Properties of Si-rich SiNx:H films prepared by plasma-enhanced chemical vapor deposition

Abstract

Silicon-rich silicon nitride (designated SiNx:H) films, prepared by the plasma-enhanced chemical vapor deposition technique, have been studied. The films studied contain a wide range of Si contents, which are controlled by the SiH4/NH3 flowrate ratio during the deposition process. Using transmission electron microscopy, coupled with the electron diffraction technique, we have found that the as-deposited films are amorphous. Upon high-temperature (>900 °C) annealing, however, we observe silicon microcrystals in the Si-rich films. The temperature at which the microcrystals start to form decreases with increasing Si richness. Reactions of the SiNx:H film with the gate aluminum as a result of post-metallization annealing treatment (at 400 °C) have been observed, and these reactions cause a drastic reduction of the temperature required for crystallization. Charge separation and current conduction studies made on Al/SiNx:H/Si structures have revealed that electrons are the dominant current carriers for either polarity, and the conduction mechanism in the SiNx:H layer is consistent with the Poole–Frankel type of transport process for moderately Si-rich films.