Pore morphology of low-k SiCxNy films prepared with a cyclic silazane precursor using plasma-enhanced chemical vapor deposition

Low-k SiCxNy films were prepared using radio-frequency plasma-enhanced chemical vapor deposition (PECVD), with only 1,3,5-trimethyl-1,3,5-trivinylcyclotrisilazane (VSZ) as the precursor; VSZ has cyclic Si-N-Si linkages and three pendent vinyl groups. At lower PECVD temperatures, SiCxNy films possess relatively low film densities, indicating the existence of a loose structure or voids within the cross-linked matrix structure. The pore morphology of SiCxNy films deposited at distinct temperatures were examined using grazing-incidence small-angle X-ray scattering, while the chemical bondings and structural information were analyzed using Fourier-transform infrared spectroscopy. At 100 °C, SiCxNy films without porogen displaying 4.9 nm pores and a mean pore spacing of 30.1 nm generated low-density films because Si-(CH2)n-Si and/or Si-(CH2)n-CH3 could be incorporated free volume into the N-Si-C cross-linked structure under plasma deposition. At 300 °C, the N-Si-C cross-linked structure and the some organic phase were disrupted and transformed into a denser structure, reducing pore size (3.5 nm) and losing pore correlation. Thus, low deposition temperatures facilitate the formation of large pores and the ordering of the pores. Post annealing converted the 100 and 300 °C as-deposited SiCxNy films into loose and dense structures, respectively, and maintained slightly reduced pore size and pore correlation in the annealed films.