Patent ID: 9620458
Date: 2017-04-11
CPC Classifications: G02B,G03F,H01L

Claim:
1. A method for fabricating a photolithography alignment mark structure, comprising: providing a semiconductor substrate; forming a first grating, a second grating, a third grating and a fourth grating in the substrate; forming a photoresist layer on a surface of the substrate; obtaining a first alignment center along a first direction and a second alignment center along a second direction based on the first grating and the fourth grating, respectively, by using grating diffraction; providing a mask plate having a fifth grating pattern and a sixth grating pattern on the mask plate; aligning the mask plate with the substrate by using the first alignment center as an alignment center along the first direction and the second alignment center as an alignment center along the second direction, wherein reticles of the second grating are interlaced with reticles of the fifth grating pattern, and the fifth grating pattern has an offset of a first distance along the first direction with respect to the second grating; and reticles of the third grating are interlaced with reticles of the sixth grating pattern, and the sixth grating pattern has an offset of the first distance along a reverse direction of the first direction with respect to the third grating; reproducing the fifth grating pattern and the sixth grating pattern in the photoresist layer on the substrate through an exposure process; and forming a fifth grating and a sixth grating on the surface of the substrate by removing a portion of photoresist layer.