Patent ID: 7474468

Claim:
A method of forming a pattern, comprising: irradiating a beam onto a patterned reflective mask; and irradiating the beam reflected from the patterned reflective mask onto a wafer through an off-axis projection optics to form a pattern corresponding to the patterned reflective mask, wherein the off-axis projection optics comprising first and second mirrors positioned off-axis and sharing a confocal point that are arranged to reduce linear astigmatism, when a distance between an object plane and the first mirror is l 1 , an incident angle of light coming from the object plane to the first mirror is i 1 , a distance between the first mirror and the confocal point is l 1 ′, a distance between the confocal point and the second mirror is l 2 , an incident angle of light coming from the first mirror to the second mirror is i 2 , and a distance between the second mirror and an image plane is l 2 ′, the arrangement of the first and second mirrors satisfy the following l 1 ′ + l 1 l 1 ⁢ tan ⁢ ⁢ i 1 = l 2 ′ + l 2 l 2 ⁢ tan ⁢ ⁢ i 2 .