The Stripping Behavior of High-Dose Ion-Implanted Photoresists in Supercritical CO_2 Formulations

摘要

A new type of high-dose ion-implanted photoresist (HDI PR) stripping method was reported based on supercritical CO_2 (SCCO_2) microemulsions consisting of branched hydrocarbon surfactant 2-ethyl hexanol polyoxyethylene-polyoxypropylene (EH-3) and co-solvent dimethylsulfoxide (DMSO). The optimized concentration of EH-3 and DMSO in SCCO_2 were 3 wt% and 2 vol.%, respectively, and the ratio of H_2O and EH-3 is 1:1. The post-etch HDI PRs containing crust polymer were removed in the SCCO_2 microemulsions under the pressure of 10-25 MPa at 40-80°C for 10 min. The results revealed that the stripping efficiency increased with the pressure and temperature when the temperature is lower than 60°C. The 94% removal efficiency was achieved at 60°C and 20 MPa and then it gradually decreased as the temperature is higher than 60° C due to the lower SCCO_2 density at higher temperature. The magnetic agitation and pressure pulsation were favorable to HDI PR removal. The optimum stripping parameters were determined to be 60°C and 25 MPa for 20 min at which 100% photoresist removal efficiency was achieved in EH-3/DMSO/scCO_2 microemulsions. This environmentally benign method provides a promising alternative to effectively strip the HDI PR for nano-sized devices in microelectronics processing.