Patent ID: 7521156

Claim:
A photo mask comprising: a substrate comprising a transparent material that is transparent to an exposure light; and a light-shielding layer pattern on a front surface of said substrate, said light-shielding layer pattern having a target critical dimension, and said light-shielding layer pattern comprising light-shielding elements that define transmission sites therebetween and at which sites said substrate is exposed, the transmission sites have critical dimensions corresponding to the distances between adjacent ones of the elements of said light-shielding layer patterns, respectively, and each of the transmission sites have a critical dimension that differs from that of at least one other of the transmission sites such that the critical dimensions of the transmission sites vary amongst one another, and wherein the transparent substrate has at the front surface thereof impurities at all of the transmission sites, the impurities constituting low transmissivity regions extending across said transmission sites and having a transmissivity with respect to said exposure light that is less than that of said transparent material of the substrate, and the concentration of the impurities being uniform across all of the transmission sites whose critical dimensions vary amongst each other and correlate with the critical dimensions of the transmission sites.