Rapid Synthesis of Sub-10 nm Hexagonal NaYF4-Based Upconverting Nanoparticles using Therminol® 66

We report a simple one-pot method for the rapid preparation of sub-10 nm pure hexagonal (β-phase) NaYF4-based upconverting nanoparticles (UCNPs). Using Therminol® 66 as a co-solvent, monodisperse UCNPs could be obtained in unusually short reaction times. By varying the reaction time and reaction temperature, it was possible to control precisely the particle size and crystalline phase of the UCNPs. The upconversion (UC) luminescence properties of the nanocrystals were tuned by varying the concentrations of the dopants (Nd3+ and Yb3+ sensitizer ions and Er3+ activator ions). The size and phase-purity of the as-synthesized core and core–shell nanocrystals were assessed by using complementary transmission electron microscopy, dynamic light scattering, X-ray diffraction, and small-angle X-ray scattering studies. In-depth photophysical evaluation of the UCNPs was pursued by using steady-state and time-resolved luminescence spectroscopy. An enhancement in the UC intensity was observed if the nanocrystals, doped with optimized concentrations of lanthanide sensitizer/activator ions, were further coated with an inert/active shell. This was attributed to the suppression of surface-related luminescence quenching effects

CMP process development for Cobalt liner integration at the 28-nm-node

Advanced liner materials are crucial for optimizing and further shrinking of integrated circuits' interconnects. For next generation devices there is a focus on Cobalt (Co) and Ruthenium (Ru) [1]. Besides the challenges to deposit such materials, new chemical-mechanical polishing (CMP) process compatibility is needed. Especially Co introduces a bunch of new requirements. To reach the advantages of improved step coverage and lowered electrical resistivity compared to Tantalum nitride (TaN) [2] a complete change in consumables is needed to prevent Co from corrosion. Different CMP consumables are tested in a newly established 28 nm Co integration flow with special focus on corrosion properties and electrical performance. Starting from a standard TaN/Ta barrier process the corresponding consumables are systematically changed from non- Co compatible to Co compatible alternatives. Eventually the polishing steps are tuned to meet the integration requirements