| Summary: | 碩士 === 國立清華大學 === 電子工程研究所 === 94 === In this MS thesis, we employed the molecular beam epitaxy (MBE) method to deposit amorphous HfO2 dielectrics (k = 15) on silicon. We have demonstrated for the first time an atomically abrupt HfO2/Si interface free of SiO2 or silicate formation. In addition, TiN metal gate was deposited by reactive sputtering from a pure Ti target in Ar/N2 plasma. A two-steps annealing studies were carried out to improve the electrical performance of high-k gate dielectric MOS capacitors. The interface trap density (Dit) were calculated by Terman method to be 1E12 eV-1cm-2. Furthermore, the thermal stability of TiN/MBE-HfO2 gate stack was studied. We found the gate leakage current could be attributed to the re-crystallization of the HfO2. We also found the capacitance was decreased after higher annealing temperature (600~800oC). It indicated the formation of low-κ interfacial layer. We could use a TiN/Ti/HfO2 gate stake to achieve smaller EOT. The Ti layer acted as a buffer to enhance the accumulation capacitance. In order to increase the re-crystallization temperature of the HfO2, we use MBE technique to deposit the HfO2 doped with 20% Y2O3. The Y2O3 doping leading to increased activation temperature and dielectric constant. Then a better device performance was achieved. Another approach on the dielectric using HfO2 had been carried out by combining MBE and ALD techniques. Prior to ALD-grown HfO2, a template of HfO2 (2nm) was deposited by MBE first. That’s the first time we use this method to grow the gate dielectric. As we expect, a MOSFET with such gate oxide displays excellent results. A ID of 240 mA/mm and gm of 120 mS/mm were attained, which were much better than that of simply ALD-grown case and comparable to the data reported by other major groups.
|
|---|
