A method of passivating silicon-oxide based low-k materials using a supercritical carbon dioxide passivating solution comprising a silylating agent is disclosed. The silylating agent is preferably an organosilicon compound comprising organo-groups with five carbon atoms such as hexamethyldisilazane (HMDS) and chlorotrimethylsilane (TMCS) and combinations thereof. The silicon oxide-based low-k material, in accordance with embodiments of the invention, is maintained at temperatures in a range of 40 to 200 degrees Celsius, and preferably at a temperature of about 150 degrees Celsius, and at pressures in a range of 1,070 to 9,000 psi, and preferably at a pressure of about 3,000 psi, while being exposed to the supercritical passivating solution. In accordance with further embodiments of the invention, a silicon oxide-based low-k material is simultaneously cleaned and passivated using a supercritical carbon dioxide cleaning solution.