High-resolution ion depth profiling: beyond high-k materials

Department of Physics and Astronomy, University of Western Ontario, London, Ontario, N6A 3K7 Canada

Progressive reduction of dimensions and introduction of novel materials in sub-32 semiconductor technology nodes demands continuous improvement in high-resolution ion depth profiling (HRDP). One of the challenges here is that electron transport properties of these diverse materials are closely linked to the basic interactions at the interface. We will demonstrate novel application of HRDP methods, including medium energy ion scattering (MEIS), low energy ion scattering (LEIS), nuclear reaction profiling (NRP) and secondary ion mass spectrometry (SIMS) to high-k/metal gate, high-mobility (III-V) channel materials and ultra-shallow junctions. We will present the application of MEIS in combination with O-18 isotope labeling to follow oxygen migration in high-k/metal gate ultra-thin stacks.

Recently it was established that deposition of an oxygen-gettering overlayers such as Ti on top of the high-k metal oxide can result in reduction and even possibly elimination of the interfacial layer. Both oxygen exchange and interfacial silicon oxides growth rates were examined as a function of time, temperature, chemistry and crystallinity of dielectric layer. We find that incorporation oxygen is suppressed with addition of silica and nitrogen. Whereas presence of interstitials (O2-, OH-) is responsible for the fast O incorporation at the interface and interfacial oxide growth. We will also discuss application of complementary low-energy ion scattering and time-of-flight SIMS surface analysis to determine (a) high-k thin film growth mode for different deposition techniques; (b) the feasibility of backside SIMS on III-V high-mobility channel stacks to obtain high depth resolution at the source/drain /III-V interface.