Study of rapid thermal annealing on ultra thin high-k HfO2 films properties for nano scaled MOSFET technology

The effect of rapid thermal annealing on structural and electrical properties of high-k HfO2 ultra thin films deposited by rf-sputtering system is investigated. The films properties were investigated for optimum rapid thermal annealing temperature in oxygen and nitrogen ambient, respectively to get the best electrical results as a MOS device structure. Detailed studies of temperature induced annealing effects on the HfO2/Si interface are done using Fourier Transform Infrared Spectroscopy (FT-IR). The film thickness, composition and microstructure is studied by Ellipsometry, XRD and AFM, respectively, and the effect of annealing on these parameters is shown. The I–V and C–V characteristics of the annealed dielectric film were investigated employing Si/HfO2/Si MOS capacitor structure. The results showed that the HfO2/Si stack with rapid thermal annealing (RTA) in nitrogen ambient showed improved physical and electrical performance than with in oxygen. It is shown that RTA improves the interface properties of HfO2/Si and the densification of HfO2 ultra thin films. The as deposited films were amorphous and orthorhombic after annealed at 700 °C in nitrogen and oxygen, respectively. We found that the nitrogen annealed samples exhibit a reduced equivalent oxide thickness, interfacial density of states, capacitance–voltage hysteresis and leakage current; additionally it also showed negligible charge trapping under positive voltage bias and temperature stress. The results are presented and discussed.

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