Interfacial properties of a hetero-structure YSZ/p-(1 0 0)Si prepared by magnetron sputtering

Abstract

Thin films of polycrystalline YSZ (yttria-stabilized zirconia ) of 4–500 nm in film thickness were deposited on (1 0 0)Si at 800°C by rf-magnetron sputtering of a sintered YSZ target. The sputtered YSZ thin films were evaluated as an alternate gate oxide for Si-MOSFETs. It was found that the interfacial layer of SiO x was formed between YSZ and (1 0 0)Si. The formation of the SiO x layer during the sputtering deposition of the YSZ was not predominant. The surface of the Si was chiefly oxidized during a cleaning stage and/or a pre-sputtering due to possibly residual H 2O or O 2 in a sputtering chamber. The cooling process after the deposition affected the interfacial properties. The rapid cooling in Ar ambient increased a breakdown voltage in a heterostructure Au/YSZ(1 0 0)/p-Si with evaporated gold top electrodes. A small leakage current of 5×10 −8 cm 2 at 1 V and a high breakdown voltage of 9.3 MV/cm were observed for the YSZ thin films of 7.5 nm. The resultant equivalent oxide thickness (EOT) for Si-gate oxide was 3 nm. The interfacial quality of the YSZ and SiO x seems to have a close relation to the small leakage current.