Patent ID: 7732104
Filing Date: 2010-06-08
Classification: B23K,G02B,G03F

Abstract:
1. A method of reducing periodic structure formed in a photomask material during a laser ablation process, the method comprising: converting incident linearly polarized laser light pulsed from a laser into circularly or eliptically polarized laser light; altering the polarization direction of the linearly polarized laser light that is converted to the circularly or eliptically polarized laser light and is incident on the photomask material during each pulse of the laser; irradiating the photomask material with the focused incident circularly or eliptically polarized laser light; averaging a plurality of polarization directions effected during the ablation process; and wherein the polarizing and averaging are implemented by inserting a quarter wave plate into an optical path of the linear pulsed laser light to produce the circularly or eliptically polarized light during the laser ablation process.