Photoresist and Residue Removal Using Gas-Expanded Liquids

Rapid technology development and demands for state-of-the-art generations of integrated circuits bring new challenges to microelectronic device manufacture. Specifically, decreasing dimension sizes may limit the effectiveness of liquid-based removal of photoresist and plasma etch residues. In addition, the hazardous solvents currently in use pose environmental concerns. Gasexpanded liquids (GXLs) and supercritical fluids may offer cleaning or residue removal approaches that overcome some of the drawbacks of current surface preparation methods. Removal of PHOST (polyhydroxystyrene) photoresist films has been demonstrated with CO2-expanded ethanol (up to 75 mol % CO2), indicating that the inclusion of CO2 does not inhibit photoresist removal. In situ interferometry measurements of the PHOST layers allowed insight into the removal mechanism. The GXL mixtures were also invoked to remove post-plasma etch residues using CO2-expanded TMAHCO3/CH3OH. At a temperature of 90DGC and pressures above 1000 prig the GXL mixture removed the photoresist and etch residue. Cleaning efficiency depended on CO2 pressure; at lower pressures the CO2 reduced the mole fraction of the TMAHCO3/CH3OH while at higher pressures the CO2 assisted removal.