Macro porous silicon can be made by substrate material which is P structure doped with single polished surface, crystal orientation<111>, specific resistance is 8-13Ωcm, configured with 40% HF and absolute ethyl alcohol by proportion 1:1 after 30 minutes’ electrochemical corrosion in the double groove. When the corrosion electricity density is 20、30 and 40mA/cm2, the porosity of macro porous silicon is 50.0%、63.9.7% and 66.7% which increases with the electricity density. The surface of macro porous silicon appears obvious macro porous structure. The spread of macro porous is uniform, dimension is 1～2um, the pore wall is thick. WO3 sputtered on the surface of macro porous silicon under corrosion electricity density 40mA/cm2 do not cover the pore, instead it is filled in the side wall of pore and becomes continuous thin film.
The thickness of macro porous silicon enlarges with the rising of corrosion electricity density. Porous silicon has a certain sensitivity toward NH3 and NO2 under room temperature. Macro porous silicon tungsten oxide thin film has similar sensitivity toward NO2 of volume fraction 200×10-9 and NH3 of volume fraction 20×10-6 under either high temperature or low temperature.