Suppression of surface crystallization on borosilicate glass using RF plasma treatment

Surface crystallization on a commercial grade borosilicate glass wafer, Borofloat^® 33, is effectively prevented against 3h of thermal reflow process at 850 °C. Surface plasma treatment with three different reactive gases, CF₄, SF₆, and Cl₂, has been performed prior to the annealing. The effect of plasma treatment on surface ion concentration and nucleation of cristobalite were examined through optical microscope and x-ray photoemission spectroscopy. The dominant cause that suppresses crystallization was verified to be the increase of surface ion concentration of alumina during the plasma treatment. Both CF₄ and SF6 treatment of no less than 30 s showed significant efficacy in suppressing crystallization by a factor of more than 112. Average surface roughness and the optical transparency were also enhanced by a factor of 15 and 3, respectively, compared to untreated sample.