Patent ID: 7377984

Claim:
A method of cleaning a photomask, comprising: (a′) conducting a first cleaning on the photomask using an aqueous solution containing hydrogen peroxide and an acid; (b′) conducting a first heat treatment by heating the photomask in a furnace or oven having a gaseous atmosphere for activating ions from the acid remaining on the photomask after completing step (a′); (c′) conducting a rinsing on the photomask using ultrapure water for removing the activated acid ions; (d′) conducting a second cleaning on the photomask after completing step (c′) using an aqueous solution comprising ammonia, hydrogen peroxide, and hydrogen water; (e′) conducting a second heat treatment on the photomask in a furnace or oven having a gaseous atmosphere for activating ions from the ammonia remaining on the photomask after completing step (d′); and (f′) conducting a rinsing on the photomask using ultrapure water for removing the activated ammonia ions from step (e′).