.…”