The present disclosure provides an electrostatic chuck for holding a wafer. The electrostatic chuck includes at least one dielectric layer, an electrode layer coupled to the dielectric layer, and a chuck base. The chuck base includes a plurality of lock holes. The dielectric layer and the electrode layer are disposed on the chuck base. Each of the lock holes of the chuck base includes a first portion and a second portion connected to the first portion. The first portion has a first opening on a bottom surface of the chuck base. The second portion has a second opening on the bottom surface of the chuck base. A width of the second opening of the second portion is smaller than a width of the first opening of the first portion.