Wafer structure and method for fabricating the same

A wafer structure and a method for fabricating the same are provided. First, a wafer having a pad and a first protection layer is provided. The first protection layer covers the wafer and has a first opening exposing part of the pad. Next, a second protection layer with a second opening is formed on the first protection layer. Part of the pad and the first protection layer is exposed from the second opening that. The second opening is larger than the first one, and the edge of these two openings construct a step structure. After that, an adhesion layer is formed on the pad, the step structure and the second protection layer. Then, a photo-resist layer with a third opening is formed on the adhesion layer. The third opening is located over the pad and exposes part of the adhesion layer. Following that, a barrier layer is electroplated onto the exposure part of the adhesion layer. Further, a wetting layer is formed on the barrier layer. Afterward, the photo-resist layer and part of the adhesion layer that expose