Cyclic Chemical-Vapor-Deposited TiO2/Al2O3 Film Using Trimethyl Aluminum, Tetrakis(diethylamino)titanium, and O2

Titanium aluminum oxide films have been studied as potential alternative gate dielectrics. However, most studies have focused on sputtered films. In this study, we demonstrate that a combination of tetrakis(diethylamino)titanium, trimethyl aluminum, oxygen, and cyclic chemical vapor deposition (CVD) is a promising approach for laminated TiO2/Al2O3 films with low impurities and high thermal stability even at low temperatures. The growth of the films is carried out in a cold-wall CVD chamber at 300°C and 0.7 Torr. Our studies show that the properties of TiO2 improve with the addition of even a few percent of Al2O3. X-ray diffraction analyses indicate that as-deposited TiO2/Al2O3 films have amorphous structure. Upon annealing as-deposited films in Ar at 700°C for 5 min, TiO2/Al2O3 films maintain their amorphous structure, while pure TiO2 films crystallize at these conditions. Atomic force microscopy shows that the surfaces of TiO2/Al2O3 films are smoother than those of TiO2 films deposited at the same conditions. Even though annealing increases the roughness of the TiO2/Al2O3 films, film roughness is still significantly lower than that of as-deposited TiO2 films. Moreover, Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy show that there is no detectable formation of interfacial silicon oxide and negligible carbon impurity in as-deposited TiO2/Al2O3 films.