Patent ID: 6537623
Filing Date: 2003-03-25
Classification: C23C,G02B

Abstract:
A method of making a high quality optical silica film coated on a substrate with reduced optical absorbance, comprising:(a) subjecting said substrate to a gaseous mixture of silane and nitrous oxide, to deposit said silica film on said substrate in accordance with the reaction SiH4(g)+2N2O(g)â†’SiO2+2N2(g)+2H2(g) (b) subjecting the silica film coated on the substrate to a temperature of about 600Â° to about 1000Â° C. under nitrogen, under an inert atmosphere, or under vacuum; (c) increasing the temperature to a maximum temperature of at most 1350Â° C.; (d) exposing the silica film to a reactive atmosphere comprising oxygen atoms and hydrogen atoms for at least 30 minutes by replacing the nitrogen, inert atmosphere, or vacuum by the reactive atmosphere to chemically remove unwanted compounds; (e) removing the silica film from the reactive atmosphere by replacing the reactive atmosphere with nitrogen, an inert atmosphere, or vacuum; (f) decreasing the temperature from the maximum temperature to about 600Â° to about 1000Â° C.; and (g) recovering the silica film coated on the substrate.