Disclosed herein is a method for etching a face of an object and more particularly a method for etching a rear face of a silicon substrate. The object having a silicon face is positioned so as to be spaced apart from a plasma-generating member by a predetermined interval distance. The plasma-generating member generates arc plasmas to form a plasma region. A reaction gas is allowed to pass through the plasma region to generate radicals having high energies and high densities. The radicals react with the object to etch the face of the object. The face of the object can be rapidly and uniformly etched.