Bulk and interface properties of low-temperature silicon nitride films deposited by remote plasma enhanced chemical vapor deposition

Abstract

Hydrogenated silicon nitride (a-SiNx: H) films were deposited at temperatures ranging from 50 to 300 degreesC with remote plasma enhanced chemical vapor deposition (RPECVD) from NH3 and SiH4. The effect of the operating variables, such as deposition temperature and especially the partial pressure ratio of reactant (R = NH3/SiH4) on the properties of the SiNx : H films and the Si/SiNx: H interface was investigated. The NH* radical was dominantly observed and the deposition rate was proportional to the NH* radical concentration. The density of highly energetic N*(2) radicals increased in the high plasma power regime in which the film surface was roughened, but they promote surface reactions even at low temperature. The refractive index was more closely related to the film stoichiometry than film density. The interface trap density is related to the amount of silicon intermediate species and Si-NH bonds at the Si/SiNx: H interface and it can be minimized by reducing the intermediate Si species and Si-NH bonding state. The films showed a midgap interface trap density of 2 x 10(11) - 2 x 10(12) cm(-2). (C) 2001 Kluwer Academic Publishers.