The effects of supercritical CO2 formulations on the removal of high-dose ion-implanted photoresists

Abstract

Highlights3wt.% EH-3 and TMN-3 are chosen to form scCO2 microemulsions.2vol.% DMSO and IPA can enhance HDI PR efficiency by 75.5% and 64.2%.DMSO and EH-3 show a positive synergistic effect on the stripping efficiency.scCO2 density tuned by temperature and pressure affects HDI PR stripping behavior.100% Removal efficiency is achieved at 60?C and 25MPa for 20min. A new effective method for high-dose ion-implanted photoresist (HDI PR) stripping is reported based on supercritical CO2 (scCO2) microemulsions consisting of branched hydrocarbon surfactant 2-ethylhexanol polyoxyethylene-polyoxypropylene (EH-3) and co-solvent dimethylsulfoxide (DMSO). The optimized concentrations of EH-3 and DMSO in scCO2 were 3wt.% and 2vol.%, respectively, and the weight ratio of H2O and EH-3 is 1:1. The HDI PRs containing crust layers were removed in the scCO2 microemulsions at 10-25MPa and 40-80?C for 20min. The results revealed that the stripping efficiency of HDI PR increased with the pressure and temperature (T) when T is lower than 60?C. The removal efficiency of 96.8% was achieved at 60?C and 20MPa and then it gradually decreased as T higher than 60?C due to the lower scCO2 density at higher T. Magnetic agitation was favorable for the HDI PR removal. The optimum stripping parameters were determined to be 60?C and 25MPa for 20min at which 100% removal efficiency was achieved in EH-3/DMSO/scCO2 microemulsions. This environmentally benign method provides a promising alternative to effectively strip HDI PR for devices with nano-sized feature dimensions in microelectronic processing.