Patent ID: 7232769

Claim:
A method of forming an amorphous silica-based coating film with a low dielectric constant having a high film strength and excellent hydrophobic property and capable of ensuring smoothness of a surface coated therewith on a substrate comprising the steps of: (a) preparing a liquid composition containing: 1) a silicon compound obtained by hydrolyzing tetraalkyl ortho silicate (TAOS) and alkoxysilane (AS) expressed by general formula (I) in the presence of tetraalkyl ammonium hydroxide (TAAOH) purified to remove impurities comprising compounds of alkali metal elements and halogen group elements; and 2) said tetraalkyl ammonium hydroxide (TAAOH); and wherein the general formula is: X n Si(OR) 4-n (I) wherein X indicates a hydrogen atom, a fluorine atom, or an alkyl group, a fluorine-substituted alkyl group, an aryl group or a vinyl group each having 1 to 8 carbon atoms; R indicates a hydrogen atom, or an alkyl group, an aryl group or a vinyl group each having 1 to 8 carbon atoms; and n is an integral number from 1 to 3, (b) applying the liquid composition on a substrate; (c) heating the substrate at a temperature in a range from 80 to 350° C.; and (d) curing the substrate at a temperature in a range from 350 to 450° C.