Abstract
Abstract In this work, the electrical characteristics of Al/BST/Si (P-type) (MIS) capacitors and n-channel metal gate metal-oxide-semiconductor field effect transistors (MOSFET) with (BaxSr1-x)TiO3 (BST) gate dielectric are investigated. The BST thin films are deposited by magnetron control RF sputtering. The perovskite phase was confirmed by X-Ray Diffraction spectra. The dielectric constant of 96nm thick BST thin film is around 47 at 1MHz and 77 at 100Hz. The I-V and C-V characteristics of MIS capacitors are discussed. The conduction current mechanism of BST films at different temperatures is studied. For MIS structure, Ohmic conduction is dominant at high temperature under low electrical field, when the device is negative biased (operated in accumulation region). The EC-EF is 0.2eV, the mobility in BST thin film is 2.28×10-5 cm2/V-sec, and the thermal equilibrium concentration of free electrons in BST thin film is 1.57×1017 cm-3 extracted from ohmic conduction. Schottky emission is observed at high temperature under high electrical field. At higher electrical field (>150kV/cm) and with the Si/Al electrode positively biased, the Al/BST forms a Schottky barrier with a barrier height of 0.63eV in the temperature range from 340 to 430 K. The IDS-VDS and IDS–VGS characteristics are measured from MOSFET with BST gate dielectric. The electron mobility obtained from gm versus VG plot was about 187 cm2/V·s. The subthreshold swing was 125.9 mV/dec. The interface trap density and fixed oxide charge measured from Vt and St are 2.091×1012cm-2, 3.3×1012cm-2ev-1, respectively. Comparison with conventional MOSFETs with SiO2 gate oxide was made. It shows that the surface properties of BST transistors are worse than SiO2 transistors. For BST transistors, there are still many places for improvement in the future.