maximize the yield of chips formed close to the edge of the wafer in this step a support ring 104 at the edge of the wafer 100 is formed and the width of the support ring 104 is the difference between the radius of the wafer 100 and the radius of the recessed space 130 in this step the designed thickness of the thin wafer 100 can be adjusted by the depth of the recessed space 130 the support ring 104 and the thinned packaging layer 120 provide a mechanical support for the thinned wafer 100 thus the thinned wafer is not easy to crack in one embodiment the radius of the recessed space 130 is smaller than the radius of the first packaging layer 120 in order to further maintain the mechanical strength of the thinned wafer 100 so that a portion of the first packaging layer 120 can be partially overlapped with a portion of the support ring 104 in examples of the present disclosure an optional metal layer 140 a is deposited at the bottom surface of the wafer 100 in the recessed space 130 for an ohmic contact and used as a barrier for the metal seed layer 140 fig5 to diffuse into the semiconductor wafer 100 as shown in fig5.