Impact of ozone concentration on atomic layer deposited HfO2 on GaAs

Effect of ozone (O"3) concentration (90, 300g/Nm^3) on atomic layer deposition of HfO"2 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 O"3 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 (HfO"2) layer experienced shrinkage of ~12% due to densification. However HfO"2 film deposited using O"3 concentration of 300g/Nm^3 produced relatively thicker IL and thinner high-k layer which both did not show a noticeable change after PDA. This led to C"m"a"x variations depending on the different O"3 concentration. In the case of O"3 concentration of 90g/Nm^3, increase of leakage current density by an order was observed and corresponding micro-structural change is discussed.