Thermally stable ultra-thin Zr silicate for CMOS applications

With the dramatic scaling of CMOS devices, numerous metal oxides and silicates with high dielectric constants are being pursued intensely to replace conventional SiO₂ as gate dielectrics. Among them, ZrO₂ and its silicates are considered to be the most promising candidates. In this study, we report on the electrical and physical properties of ultra-thin Zr Silicate/ZrO₂ films deposited by the jet-vapor-deposition (JVD) process. It is shown that films with equivalent oxide thickness (EOT) of 1 nm, with high thermal stability, low leakage and good electrical properties can be fabricated. Our analysis also shows that the compositions of JVD films vary with the thickness. Thinner films are found to be Zr-silicate-like, whereas thicker films appear to be graded with a transition to stoichiometric ZrO₂. The presence of a Zr silicate interfacial layer may prevent the formation of interfacial SiO₂, despite the fact that as-deposited films are found to be oxygen rich. In contrast to other ZrO₂ films reported in the literature, the EOTs of our films decrease after post deposition annealing. Another remarkable observation is that the JVD Zr silicate film can survive an annealing temperature as high as 1000°C, suggesting that it can be used in a conventional CMOS process without the need for a replacement gate process