The interaction between low dielectric constant (low-k) hybrid organic siloxane polymer (HOSP) and O-2 plasma ashing has been investigated. O-2 plasma ashing is commonly performed to remove the photoresist (PR) during integrated circuit fabrication. However, dielectric loss usually occurs in the HOSP films during the PR removal process. In order to eliminate dielectric loss originating from an O-2 plasma attack, hexamethyldisilazane (HMDS) treatment is proposed to repair the damage in the HOSP film. HMDS can react with Si-OH bonds and reduce moisture uptake. Moreover, the leakage current and the dielectric constant is decreased significantly when damaged HOSP film undergoes HMDS treatment. For this reason, HMDS treatment is a promising method to apply to the photoresist removal.