Abstract
In this MS thesis, we employed the molecular beam epitaxy (MBE) method to deposit amorphous HfO2 dielectrics (k = 15) on silicon. Based on extensive characterizations including RHEED and TEM, we have demonstrated for the first time an atomically abrupt HfO2/Si interface free of SiO2 or silicate formation. In addition, TiN electrode was deposited by reactive sputtering from a pure Ti target in Ar/N2 plasma. To improve the thermal stability of the films, pure titanium metal was deposited to form the capping layer and we found that almost no crack on the film surface when samples were subjected to high temperature annealing (~850oC). The resistivity of Ti/TiN was decreased when increasing the temperature. Furthermore, the thermal stability of high-k gate dielectric MOS capacitors with Ti/TiN as the metal gate (Ti/TiN/HfO2/Si) was studied. We found the leakage current densities of samples after annealing at 850oC was eight orders of magnitude larger than that of as deposited samples, which may result from the recrystallization of HfO2 film. However, all the samples showed lower leakage current densities compared to that of SiO2 at the same EOT. On the other hand, we found the capacitors showed good performance even though the temperature was up to 700oC, but a degradation in electrical characteristics at 850oC. The lowest EOT achieved for this structure was 1.53 nm. Moreover, the Dit of the sample increased when the temperature was raised from 600oC to 700oC, but it decreased when the temperature was further increased to 800oC. The value of Dit was ranging from 1012 to 1013 ev-1cm-2. For MOSFET process, a simple fabrication steps using lift-off process were established. The reasonable electrical characteristics of the MOSFET have been performed and the best transconductance, about 48.5mS/mm, was obtained when the activate temperature was at 700oC.