Deposition and characterization of zirconium tin titanate thin films as a potential high- k material for electronic devices

Abstract

There is considerable need for study of new high dielectric constant ( k) materials to replace SiO 2 in the manufacture of future CMOS logic and storage devices. Current work has focused primarily on binary metal oxides and silicates. In this work, thin films of zirconium tin titanate (ZTT) were deposited by chemical vapor deposition (CVD) using a precursor solution of zirconium tert-butoxide, tin tert-butoxide, and titanium tert-butoxide. The precursor was delivered to a reactor using direct liquid injection. The precursor is mixed such that the relative ratio of the components in the solution is at or near the desired cation ratio of the films. NMR analysis of the precursor solution and each of the individual components suggests that the components in the mixture do not interact (i.e. no ligand exchange). Compositional analysis of the films correlates to the composition of the precursor within a range of values; composition of films deposited from a given precursor composition varies with deposition temperature. The zirconium content of deposited films has been shown to decrease with increasing temperature; the titanium content increases with increasing deposition temperature, while the tin content remains relatively constant with temperature. Kinetic studies of ZTT deposition rate indicate an effective activation energy of 38.8±5 kcal/mol. Depending on processing parameters, dielectric constants of ZTT films were shown to range from 21 to 36 with no post-deposition anneal.