Ion-assisted low-temperature oxidation for fabrication of strained Si_1-xGe_xand Si_1-x-yGe_xC_yMOS capacitors

Abstract

Ion-assisted oxidation has been carried out at a substrate temperature of 150 • C 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 x C 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.