Hydrogen plasma removal of post-RIE residue for backend processing

Reactive ion etching of a patterned silicon dioxide layer leaves behind a uniform fluorocarbon layer which must subsequently be removed. Both surface and via polymeric residues form during the reactive ion etch step and their removal using H₂-based plasma clean processes is reported here. X-ray photoelectron spectroscopy was used to determine the composition of the residue. Scanning electron microscope images were taken before and after the dry clean treatment to determine the effectiveness of the residue removal process. A radio-frequency-generated hydrogen plasma was used in the dry clean experiments. Power, temperature, and pressure were varied while gas flow was kept constant at 75 sccm and the process time was 5-10 min. The surface residue (on the oxide) was most efficiently removed at 400 W, 450°C, and 15 mTorr when exposed to the plasma for 10 min. The in-via residue was best removed following a 5 min plasma exposure at 100 W, 450°C and 15 mTorr.