(Invited) Contacts in Advanced CMOS: History and Emerging Challenges

Monday, 29 May 2017: 14:00
Churchill B2 (Hilton New Orleans Riverside)
C. Lavoie (IBM Research), P. Adusumilli (IBM Semiconductor Research and Development Center), A. V. Carr (IBM Research), J. S. Jordan Sweet (IBM T. J. Watson Research Center), A. S. Ozcan (IBM Research), E. Levrau (IBM T. J. Watson Research Center), N. Breil, and E. Alptekin (IBM Semiconductor Research and Development Center)
With the continued evolution of CMOS technologies, which includes recent changes in both device geometries and contact schemes, contact lengths of advanced devices are now reaching below 20 nm. At these dimensions, material microstructure (grain size) becomes similar to contact size and interface quality becomes critical to device performance. The sustained reduction in contact size together with the complications associated with the introduction of non-planar devices have recently lead to drastic modifications in process flow for the contacts. These new process schemes have altered the materials requirements for the contacts to the point where two factors dominate material selection: a low intrinsic contact resistivity interface and a higher morphological stability. As a result, advanced CMOS development has unexpectedly made a return to contacts based on titanium. In this presentation, we will first describe the evolution of materials used for contacts through the scaling of CMOS technologies. We will discuss what is observed in the titanium thin films when annealed under various advanced treatments as the metal film thickness is reduced below 10 nm.