A novel, three-step dry etching process for the fabrication of first-order diffraction gratings in III-V semiconductors is reported. The process takes advantage of the etching of thin films of SiO2 and of a sensitive, organosilicon electron-beam resist by the H2/CH4 plasma. It reduces wafer handling and eliminates wet stripping of the resist. The gratings were imaged with a scanning tunnelling microscope.