US Patent 7892955 Laser mask and crystallization method using the same

A crystallization method using a mask includes providing a substrate having a semiconductor layer; positioning a mask over the substrate, the mask having first, second and third blocks, each block having a periodic pattern including a plurality of transmitting regions and a blocking region, the periodic pattern of the first block having a first position, the periodic pattern of the second block having a second position, the periodic pattern of the third block having a third position, the first, second and third positions being different from each other; and crystallizing the semiconductor layer by irradiating a laser beam through the mask.