Seshadri Ganguli

Effective Work Function Engineering for Aggressively Scaled Planar and Multi-Gate Fin Field-Effect Transistor-Based Devices with High-k Last Replacement Metal Gate Technology

This work reports on aggressively scaled replacement metal gate, high-k last devices (RMG-HKL), exploring several options for effective work function (EWF) engineering, and targeting logic high-performance and low-power applications. Tight low-threshold voltage (VT) distributions for scaled NMOS devices are obtained by controlled TiN/TiAl-alloying, either by using RF-physical vapor deposition (RF-PVD) or atomic layer deposition (ALD) for TiN growth. The first technique allows optimization of the TiAl/TiN thicknesses at the bottom of gate trenches while maximizing the space to be filled with a low-resistance metal; using ALD minimizes the occurrence of preferential paths, at gate sidewalls, for Al diffusion into the high-k dielectric, reducing gate leakage (JG). For multi-gate fin field-effect transistors (FinFETs) which require smaller EWF shifts from mid-gap for low-VT: 1) conformal, lower-JG ALD-TiN/TaSiAl; and 2) Al-rich ALD-TiN by controlled Al diffusion from the fill-metal are demonstrated to be promising candidates. Comparable bias temperature instability (BTI), improved noise behavior, and slightly reduced equivalent oxide thickness (EOT) are measured on Al-rich EWF-metal stacks.

Novel metal gates for high κ applications

The development of gate systems suitable for high κ dielectrics is critical to the advancement of complementary metal-oxide-semiconductor (CMOS) devices. Both the effective work function and material stability are key parameters to these systems. A systematic study of metal gates of the composition HfxSi1-x (0.25 ≤ x ≤ 1) is demonstrated here, including XPS, XRD and four point probe measurements. The effective work function of each material is evaluated and it is shown that it can be tuned from 4.5 to less than 4.0 eV. Suitable work functions for n-channel metal-oxide-semiconductor applications (4.05 ± 0.2 eV) were achieved using hafnium rich compositions; however, XPS and diffraction measurements confirmed that these materials demonstrated a high propensity to oxidise, causing the reduction of the underlying oxides, making them unsuitable for commercial application.

Effective Work Function Engineering for Aggressively Scaled Planar and FinFET-based Devices with High-k Last Replacement Metal Gate Tech.

Devices with High-k Last Replacement Metal Gate Technology A. Veloso, S. A. Chew, Y. Higuchi, L.-Å. Ragnarsson, E. Simoen, T. Schram, T. Witters, A. Van Ammel, H. Dekkers, H. Tielens, K. Devriendt, N. Heylen, F. Sebaai, S. Brus, P. Favia, J. Geypen, H. Bender, A. Phatak, M. S. Chen, X. Lu, S. Ganguli, Y. Lei, W. Tang, X. Fu, S. Gandikota, A. Noori, A. Brand, N. Yoshida, A. Thean, and N. Horiguchi IMEC, assignee at IMEC from Panasonic, Applied Materials Belgium NV, Kapeldreef 75, 3001 Leuven, Belgium; Applied Materials Inc., 3050 Bowers Ave., Santa Clara, CA 95054, USA Tel.: +32-16-28 17 28, Fax: +32-16-28 17 06, Email: Anabela.Veloso@imec.be