Surface-sensitive multiple internal reflection spectroscopy as a tool to study surface mechanisms in CVD: the example of UV photodeposition of silicon dioxide and silicon nitride

Multiple internal reflection-absorption spectroscopy is used here in situ in a low pressure CVD reactor, in order to demonstrate its potential as a surface analysis tool with a sensitivity well below monolayer coverages in many growth and deposition configurations. Two examples of its capacity to provide evidence for new surface processes are given in the particular case of photodeposition of silicon dioxide and silicon nitride: (i) identification of the molecular configuration associated to the photochemisorbed silane site on the Si₃N₄ photodeposition front in the SiH₄/NH₃ system, in a case where its infrared signature is buried in a large contribution from bulk species; (ii) evidence for the oxidization of silicon hydride and dihydride species by photoexcited N₂O in the UVCVD of SiO₂ in the SiH₄/N₂O precursor system. Such a reaction could be expected to occur from standard chemical knowledge, but deposited films analyzed ex situ did not offer any evidence for it in the form of water and silanol groups incorporated into the films.