Patent ID: 8730475

Claim:
A method of aligning a substrate, the method comprising: sequentially identifying a first alignment mark, a second alignment mark, a third alignment mark and a fourth alignment mark in a first shot region of the substrate, the first alignment mark having a first brightness, the second alignment mark having a second brightness lower than the first brightness, the third alignment mark having a third brightness lower than the second brightness and the fourth alignment mark having a fourth brightness lower than the third brightness; primarily aligning the substrate using a primarily identified alignment mark of the first alignment mark, the second alignment mark, the third alignment mark and the fourth alignment mark; sequentially identifying a used alignment mark, which is used for primarily aligning the substrate, of the first alignment mark, the second alignment mark, the third alignment mark and the fourth alignment mark in a second shot region of the substrate; sequentially identifying the rest of the alignment marks in the second shot region, which are not used for primarily aligning the substrate, in order of the brightness when the used alignment mark during primarily aligning the substrate is not identified; secondarily aligning the substrate using a primarily identified alignment mark of the rest of the alignment marks in the second shot region; sequentially identifying a used alignment mark, which is used for secondarily aligning the substrate, of the first alignment mark, the second alignment mark, the third alignment mark and the fourth alignment mark in a third shot region of the substrate; sequentially identifying the rest of the alignment marks in the third shot region, which are not used for secondarily aligning the substrate, in order of the brightness when the used alignment mark during secondarily aligning the substrate is not identified; and tertiarily aligning the substrate using a primarily identified alignment mark of the rest of the alignment marks in the third shot region.