Advances in Selective Wet Etching for Nanoscale NiPt Salicide Fabrication

Currently, the two-step rapid thermal process (RTP) which includes a lower temperature RTP 1 and a larger amount of platinum (Pt) additive is the trend to form thinner nickel monosilicide (NiSi) for the NiPt silicide scaling together with complementary metal oxide semiconductor (CMOS) technology toward the 22 nm node. In this work, we re-investigate the piranha chemistry and match the Pt oxidation/dissolution behavior to develop a piranha chemistry base wet etching process. The result shows that higher temperature preheated sulfuric acid Piranha will boost the reaction rate drastically. Also, the two-time Pt additive will take three-time process time to clear the Pt residue. Compare to the traditional chloric acid base process, the new Piranha process has achieved the goal of effective Pt removal, lower material loss and no damage to nickel-rich silicide (Ni 2 Si/Ni 3 Si 2 ). It results in a lower and more uniform silicide sheet resistance ( R S ) on both n/pMOS.