AVS 63rd International Symposium & Exhibition
    Thin Film Wednesday Sessions
       Session TF+EM+MI-WeA

Paper TF+EM+MI-WeA2
Study of Ru Silicidation with and without Sub-nm ALD TiN and TaN Barrier/nucleation Layers for Ru Interconnect Applications

Wednesday, November 9, 2016, 2:40 pm, Room 105A

Session: Thin Films for Microelectronics
Presenter: Sonal Dey, SUNY College of Nanoscale Science and Engineering
Authors: S. Dey, SUNY College of Nanoscale Science and Engineering
K.-H. Yu, TEL Technology Center, America, LLC
S. Consiglio, TEL Technology Center, America, LLC
K. Tapily, TEL Technology Center, America, LLC
C.S. Wajda, TEL Technology Center, America, LLC
G.J. Leusink, TEL Technology Center, America, LLC
J. Jordan-Sweet, IBM T.J. Watson Research Center
C. Lavoie, IBM T.J. Watson Research Center
A.C. Diebold, SUNY College of Nanoscale Science and Engineering
Correspondent: Click to Email
With continual shrinkage of the feature size in devices, contribution of the Cu interconnects, liners, and barrier layers to the RC time-delay is becoming a significant obstacle at the 10 nm technology node and below. Ru is a potential candidate to replace Cu as an interconnect material for ultra-scaled line widths where scaling effects on Cu line resistance become increasingly problematic. Ru has already been demonstrated to be useful as the seed layer for Cu electroplating but has been shown to be an inadequate barrier to prevent Cu diffusion into surrounding BEOL dielectrics and requires the use of an additional barrier layer such as a Ta-based nitride. In addition, TaN deposited by PVD is reaching a limit in its ability to conformally coat aggressively scaled structures in the sub 10 nm node. Accordingly, in this study we evaluated the thermal stability of thin Ru films (3 nm) with and without ultra-thin (~0.5 nm) highly conformal ALD TiN and TaN films as nucleation and/or barrier layers for Ru interconnect applications in advanced technology nodes. Si (100) substrates were chemically cleaned to remove the native oxides followed by deposition of ultra-thin ALD TiN and TaN barrier films. TiCl4 and Ta(NCMe3)(NEtMe)3 precursors, along with NH3, were used for deposition of the TiN and TaN layers, respectively. Using Ru3(CO)12, 3 nm of Ru was deposited by CVD on top of these refractory metal nitride films and also directly on Si. We also used PVD Cu (25nm)/Si as a control stack for our experiments. The diffusion kinetics of metal-silicide formation was evaluated using in-situ rapid thermal anneal (RTA) synchrotron x-ray diffraction (XRD) measurements and a Kissinger-like analysis to determine the transition temperatures of the metal-silicidation in these stacks and the effective activation energy (Ea) using three different ramp rates (0.3, 3, and 10 °C/s). The Ru/Si stack showed higher Ea = 2.48 eV as compared to the Cu/Si stack (Ea = 1.88 eV). A 0.5 nm thick TaN (Ea = 2.88 eV) was found to act as a more effective barrier as compared to 0.5 nm thick TiN (Ea = 2.64 eV). Scanning electron microscopy (SEM) data shows that both TaN and TiN act as nucleation layers for the growth of Ru microstructure on top. A fewer number of pin holes was observed for Ru films deposited on TaN although there was not significant change on the wettability properties of the Ru film with either TiN and TaN nucleation layers underneath. Additional physical and chemical characterization with XPS and TOF SIMS were also performed to gain understanding of the film stack properties before and after silicide formation.