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

Abstract

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.