Abstract: Thin film silica was fabricated by using sol gel process into inorganic ceramic material through hydrolysis and condensation reaction. This process aims to form silica insoles that provide a strong tissue structure that can be applied as thin films on membrane fabrication. This process was conducted by mixing tetraethyl orthosilicate (TEOS) as the main precursor, ethanol and H2O as solvent and citric acid as catalyst. Concentration of citric acid to use is 0,001 % and 0,005 %. This process is carried out for 3 hours at 0 ° C. Sols are dried in oven and calcined at various temperatures (200, 250 and 400°C) in order to know the carbon chain formed in the silica matrix. The effect of carbon in silica structure was then analyzed by FTIR and TGA. The result of wavelength indicated by Infra Red is known that the optimum catalyst is used as the citric acid concentration of 0.001 %, because at that concentration the silanol produced was small, hence, it may create mesopori size of silica matrix and the resulting pH 6 that is effectively applied as membrane coatings. The TGA results show that the optimum calcination temperature is at 400°C due to good thermal stability, besides carbon bond also still exist in the silica matrix. Keywords: Silica thin film, sol gel, precursor, calcination, catalist.