Realizing Ultrauniform Films at Wafer Scale through the Magnetron Sputtering Method

Thickness is a crucial parameter that significantly influences the optical, piezoelectric, and magnetoelectric properties of films. Reducing the film's thickness nonuniformity at wafer scale is quite important for industrial manufacturing but difficult and challenging. Conventionally, the complementary metal-oxide-semiconductor transistor (CMOS)-compatible magnetron sputtering (MS) method employs planar targets, which often leads to an unsatisfactory thickness distribution, i.e., thick in the center and thin at the edges. To address this issue, a concave target is proposed based on the theoretical thickness distribution model and is experimentally manufactured to optimize the thickness nonuniformity of magnetron-sputtered films. Additionally, the influences of target size and target-substrate distance are also investigated. Our results demonstrate that using a concave target with a large radius is effective for improving the thickness uniformity. For instance, ultrauniform Mo films are deposited onto a 2-in. Si/SiO2 wafer, exhibiting a notably low thickness nonuniformity of 0.38%. Our results provide theoretical guidance and the experimental prototype for the large-scale preparation of ultrauniform films. Moreover, these findings could be applied to other materials.