Impact of film structure on damage to low-k SiOCH film during plasma exposure

We investigated the resistance of a low-k SiOCH film structure to plasma-irradiation damage by comparing films deposited by neutral-beam enhanced chemical-vapour-deposition (NBECVD) and conventional plasma CVD techniques to clarify the degradation mechanism of the dielectric constant in low dielectric SiOCH film during plasma etching. We found that the durability of a low-k SiOCH film structure to plasma irradiation strongly depended on the kind of Si-O structure the film had. In particular, a linear Si-O structure was less affected by plasma exposure than were network/cage Si-O structures because of the small amount of stress in the O-Si-O structure. In addition, this linear Si-O structure helped to reduce the number of methyl groups removed from the film by plasma irradiation, which preserved the dielectric constant. Since the NBECVD technique can generate a low-k SiOCH film with more linear Si-O structures than conventional plasma CVD, a film made through this technique has very strong plasma durability.