Ion-assisted low-temperature oxidation for fabrication of strained Si_(1-x)Ge_x and Si_(1-x-y)Ge_xC_y MOS capacitors

摘要

Ion-assisted oxidation has been carried out at a substrate temperature of 150 ℃ for fabrication of metal-oxide-semiconductor capacitors using fully strained Si_(1-x)Ge_x (x = 0.2 and 0.26) and partially strained Si_(1-x-y)Ge_xC_y (Ge:C = 20: 1 and 40: 1) films. The oxide thickness is designed to consume a part of the Si-cap layer, leading to the formation of a valence band quantum well for confining the carriers away from the Si-SiO_2 interface. The fixed oxide charge density and mid-gap interface trap density are found to be higher for the sample containing higher Ge and C concentration. The presence of hole-trapping centres is observed for all the samples. However, a decrease in the hole trap density is observed either with the reduction of Ge content or with the increase of carbon fraction in the film.