Post ion-implant photoresist removal via wet chemical cleans combined with physical force pretreatments

Abstract

A combination of wet chemistry and high-velocity solid CO2 aerosol pre-treatment was used to remove ion-implanted resist from patterned Si structures. The top resist surface is modified by heavy ion-implantation (1×1016 As atoms/cm2, 40keV) forming a crust ∼100nm thick. The aerosol treatment, which is aimed at breaking and partially removing the crusted top layer of implanted resist, produces circular openings in this surface, with diameters on the order of tens to hundreds of micrometers. No resist is detected by either optical microscopy or localized SEM inspection, after immersion in hot H2SOVH2O2 mixture (SPM), on aerosol-pretreated wafer fragments. In contrast, resist residue is still observed on similarly pre-treated specimens, after immersion in either N-methyl pyrrolidone or Microstrip2001™, even under ultrasonic agitation. Overall, the aerosol pre-treatment is a key step in reducing the amount of resist residue, for both aqueous-based and solvent-based wet cleaning. Full-wafer defect-count results, post aerosol treatment, are reported for poly-Si line widths down to 40 nm. © The Electrochemical Society.