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Atomic layer deposition (ALD) is used in applications where inorganic material layers with uniform thickness down to the nanometer range are required. For such thicknesses, the growth mode, defining how the material is arranged on the surface during the growth, is of critical importance. In this work, the growth mode of the zirconium tetrachloride/water and the trimethyl aluminum/water ALD process on hydrogen-terminated silicon was investigated by combining information on the total amount of material deposited with information on the surface fraction of the material. The total amount of material deposited was measured by Rutherford backscattering, x-ray fluorescence, and inductively coupled plasma–optical emission spectroscopy, and the surface fractions by low-energy ion scattering. Growth mode modeling was made assuming two-dimensional growth or random deposition (RD), with a “shower model” of RD recently developed for ALD. Experimental surface fractions of the ALD-grown zirconium oxide and aluminum oxide films were lower than the surface fractions calculated assuming RD, suggesting the occurrence of island growth. Island growth was confirmed with transmission electron microscopy (TEM) measurements, from which the island size and number of islands per unit surface area could also be estimated. The conclusion of island growth for the aluminum oxide deposition on hydrogen-terminated silicon contradicts earlier observations. In this work, physical aluminum oxide islands were observed in TEM after 15 ALD reaction cycles. Earlier, thicker aluminum oxide layers have been analyzed, where islands have not been observed because they have already coalesced to form a continuous film. The unreactivity of hydrogen-terminated silicon surface towards the ALD reactants, except for reactive defect areas, is proposed as the origin of island growth. Consequently, island growth can be regarded as “undesired surface-selective ALD.” [ABSTRACT FROM AUTHOR]

In this work, we have studied the TMA/H2O (TMA = Al(CH3)3) atomic layer deposition (ALD) of Al2O3 on hydroxyl (OH) and thiol (SH) terminated semiconductor substrates. Total reflection x-ray fluorescence reveals a complex growth-per-cycle evolution during the early ALD reaction cycles. OH and SH terminated surfaces demonstrate growth inhibition from the second reaction cycle on. Theoretical calculations, based on density functional theory, are performed on cluster models to investigate the first TMA/H2O reaction cycle. Based on the theoretical results, we discuss possible mechanisms for the growth inhibition from the second reaction cycle on. In addition, our calculations show that AlCH3 groups are hydrolyzed by a H2O molecule adsorbed on a neighboring Al atom, independent of the type of backbonds (Si-O, Ge-O, or Ge-S) of AlCH3. The coordination of Al remains four-fold after the first TMA/H2O reaction cycle. [ABSTRACT FROM AUTHOR]

To increase complementary metal oxide semiconductor (CMOS) device performance, new materials are introduced in the gate stack (high-k dielectrics and metal gates) and the transistor channel (Ge, Ill-V materials). In this work we study the atomic layer deposition (ALD) of hafnium oxide on Ge and GaAs substrates. Passivation layers are required to achieve a sufficiently low interface state density, but these might also influence the growth behavior and dielectric quality. Therefore, we investigate the effect of surface preparation, for example, native oxide, wet clean, thermal oxidation, and S-passivation. for the HfCI4/H2O and tetrakis diethylamino hafnium = ((C2H2)2N)2Hf (TDEAH)/H2O processes. The growth of HfO2 from initial submonolayer coverage to continuous HfO2 film is studied by means of Rutherford backscattering, static time-of-flight secondary ion mass spectroscopy, and X-ray photoelectron spectroscopy. HfCl4/H2O ALD depends on the surface preparation. The growth is enhanced on oxide surfaces (thermally grown GeO2, HF-cleaned Ge, and GaOx-AsOy) and inhibited on oxide-free substrates (HBr-cleaned Ge). The initial island growth regime is least pronounced on germanium oxide. In contrast, TDEAH/H2O ALD is independent of the surface preparation. The growth is inhibited in the first ∼20 cycles on native oxide and S-passivated GaAs [(NH4)2S treatment], but the initial island growth regime is quickly followed by the two-dimensional growth regime. [ABSTRACT FROM AUTHOR]

In this paper, an effective technique and methodology for the estimation of fixed charge components in high-k stacks was demonstrated by varying both the SiO2 and high-k dielectric thicknesses. The SiO2 thickness was scaled on a single wafer by uniformly changing the etch time of a thermally grown SiO2 layer across the wafer. This minimized wafer-to-wafer variations and enables acquisition of statistically significant datasets. Layers with different thickness of both the nitrided and non-nitrided hafnium-silicate layers were then grown on these wafers to estimate all the interfacial and bulk charge components. The reproducibility and validity of this technique were demonstrated, and this method was used to compare the fixed charge levels in Hf-silicates (HfSiO) and nitrided-Hf-silicate (HfSiON) layers. [ABSTRACT FROM AUTHOR]

In search of a proper passivation for high-k Ge metal-oxide-semiconductor devices, the authors have deposited high-k dielectric layers on GeO2, grown at 350–450 °C in O2. ZrO2, HfO2, and Al2O3 were deposited by atomic layer deposition (ALD). GeO2 and ZrO2 or HfO2 intermix during ALD, together with partial reduction of Ge4+. Almost no intermixing or reduction occurs during Al2O3 ALD. Capacitors show well-behaved capacitance-voltage characteristics on both n- and p-Ge, indicating efficient passivation of the Ge/GeOx interface. The density of interface states is typically in the low to mid-1011 cm-2 eV-1 range, approaching state-of-the-art Si/HfO2/matal gate devices. [ABSTRACT FROM AUTHOR]