The interaction between low-k organosilicate glass (OSG) and photoresist removal is investigated. O-2 plasma ashing and chemical wet stripper are commonly performed to remove photoresist (PR) in integrated circuit fabrication. However, O-2 plasma or wet stripper will attack function groups and cause Si-OH group formation in OSG film during PR removal processing. The Si-OH groups often lead to moisture uptake and consequently dielectric degradation will occur in OSG film. Trimethylchlorosilane (TMCS) treatment can negate the damage in the OSG film after the PR removal process. In addition, chemical TMCS can react with Si-OH groups and reduces moisture uptake so that the dielectric characteristic of OSG can be maintained. Hence, TMCS treatment is a promising method for photoresist removal.