Pulsed microwave plasma etching of polymers in oxygen and nitrogen for microelectronic applications

Gaseous plasma generated by a half-wave rectified power supply are characterized and applied to the etching of photoresist and polymide in oxygen, dry air, or air. Activation energies of 8.6 kcal/mole and 10.9 kcal/mole are calculated for oxygen plasma etching of photoresist and polyimide, respectively. An average power of 625 W at 2.45 GHz is supplied by a magnetron through a rectangular waveguide to a 51-mm diameter quartz tube generating pulsed plasmas in oxygen and nitrogen at pressures between 0.1 torr and 10 torr with a repetitive rate of 60 Hz. The plasmas are studied by a double Langmuir probe and an optical emission spectrometer. Polymers placed in the downstream of the plasma are etched at high rates, especially when external heating is applied to raise the sample temperature. The characteristics of the plasmas and the application to the fast etching of polymers are discussed.<>