A method for wafer alignment includes the following steps. First, a wafer including a first material layer and a second material layer on the top of the first material layer is provided, wherein the first material layer includes a first alignment mark. Then, the wafer is aligned in an exposure tool. After that, the second material layer is patterned to form a second alignment mark. Finally, an offset distance between the first alignment mark and the second alignment mark is measured in the exposure tool.