The thermodynamic modeling of the deposition of the condensed phase of a complex composition has been performed in the Si-C-N-O-H system in the broad temperature range of 300–1300 K under total pressure Ptotal0 = 6−7×10−2 Torr and residual air pressure in reactor Pres = 5 × 10−3 Torr using the initial gas mixtures of organosilicon compound, hexamethyldisilazane (HMDS), with nitrogen, oxygen, air mixture (O2 + 4N2), and a variable mixture of oxygen with nitrogen (O2 + xN2). The temperature boundaries of multiphase ranges, where one can anticipate the deposition of silicon oxycarbonitride, silicon oxycarbides, and silicon oxynitride, have been determined.