Studies on Wet-Chemical Surface Conditioning for Al2o3 Passivation Layers Deposited with ALD

In order to enhance the passivation quality of thin Al2O3 layers in an Al2O3/SiNx stack an appropriate pre-deposition cleaning and wet-chemical surface conditioning plays an important role. In this study we present findings on the influence of wet-chemical surface conditioning on the passivation quality of thin ALD Al2O3 layers in an Al2O3/SiNx stack. Differently terminated sample surfaces have been investigated. Two different wet-chemical oxides, a HF last step as well as a native grown oxide of an out-of-box wafer have been analyzed regarding their impact on the passivation quality. Also the hydrophilic properties of the surface without a dielectric passivation layer have been measured. We find a direct correlation of the hydrophilic properties and passivation quality of the surface termination on the passivation quality of the Al2O3/SiNx stack. So far, a 60 s HF last step was found to be the best surface treatment for 5 nm Al2O3 layers. In comparison, a surface conditioning by wet-chemical oxides leads to lower lifetimes. In contrast native oxides grown on cleaned wafers were found to enhance the homogeneity and the passivation quality of Al2O3/SiNx stack systems with 0.5 nm Al2O3 layers significantly. Thereby the firing stability of the stack system is not affected.