(Invited) In Situ XPS Study on ALD (Atomic Layer Deposition) of High-k Dielectrics: La₂O₃ Using La-Formidinate and Ozone

Abstract

The detailed growth behavior of lanthanum oxide (La2O3) on a silicon substrate during atomic layer deposition (ALD) is investigated by in-situ, x-ray photoelectron spectroscopy (XPS) following individual ALD pulses of tris(N,N'-diisopropyl-formamidinato) lanthanum [La(iPrfAMD)3] and highly concentrated ozone (~390 g/m3). At the initial growth stage, ozone oxidized the La-ligand as well as the silicon substrate. During oxidation of silicon substrate, a noticeable amount of silicon atoms diffused into growing La2O3 film, resulting in Si-rich and La-rich La-silicates showing composition gradient of La/Si at the deposition temperature of 250 oC. The amount of La-silicate after third ALD cycle reached more than 50 % of that generated by 30 cycles. As the thickness of the film increased with sequential ALD cycles, the substrate oxidation as well as the out-diffusion of Si atoms becomes a negligible quantity, and the pure La2O3 film starts growing leaving La-silicate layers at the interface.

Enhanced Electrical Properties of Atomic Layer Deposited LaxAlyO Thin Films with Stress Relieved Preoxide Pretreatment

“…The Si 2 s spectra were fitted with three Gaussian-Lorentzian line shape peaks, which are at 150.6 (I), 152.2 (II), and 154.0 eV (III). Among the three peaks, peak I corresponds to the chemical bond of Si-Si, originating from Si substrate [18]. Peak II and III, corresponding to La-O-Si and Si-O-Si respectively, are likely present due to the existence of SiO x and La-silicate which are the main components of interfacial layer (IL) between La x Al y O film and Si substrate [19].…”

The influence of process parameters and pulse ratio of precursors on the characteristics of La1 − x Al x O3 films deposited by atomic layer deposition

“…Figure 8b shows O1s XPS spectra of the four asdeposited nanolaminate films. The O1s spectrum was fitted with three peaks (indicated by dashed line) after the application of a Smart background for samples A, B, and C. The dotted lines indicate the binding energy of La-O-La, La-Si-O, and La-OH peaks with the increasing binding energy [22][23][24]. La-O-La peak becomes larger with the increasing La/Al precursor pulse ratio.…”

Selective Growth of Interface Layers from Reactions of Sc(MeCp)2(Me2pz) with Oxide Substrates

“…Oxidation of the Si(100)–H substrate by ozone at 250 °C resulted in the out-diffusion of silicon to form a graded lanthanum silicate interface layer . In a different study, the ALD of La 2 O 3 films on Si(100)–H substrates at 260 °C also resulted in the formation of a silicate layer; this interface layer was thicker when using water (as opposed to ozone) as the coreactant .…”

“…For example, XPS studies revealed the presence of a lanthanum silicate phase resulting from the diffusion of silicon atoms into La 2 O 3 films grown by ALD using a lanthanum formamidinate precursor with either ozone , or water , as the oxidant. Oxidation of the Si(100)–H substrate by ozone at 250 °C resulted in the out-diffusion of silicon to form a graded lanthanum silicate interface layer .…”

“…Oxidation of the Si(100)−H substrate by ozone at 250 °C resulted in the outdiffusion of silicon to form a graded lanthanum silicate interface layer. 32 In situ XPS analysis showed that the lanthanum concentration at the surface gradually increased during the first 30 ALD cycles until a La 2 O 3 composition was achieved; more than half of the silicate generated after 30 cycles was produced by the third cycle. 32 In a different study, the ALD of La 2 O 3 films on Si(100)−H substrates at 260 °C also resulted in the formation of a silicate layer; this interface layer was thicker when using water (as opposed to ozone) as the coreactant.…”