A semiconductor chip comprises a metal pad exposed by an opening in a passivation layer, wherein the metal pad has a testing area and a bond area. During a step of testing, a testing probe contacts with the testing area for electrical testing. After the step of testing, a polymer layer is formed on the testing area with a probe mark created by the testing probe. Alternatively, a semiconductor chip comprises a testing pad and a bond pad respectively exposed by two openings in a passivation layer, wherein the testing pad is connected to the bond pad. During a step of testing, a testing probe contacts with the testing pad for electrical testing. After the step of testing, a polymer layer is formed on the testing pad with a probe mark created by the testing probe.