Atomic-layer-deposited Al2O3 thin films with thin SiO2 layers grown by in situ O3 oxidation

The growth, thermal annealing behaviors, and electrical properties of Al2O3 thin films grown by atomic layer deposition (ALD) on bare (100) Si and various oxidized Si wafers, by in situ O-3 oxidation at 400degreesC and ex situ rapid thermal annealing (RTA) under O-2 atmosphere at 900 degreesC, were investigated. The ALD process was performed using Al(CH3)(3) and high concentration of O-3(400 gm(3)). The high oxidation potential of O-3 oxidized the Si surface at a very early stage of film growth and eliminated the incubation period even on a bare Si surface. The as-grown Al2O3 films had excess oxygen in the films, which diffused to the film Si interface and increased the interfacial layer by oxidizing the Si substrates during postannealing. The Al2O3 films grown on a bare Si substrate had the highest concentration of excess oxygen which resulted in the largest increase in the interfacial layer thickness during postannealing. As a result, the initial oxidation of the Si wafer did not significantly decrease the capacitance density compared to the films grown on a nonoxidized Si wafer at the as-deposited and postannealed states. Therefore, the Al2O3 layers grown using a high concentration of O-3 oxidant on the in situ O-3 oxidized Si wafers showed real high-k gate dielectric performance although the dielectric constants of the Al2O3 films were rather small (similar to9) compared to other high-k gate dielectric films. (C) 2004 American Institute of Physics.