| Summary: | 碩士 === 國立高雄應用科技大學 === 電子工程系 === 97 === Recently, the thickness of gate oxide made from SiO2 in nano-scale MOSFET has reached a physical limit according to the current leakage. The High-K dielectric materials have been found to be a good solution to the problem. However, there is a tradeoff between the dielectric constant and the energy gap in High-K materials, a larger dielectric constant usually associated with a smaller energy gap. To solve this problem a multilayer structure is adopted, for example a TiO2 grown on HfO2. In this work, an alloy oxide of Hf(1-X)TiXO2 is studied because the properties of TiO2 are complementary to HfO2.
The density function theory (DFT) with the DMol3 and CASTEP codes is applied to investigate High-K alloy dielectric materials of Hf(1-X)TiXO2 and Hf(1-X)TiXOY. The mix-atom mode is used to model the alloy oxide. In out study, we find that (i) the position of minority atoms strongly affects the physical properties of bulk material, (ii) the high Ti concentration is easier to produce oxygen vacancies than the low concentration, and (iii) the increase of the Ti concentration decreases the energy gap but increases the dielectric constant. According to these properties, the Hf(1-X)TiXO2 may have possibility to be used as a High-K dielectric layer in nano-scale MOSFET.
|
|---|
