Selective Etching of Bilayer Photoresist Using a Multipolar Electron Cyclotron Resonance Source

An oxygen plasma generated by a multipolar electron cyclotron resonance plasma source has been used to provide fast and residue-free pattern transfer for a 193 nm bilayer resist scheme. The etch rates of the silicon-containing imaging layer and the carbon-based planarizing layer and the final etch profile were studied as a function of microwave power, pressure, RF power to the wafer chuck, and source to sample distance. The etch rate of the planarizing layer (hard-baked Shipley AZ1813) increases with increasing microwave power and/or RF power to the wafer chuck but decreases as the sample is moved further from the plasma source. The thin (<40 nm) silicon-containing imaging layer did not erode during pattern transfer except when high ion energy or high ion flux was used. Vertical profiles have been obtained for features as small as 0.1 μm at etch rates ~1 μm/min.