Advanced Surface Cleanliness Evaluation Technique For Sub-32nm Nodes Using Epitaxial Silicon Germanium (Sige)

Epitaxial growth process strongly depends on the substrate surface cleanliness. In this study, advanced surface cleanness evaluation techniques for 32nm node and beyond such as light point defects (LPDs) and haze measurements are studied using epitaxial silicon germanium (SiGe) process on 300mm wafers. Small water marks formed during wafer drying can be detected as small LPDs just after pre-cleaning. These water marks inhibit SiGe growth during the epitaxial process. In addition, SiGe film LPDs increase drastically with increasing queue time between pre-cleaning process and SiGe CVD process. Finally, SURFimage haze measurement is shown to be a powerful advanced technique to monitor the localized "abnormal growth defects" and the surface morphology of the SiGe CVD film over the full wafer surface.