Patent ID: 7807267

Claim:
A method for modifying a porous film mainly having Si—O bonds to obtain a modified porous film having a relative permittivity of 2.6 or less, the method comprising: conducting a thermal treatment at a temperature from 100° C. to 600° C. to the porous film without using a metal catalyst, wherein in the thermal treatment, an outer surface of the porous film and an inside surface of a pore of the porous film are brought into contact with an organic silicon compound including one or more Si—O—Si bond unit and two or more Si-A bond units (wherein A represents H, OH, OC e H 2e+1 or a halogen atom and may be the same or different within a single molecule; and e is an integer between 1 and 6), the organic silicon compound is a cyclic siloxane and the molecular weight of the cyclic siloxane is not more than 900, and wherein the contacting is carried out in a gas phase.