METHOD FOR PRODUCING PHOTOMASK BLANKS Russian patent published in 2007 - IPC H01L21/302 

FIELD: electronic industry.

SUBSTANCE: proposed method for producing photomask blanks involves two-stage polishing; first stage includes pre-polishing using perforated polishing canvas based on synthetic fibers, 8- 10 μm in diameters, at cubic density of 0.25 g/cm³; perforated holes are staggered; perforated-to-non-perforated area ratio being 0.08 0.09: 1, with ultrasonic action at frequency of 20 - 50 kHz for 30 - 50 minutes, temperature of 20 - 40 °C, and glass removal speed of 0.6 - 1.0 μm/min, whereupon glass removal is checked up and wafer is washed out in three-step ultrasonic line using surface active materials; during second stage wafer is subjected to finishing polishing by removing 10 - 12 μm of glass for 10- 15 minutes using softer polishing canvas.

EFFECT: enhanced surface quality of glass wafers for photomasks.

1 cl, 1 tbl