Characteristics of LaAlO3 as insulating buffer layers of ferroelectric-gate field effect transistors

LaAlO3 films were prepared on Si (100) substrates by an electron cyclotron resonance (ECR)-sputtering method, with the aim of using these films as an insulator layer in the metal-ferroelectric-[metal-]insulator-semiconductor (MF[M]IS) structure. In the characterization of the films, particular attention was paid to the comparison with Al2O3 with the same equivalent oxide thickness (EOT). It was found that electrical properties such as maximum induced charge density, long-term reliability, time-dependent dielectric breakdown, and so on were superior in LaAlO3 than in Al2O3 with the same EOT. It was also found that LaAlO3 had better oxidation resistance characteristics by a factor of six than SiO2 at 800degreesC. Next, MFMIS diodes composed of SrBi2Ta2O9 and LaAlO3 were fabricated and good memory characteristics were obtained when the ratio of the MFM capacitor to the MIS capacitor was 12.