| With the rapid development of ultra large scale integrated circuit, the device feature size continues to reduce. When the feature size down to 65nm or less, the traditional gate dielectric thickness must be less than 1.4nm.Such thin SiO2 layer of the device resulted in substantial increase of power consumption and decrease gate voltage control of channel capacity. To maintain the same equivalent oxide thickness, through increasing the physical thickness of the dielectric layer, the use of high dielectric materials instead of traditional gate dielectric, and thus greatly reduce direct tunneling effect, increase the stability of the device. So to find new high-K gate dielectric material has become an international new research project. In the current study, high-k gate dielectric Ta2O5 film is seen as a new generation of dynamic random access memory (DRAM) capacitor component materials of promising alternatives for its high dielectric constant (K-25), compatible with conventional Si technology, and other prominent advantages. Therefore, the study of the performance of Ta205 thin films is useful and has got widespread concerned.In this article Ta205 gate dielectric films were prepared by RF sputtering. We study the effect of annealing temperature and oxygen argon flow ratio on the gate dielectric film properties and electrical properties. The leakage current mechanism was also explained.The main research contents of this paper are depicted as follow:1. Different annealing temperatures affect the Ta2O5 gate dielectric properties. The results show that the crystallization of Ta2O5 films beginning at 700℃. The 400℃treatment film reached maximum dielectric constant, because the influence of annealing temperature on the dielectric constant has two main aspect, on the one hand, with the increasing annealing temperature, the film becomes higher crystallization, the dielectric constant increases. On the other hand, as the annealing temperature increases, the interface layer becomes thicker, leading the dielectric constant decrease.400℃anneal treatment leads to the maximum dielectric constant and the minimum leakage current density of films, because when the films are applied the high annealing temperature, charge trapping in the oxide layer will gradually disappear, all kinds of defects will be reduced, so the leakage current will decrease. In addition, the annealing temperature makes the films become polycrystalline from the amorphous state, which is equivalent to the role of grain boundary defects, leakage current will increase.700℃leads the result of minimum leakage current density of films.2. Different oxygen argon flow ratio affect on film properties. With increasing oxygen flow ratio of argon, deposition rate gradually decreased. When the oxygen argon flow ratio 1:4, the film reached the minimum of leakage current density, because when the oxygen flow rate as active gas increases. The generated interface layer thickness also increases, and the presence of interfacial layer will increase the leakage current.3. The leakage current mechanism of argon gas to oxygen ratio of 1:4 mixture samples are analyzed. The study found at different voltage range, the leakage current mechanism are different. When negative voltage between -1.56V and -0.25V applied the gate, the leakage current is mainly caused by the Schottky emission. When applied a positive voltage between 0.06V and 0.81V on the gate, the leakage current is mainly caused by the Schottky emission. Applied a positive voltage above 0.81V or below-1.56V to the gate, the leakage current is mainly caused by the F-P emission. |
PDF Full Text Request