Effect of oxidation on the chemical bonding structure of PECVD SiNx thin films

Abstract

This study investigated the effect of oxidation on the chemical bonding structures of silicon nitride thin films synthesized by a low-temperature plasma-enhanced chemical vapor deposition ͑PECVD͒ method. These films were heat treated to different temperatures up to 1373 K. The bonding structures were studied by means of x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. It was found that the amorphous PECVD SiN x films were subjected to oxidation in air at elevated temperatures. The oxidation caused the formation of crystalline silicon dioxide within the matrix of amorphous silicon nitride, conforming to the "random mixing" model. The crystalline silicon dioxide formed is believed to be stoichiometric SiO 2 , whereas the remaining matrix is believed to be a nonstoichiometric silicon oxynitride with a structure conforming to the "random bonding" model.

Oxidation of PECVD SiNx thin films

“…It ought to be pointed out that further detailed XPS analysis indicates that amorphous SiN x in the oxidized film actually contains certain amount of oxygen, i.e. it is in fact silicon oxynitride, expressed as SiN 1−x O x [26], whereas, the crystalline SiO 2 is pure SiO 2 . The identification of the silicon oxynitride is consistent with previous studies [27].…”

“…5 shows the FTIR measurements of the four films. The FTIR spectra showed absorbance peaks corresponding to the N-H bond, Si-O bond and Si-N bond [3,25,26]. It is seen that the as-deposited film contained both N-H and Si-N bonds.…”

Process condition dependence of mechanical and physical properties of silicon nitride thin films

“…The films used in this study have previously been shown to contain no physical porosity. 21 In this regard, the large variation in can only be attributed to the large variations in atomic compositions of the films deposited under different conditions. The variations in atomic composition also affect the density of the films, as discussed.…”

“…The films deposited are found to be perfectly dense without any sign of pinholes or physical porosity. 21 In this regard, the large variation in density is attributed to significant variations in the chemical and molecular structure of the films, i.e., the films deposited at high and low temperatures are chemically different. Decreasing the deposition temperature decreases the completeness of the film deposition reactions.…”

Crystallization and compositional changes in amorphous PECVD SiN x thin films

“…Recent studies have shown that exposure to high temperatures causes changes in the chemical composition, atomic bonding structure and film morphology of PECVD SiN x films [8][9][10][11] . In particular, crystallization is observed during high temperature heat treatment in air.…”