High-dose ion-implanted photoresist stripping in environmentally benign supercritical CO2 nonfluorous surfactant microemulsions

The stripping behavior of high-dose ion-implanted (HDIM) photoresist was investigated in a scCO2 microemulsion with 3 wt.% surfactant of 2-ethyl hexanol polyoxyethylene–polyoxypropylene and 2 vol.% co-solvent of dimethylsulfoxide. The removal efficiency was studied under the pressure of 10–25 MPa at 40–60 °C. The results of surface characterization and composition analysis for the cleaned samples by SEM, FTIR, and XPS revealed that the removal rate increased with time with a sharp increase during the first 10 min. Temperature and pressure are favorable to the stripping within 20 min. The photoresist removal efficiency at 50 °C improved from 40% to 85% as the pressure range of 10–25 MPa due to the higher scCO2 density at higher pressure which enhances the photoresist solubility in scCO2. The magnetic agitation and pressure pulsation generated a higher fluid velocity to provide a larger physical force. This new environment-friendly photoresist stripping method allows dramatic reduction in water and chemicals consumption and overcomes the obstacle in the conventional microelectronics processing due to the shrinkage in the feature size.

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► High-dose ion-implanted photoresist was stripped in a 3 wt.% scCO2 microemulsion.
► The microemulsion includes a nonfluorous branched surfactant and a co-solvent.
► The removal rate increased with time, temperature, and pressure.
► The magnetic agitation and pressure pulsation are favorable to the stripping.
► Hundred percentage stripping efficiency is achieved at 60 °C and 25 MPa for 20 min.