Low Temperature Fabrication of High-Permittivity Gate Insulating Film and Its Functional Evaluation for Next Generation LSI.

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This subject aims to establish the process for the stacked structure having the SiO_2 equivalent oxide thickness(BOT) of less than 2.0nm by the plasma oxidation and nitridation using electron cyclotron resonance(ECR) plasma and by the ECR-sputtering of ZrO_2. In order to do that, We investigated the effects of gas flow rate and substrate bias on the structural and electrical properties of SiO_2,SiN,and ZrO_2 thin, films, and clarified the growth mechanism. The obtained results are summarized as follows :(1)The Kr gas is better than Ar to dilute the O_2 plasma for Si oxidation according to the current-voltage characteristics of the Si oxide film. Under the optimum condition, the as-grown Si oxide film at 130℃ shows breakdown electric field of 10-12MV/cm and interface states density of 3.2×10^<10> eV^<-1>cm^<-2>.(2)The nitrogen partial pressure has decisive effect on the film quality. A Si nitride film having a structure nearest to stoichiometric construction is obtained by precise control of N_2 mixing ratio at 60%. Under this optimum condition, SiN film grown at 400℃, having EOT of 2.46nm, shows a leakage current more than two orders of magnitude lower than that of thermal grown SiO_2 having the same EOT.(3)SiN film was deposited Al and then annealed at 450℃ for 30min after SiN growth by using method (2). EOT of the SiN film decreased up to 1.8nm, and the leak current and interface states density were decreased remarkably.(4)The electrical properties of the deposited ZrO_2 films were very sensitiye to the O_2 flow rate and the dielectric breakdown field of 3-5 MV/cm was achieved under the optimum condition. The permittivity was 20.5 and an interfacial Si oxide layer was 2.3nm.(5)The EOT having 1.8nm was achieved by using the stack structure of ZrO_2/SiN/Si, which shows a leakage current more than three orders of magnitude lower than that of thermal grown SiO_2 having the same EOT.