Infrared Optical Constants and Dielectric Response Functions of Silicon Nitride and Oxynitride Films

Abstract

The complex refractive indices of thick plasma-enhanced chemical vapour deposited silicon nitride and oxynitride films were determined within the infrared spectral region (4000-400 cm --1 , i.e. 2.5-25 mm) and used further to obtain their complex dielectric response functions. The imaginary part, i.e. the so-called energy-loss-function was analysed to get accurate phonon data of the amorphous layer. This way, TO-phonon frequencies, half-widths, and intensities of characteristic infrared absorptions were determined for each film. The dependence of the obtained data upon the variation of chemical/physical structure of the amorphous lattice was discussed.

Preparation and properties of clean Si3N4 surfaces

“…Fig. 1 also shows numerical simulations obtained using the matrix formulation [25] 2 for the polarized reflectance of a multilayer material, together with IR optical constants [26] for Si 3 N 4 grown on Si(1 0 0) by PECVD. To the best of our knowledge, these are the most extensive such IR data available for Si 3 N 4 .…”

“…Transmission spectra of PECVD Si 3 N 4 films show TO modes [26] at 805 and 936 cm À1 corresponding to Si-N stretching vibrations for N bonded to three and to two Si atoms, respectively. The presence of both species in PECVD Si 3 N 4 is responsible for the broadening seen in the TO region of the simulation, Fig.…”

“…The high Si-H frequency is consistent with a stoichiometric Si 3 N 4 film [36] in which (-N-) 3 Si-H is the dominant silane species. However, a simple interpretation is complicated by the fact that the mode frequency for (-N-) 3 Si-H in an oxygen-free film is reported [26,36] to be 2170 cm À1 , significantly lower than the present value of 2200 cm À1 . This could indicate that the Si-H bonds are associated with a small level of O impurity (in the form of a species such as (-N-) 2 (-O-)Si-H) where the higher electronegativity of O versus N would give rise to a higher Si-H frequency [36].…”

“…Alternatively, the H could be bound at Si sites at the Si 3 N 4 surface or at the buried interface with the Si IRE, where higher concentrations of O are expected. The N-H frequency, on the other hand, is characteristic of NH in oxygen-free Si 3 N 4 [26]. Adding O to the film shifts this mode to higher values [26], and -NH 2 in Si 3 N 4 would exhibit a stretching mode at $3460 cm À1 [37].…”

Detection of Silicon Nitride Particles in Extreme Carbon Stars

“…However, these investigations are mainly based on thin films of bulk (nonparticulate) amorphous Si 3 N 4 (e.g., Taft 1971;Yin & Smith 1990;Klanjsek Gunde & Macek 2001). Therefore, the obtained spectra are not directly comparable to absorption spectra of small particles.…”