Dependence of Photoresist and Etch Residue Removal on CO2 Pressure in Alcohol-Based Gas-Expanded Liquids

Abstract

With rapid technology development of integrated circuits, new challenges arise. Current liquid based removal chemistries are limited by continuous decrease in feature devices as well by their hazardous nature. Gas expanded liquids (GXLs) and supercritical fluids may offer a more environtmentally benign alternative. The GXL formulated by CO2 expanded ethanol (up to 75 mole % CO2) removed PHOST (polyhydroxystyrene) photoresist film indicating that the inclusion of CO2 does not inhibit photoresist removal. In situ interferometry measurements of the PHOST layers generated insight into the removal mechanism. The GXL CO2 expanded TMAHCO3/CH3OH at a temperature of 90oC and pressures above 1000 psig removed photoresist and post plasma etch residue. Cleaning efficiency depended upon CO2 pressure; at low pressures the CO2 reduced the mole fraction of the TMAHCO3/CH3OH while at higher pressures the CO2 assisted removal.