Improvement of Electrical Properties and Reliability of ( Ba0.5Sr0.5 ) TiO3 Thin Films on Si Substrates by N2O Prenitridation

Abstract

The effect of silicon prenitridation on the growth of barium strontium titanate (BST) thin films prepared by rf-magnetron sputtering was investigated. The thermal nitridation of silicon using a N 2 O treatment followed by removing most of the SiO x N y sacrificial layer was employed. Only a 2 nm thick silicon oxynitride layer was left to serve as a buffer layer prior to BST sputter-deposition. The grain size of the as-deposited 30 nm BST thin film was very small, approximately 30-60 nm. The dielectric constant of the 30 nm BST thin films deposited on the Pt substrates was about 50. It was found that the equivalent oxide thickness of the BST metal-insulator-semiconductor capacitors with the prenitridation treatment was decreased by 12% and the leakage current density was lowered to 3 X 10 - 9 A/cm 2 at - 1 MV/cm as compared to the non-nitrided samples. Moreover, the reliability issues such as interface traps, flat band voltage shift, capacitance-voltage hysteresis, and breakdown characteristics were also improved by the nitridation pretreatment.