The dielectric properties of organic-porous silica films deteriorate after photoresist removal processing. O-2 plasma ashing has been commonly used to remove photoresist. Nevertheless, the O-2 plasma will destroy the functional groups and induce moisture uptake in porous silica films. In this study, trimethylchlorosilane (TMCS) is used to repair the damage to porous silica caused by the O-2 plasma ashing process. The leakage current and dielectric constant will decrease significantly after the TMCS treatment is applied to damaged porous silica. These experimental results show that the TMCS treatment is a promising technique to repair the damage to porous silica during photoresist removal processing.