Selective dry etching of attenuated phase-shift mask materials for extreme ultraviolet lithography using inductively coupled plasmas

Among the core extreme ultraviolet lithography (EUVL) technologies, mask fabrication is of considerable importance due to the use of new reflective optics having a completely different configuration from that of conventional photolithography. This study investigated the etching properties of attenuated phase-shift mask materials for EUVL, such as TaN (attenuator layer), Al(2)O(3) (spacer), Mo (phase shifting layer), Ru (buffer/capping/etch-stop layer), and Mo-Si multilayer (reflective layer) by varying the Cl(2)/Ar gas flow ratio, dc self-bias voltage (V(dc)), and etch time in inductively coupled plasmas. For the fabrication of the attenuated EUVL mask structure proposed herein, the TaN, Al(2)O(3), and Mo layers need to be etched with no loss of the Ru layer on the Mo-Si multilayer. The TaN and Al(2)O(3) layers were able to be etched in BCl(3)/Cl(2)/Ar plasmas with a V(dc) of -100 V and the Mo layer was etched with an infinitely high etch selectivity over the Ru etch-stop layer in a Cl(2)/Ar plasma with a V(dc) of -25 V even with increasing overetch time.This research was financially supported by the EUVL R&D Research Fund of the Ministry of Knowledge Economy (MKE). This work was also partially supported by Korea Institute for Advancement of Technology (KIAT) through the Human Resource Training Project for Strategic Technology and by the National Research Foundation of Korea (NRF) through Basic Science Research Program (20090083540) and WCU Program (R32-2008-000-10124-0). The authors also wish to thank H. K. Cho, S. S. Kim, and H. S. Seo at Samsung Electronics for their useful contributions