Theoretical study on silicon-nitride film growth: Ab initio molecular orbital calculations

The growth mechanism of SiN films in the chemical vapor deposition process was theoretically investigated using ab initio molecular orbital methods. A reactive intermediate SiH2 (or SiCl2) is produced by the thermal decomposition of SiH4 (or SiH2Cl2). The intermediate inserts into the N—H bond of NH3 to form H3Si—NH2 (or HCl2Si—NH2). From the Si atom of the insertion product, H2 (or HCl) is eliminated and a silylene-like reaction site (—Si—H) is created again. Such processes generate various kinds of SiN particles. On the surface of SiN film, SiH2 (or SiCl2) insertion and H2 (or HCl) elimination seem to occur repeatedly, which leads to the SiN film growth. Thus, the chemical features of SiH2 and SiCl2 may explain the difference of the film-growth mechanisms between the mixtures of SiH4+NH3 and SiH2Cl2+NH3.