Abstract: A photoresist mask removing method for effectively removing polymers produced as by-products during etching of a metal layer includes processing the polymers prior to removal to facilitate removal thereof. To remove the photoresist mask remaining on a semiconductor substrate after the metal layer is dry-etched in an etching chamber, the semiconductor substrate is preferably conveyed from the etching chamber to an ashing chamber without vacuum break. The semiconductor substrate is pretreated by supplying N2 gas into the ashing chamber under the vacuum state without applying RF power to the ashing chamber to blow the N2 gas on the semiconductor substrate heated up to a predetermined temperature. This pretreatment modifies the polymer by-products to facilitate removal thereof during ashing. The photoresist mask and the polymer by-products are removed by ashing in the ashing chamber.