BOROPHOSPHOSILICATE GLASS CRYSTAL INDUCTION AND SUPPRESSION

Grapelike crystalline cluster defects with no specific shapes were induced in borophosphosilicate glass (BPSG) deposited in a low-pressure chemical vapor deposition tube following cooling of the film to room temperature. The crystal defects were induced by exposing the film for about 3 min to high, controlled humidity (80%-90%) and a temperature of 30 +/- 2-degrees-C. The film was then fused for 15 min in a 900-degrees-C furnace at four different atmospheres: N2, O2, 1:1 O2/N2, or steam (3 min)/N2 (12 min). The steam/N2 treatment was the only effective ambient to eliminate BPSG crystal defects. A chemical mechanism is proposed to explain the crystal appearance in BPSG film.