Physicochemical characterization by means of IR absorption spectroscopy of Si 3N 4 thin films obtained by chemical vapour deposition assisted by in situ electrical disharge

Abstract

An original process has been developed enabling the fabrication by chemical vapour deposition of insulating (Si 3N 4, SiO 2,…) thin films, by means of in situ activation of the reactions at low temperature ( T < 400°C) and under low pressure ( P = 1−2 Torr ). The activation was performed by a d.c. electrical discharge. The substrate was not used as an electrode, and was placed parallel to the electric field. During the deposition process, several activation mechanisms can interfere, for example UV activation, photo-sensibilization, and direct activation by impacts (as is observed during thermal activation), and various thin films can be obtained. The compositions of layers having various widths and obtained under various conditions were analysed using Fourier transform IR absorption spectroscopy. Typical results obtained from IR spectroscopy are presented. They show how the deposition technique presented here is interesting and how IR spectroscopy can be used as a non-destructive interactive analysis technique during the manufacture of insulating thin films.