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 3 h 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.