Abstract: A method of manufacturing a wafer is disclosed. The method includes the steps of: (a) providing a substrate on which a number of semiconductor devices are formed and covered with a passivation layer; (b) exposing a number of contact pads in connection with the semiconductor devices by etching a portion of the passivation layer which are corresponding to the contact pads; and (c) cleaning the contact pads by soaking the substrate into a nitric acid solution and than rinsing. The concentration of the nitric acid solution can be about in the range between 0.01 vol. % and 30 vol. % and preferably about in the range between 1 vol. % and 10 vol. %. Thus, defects on wafers are greatly reduced with causing damages.