Oxide Atomic Layer Deposition Research Articles

Some recent developments in the MOCVD and ALD of high-κ dielectric oxides

A range of high-permittivity (κ) dielectric oxides are currently being investigated as alternatives to SiO2 as the dielectric insulating layer in sub-0.1 μm CMOS technology. Metalorganic chemical vapour deposition (MOCVD) and atomic layer deposition (ALD) are promising techniques for the deposition of these high-κ dielectric oxides. Some recent developments in precursors for the MOCVD and ALD of ZrO2, HfO2, Zr- and Hf-silicate and the rare earth oxides M2O3 (M = Pr, La, Gd, Nd) are discussed.

Flat-band Voltage Study Of Atomic-layer-Deposited Aluminum-oxide Subjected To Spike Thermal Annealing

AbstractHigh-κ dielectrics based the oxide of Al were prepared by atomic layer deposition (ALD) on 200-mm p-type Si wafers. Films were deposited directly on clean Si or on 0.5-nm underlayers of rapid thermal oxide or oxynitrides grown in O2 and/or NO ambients. The purpose of the underlayer films is to provide a barrier for atomic diffusion from the crystal Si to the high-κ dielectric film. Deposited Al-oxide films varied in thickness from 2 to 6 nm. Post deposition anneals were used to stabilize the ALD oxides. Equivalent SiO2-oxide thickness varied from 1.0 to 3.5 nm. In situ P-doped amorphous-Si 160 nm films were deposited over the oxides to prepare heavily doped n-type gate electrodes in MOS structures. Samples were rapid thermal annealed in N2 ambient at 800°C for 30 s, or spike annealed at 950, 1000, and 1050°C (nominally zero time at peak temperature). Flat band voltages, VFB were determined from C-V measurements on dot patterns. The 800°C anneals were used as a baseline, at which the poly-Si electrodes are crystallized and acquire electrical activation while subjecting the high-κ dielectrics to a low thermal budget. Positive shifts in VFB were observed, relative to a pure SiO2 control, ranging from 0.2 to 0.8 V. Spike annealing reduces the VFB shift for ALD films deposited over underlayer films. The VFB shift and the changes with annealing temperature show systematic dependence on the nitridation of the underlayer.

Quantum chemical study of the elementary reactions in zirconium oxide atomic layer deposition

Elementary reactions in atomic layer deposition of zirconia using zirconium tetrachloride and water are investigated using the density functional theory. The atomistic mechanisms of the two deposition half cycles on the Zr–OH and Zr–Cl surface sites are investigated. Both half reactions proceed through the formation of stable intermediates, resulting in high barriers for HCl formation. We find that the intermediate stability is lowered as the surface temperature is raised. However, increasing temperature also increases the dissociation free-energy barrier, which in turn results in increased desorption of adsorbed precursors.

Effect of water dose on the atomic layer deposition rate of oxide thin films

The growth rate and properties of atomic layer deposited (ALD) Al2O3 thin films were examined by varying the water dose in the Al(CH3)3-H2O process at growth temperatures of 150–500°C. When the growth rate was followed as a function of water pulse time, it was found to saturate with both small and large water doses but the saturated level was substantially higher for the large water dose, 1.2 vs. 1.0 Å/cycle. This increase was attributed to an increased hydroxyl group density on the film surface after the water pulse. The effect of the water dose was examined also in other ALD oxide processes where in most cases the growth rate increased by 24 to 86%, in the best cases even doubled, though in a few other cases the effect was minimal. No major differences were found in the properties of the films grown with small and large water doses.

In situ characterization of atomic layer deposition processes by a mass spectrometer

In situ characterization of the chemical reactions in atomic layer deposition (ALD) processes in flow-type reactors is an important and challenging task. For this purpose, a quadrupole mass spectrometer has been integrated to an ALD reactor The special features of this setup are described and its performance is demonstrated by studies on ALD oxide processes employing Al(CH 3 ) 3 , Ti(OC 2 H 5 ) 4 , Ta(OC 2 H 5 ) 5 and Nb(OC 2 H 5 ) 5 as metal precursors and water as the oxygen source.