Highly anisotropic and corrosion-less PtMn etching was achieved for the first time by using a pulse-time-modulated (TM) chlorine electron-cyclotron-resonance plasma. It was found that PtMn etching rate, in the case of the TM plasma, increased considerably compared with that in the case of a conventional continuous-wave plasma. The formation of etching residue and post-etch corrosion products was reduced by increasing the pulse-off time of the TM plasma. Moreover, surface analysis showed that the residual chlorine concentration decreases during the TM plasma etching. In addition, hydrogen-plasma post-exposure treatment after the etching process could decrease the residual chlorine concentration and suppress post-etch corrosion product formation. It is concluded from these results that when combining TM chlorine plasma etching and the hydrogen-plasma post-exposure treatment one can successfully pattern highly anisotropic vertical etched profiles with sub-micron width and no critical-dimension loss. (C) 2004 American Vacuum Society.