Impact of ozone concentration on atomic layer deposited HfO2 on GaAs

Effect of ozone (O3) concentration (90, 300 g/Nm3) on atomic layer deposition of HfO2 thin films on GaAs wafers using tetrakis (dimethylamino)hafnium (TDMAHf) as Hf precursor was systematically studied including MISCAP performance and related microstructure. High-resolution transmission electron microscopy analyses show that oxidation of the GaAs substrate enhances with O3 concentration which leads to an increase in interfacial layer (IL) thickness between the high-k dielectric and the substrate. The thin IL was maintained after PDA, while the high-k (HfO2) layer experienced shrinkage of ∼12% due to densification. However HfO2 film deposited using O3 concentration of 300 g/Nm3 produced relatively thicker IL and thinner high-k layer which both did not show a noticeable change after PDA. This led to Cmax variations depending on the different O3 concentration. In the case of O3 concentration of 90 g/Nm3, increase of leakage current density by an order was observed and corresponding micro-structural change is discussed.

It is shown that the HfO2 deposited using lower O3 concentration exhibited thinner interfacial layer. The thin interface was maintained after PDA. Significant increase in Cmax was observed for HfO2 film prepared using lower O3 concentration. However, increase of leakage current density by over an order was a trade-off. It is suggested that during annealing, relative deficiency of oxygen in the HfO2 film and remarkably thin interface of lower O3 concentration played a key role, and are exploited by substrate elements which are likely to diffuse into the HfO2.Figure optionsDownload as PowerPoint slideHighlights
► Atomic layer deposited hafnium oxide high-k dielectric layers are studied.
► TDMAHf and ozone is used as precursors.
► Two different concentrations of ozone were compared.
► MISCAP characteristics and microstructure analyses are discussed.