Method of forming porous film and material for porous film

DETAILED DESCRIPTION In view of the aforementioned conventional problems, an object of the invention is providing a method, as simple as the conventional SOG process, of forming a porous film in a short period of time at a low temperature under atmospheric pressure, in which a material for the porous film can be prevented from degrading with time, and in which the diameter of a pore in the porous film can be minimized sufficiently for integration in an LSI so as to decrease the dielectric constant of the porous film.
In order to achieve the object, the first method of forming a porous film of this invention comprises the steps of forming a coating film by applying, on a substrate, an organic acid containing solution obtained by adding an organic acid having an alkyl group to a solution including silanol condensate particles; and forming a porous film from the coating film by conducting a heat treatment on the coating film.
In the first method of forming a porous film, the organic acid having an alkyl group is preferably propionic acid, acetic acid, butyric acid, isobutyric acid, isovaleric acid, valeric acid, 2-ethyl-n-butyric acid or trimethylacetic acid.
The second method of forming a porous film of this invention comprises the steps of forming a coating film by applying, on a substrate, an organic acid containing solution obtained by adding an organic acid having halogen to a solution including silanol condensate particles; and forming a porous film from the coating film by conducting a heat treatment on the coating film.
In the second method of forming a porous film, the organic acid having halogen is preferably chloroacetic acid, dichloroacetic acid, trichloroacetic acid, fluoroacetic acid, difluoroacetic acid or trifluoroacetic acid.
The third method of forming a porous film of this invention comprises the steps of forming a coating film by applying, on a substrate, an organic acid containing solution obtained by adding an organic acid having a hydroxyl group to a solution including silanol condensate particles; and forming a porous film from the coating film by conducting a heat treatment on the coating film