Vapour-deposited silicon dioxide for device applications

Abstract

Silicon dioxide layers deposited from the vapour phase at low temperatures are extensively applied in integrated circuit technology. Applications include doped oxide diffusion sources, protective layers and cross-over insulators in multilevel metallization systems. In this paper we show the feasibility of obtaining a SiO 2Si interface whose electrical characteristics closely approach those of thermally grown SiO 2Si sandwich structures. Interface state densities lying in the low 10 10 cm −2 eV −1 range have been determined from quasi-static C(V) measurements. The results of excess noise measurements made on deposited gate oxide and thermally grown gate oxide MOSFETs are in reasonable agreement with the interface state density measurements. C(V) dispersion and C(V) hysteresis measurements prior to and after exposure to 10 7 rad of 60Co γ radiation are also presented. Potential applications of low temperature vapour-deposited oxides include the silicon on insulating substrate (SOS) technology where it is generally desirable to minimize high temperature processing steps. Other applications are in the field of impurity profile determinations using the MOS capacitor method. In these applications one desires to measure the original profile without having to deal with the additional complication of the diffusion and redistribution phenomena that occur unavoidably during high temperature thermal oxide growth.