A proven methodology for detecting photo-resist residue and for qualifying photo-resist material by measuring fluorescence using SP2 bare wafer inspection and SURFmonitor

During the chip making process, complete removal of photo-resist is very critical. Current metrology & analytical methods do not provide enough sensitivity to detect residual amounts of photo-resist remaining on the wafer. Using the novel method described in this study, the Surfscan SP2 and SURFmonitor solution has successfully demonstrated the sensitivity needed to detect residual photo-resist. This method takes advantage of the fact that residual photo-resist, which is organic in nature, will fluoresce. By scanning wafers after the ash and clean step using the SP2 (UV wavelength) unpatterned defect inspection tool equipped with SURFmonitor, it is possible to generate a full-wafer fluorescence SURFimage. This SURFimage was shown to clearly indicate the regions of the wafer where residual photoresist was present.