Method for forming fluorine-doped glass having low concentrations of free fluorine

Abstract

This invention is a method for forming fluorine-doped silicate glass having low concentrations of free fluorine atoms. A first embodiment of the invention provides simultaneous deposition of the fluorine-doped glass and scavenging of free fluorine atoms from the surface of the depositing material. A silicon-containing compound, an oxidizer, a fluorine containing compound and a hydrogen-containing gas are introduced into a plasma chemical vapor deposition chamber. A fluorine-doped glass layer having low concentrations of free fluorine atoms deposits. A second embodiment of the invention provides for scavenging of free fluorine atoms from an already-deposited fluorine-doped glass layer by annealing the layer in a forming gas containing hydrogen. The hydrogen gas diffuses into the deposited film and reacts with free fluorine atoms. The hydrogen fluoride so formed migrates through the matrix to the surface of the deposited film, where it is released into the ambient. A third embodiment of the invention provides a method for decreasing the amount of free fluorine atoms in an already-deposited fluorine-doped glass layer by depositing a capping layer over the glass layer and annealing the resulting stack. Many of the free fluorine atoms in the layer migrate and react with dangling silicon bonds within the layer. A subsequent anneal with the capping layer removed and in the presence of a forming gas containing hydrogen, as heretofore described, further lowers the concentration of free fluorine atoms.

Dependencies are inferred from the claim text.