Repair of plasma-damaged p-SiOCH dielectric films in supercritical CO2

The silylation of plasma-damaged p-SiOCH low-k dielectric films was investigated with trimethychlorosilane (TMCS), hexamethyldisilazane (HMDS) and dimethyldichlorosilane (DMDCS) dissolved in supercritical CO2 (scCO2) and the effect of thermal pre-treatment on the repair performance was also studied. The surface hydrophobicity was rapidly recovered by silylation and the order of recovery efficiency was HMDS (85.4°) > DMDCS (83.4°) > TMCS (75.0°). The FTIR analyses revealed that the restoration to the original state was not achieved over various reaction conditions (up to 31 MPa, 85 °C, and 3 h reaction time). After pre-treatment in a vacuum cell at 250 °C, the Si-O-Si peak intensity increased slightly, and the surface hydrophobicity was partially recovered to 54.4° due to the removal of physically adsorbed H2O molecules as well as some extent of dehydration of neighboring surface silanol groups. The hydrophobicity increased to 84.4° after subsequent treatment with HMDS in scCO2. From DSIMS, the carbon concentration did not increase in bulk region after silylation of thermally pre-treated low-k films.