Direct-Liquid-Evaporation Chemical Vapor Deposition of Nanocrystalline Cobalt Metal for Nanoscale Copper Interconnect Encapsulation

Electron beam-induced demetallation of Fe, Co, Ni, Cu, Zn, Pd, and Pt metalloporphyrins: insights in e-beam chemistry and metal cluster formations

Electron beams are versatile tools for nanoscale fabrication processes, however, the underlying e-beam chemistry remains in its infancy. Through operando transmission electron microscopy investigations, we elucidate a redox-driven cargo release of individual metal atoms triggered by electron beams. The chosen organic delivery molecule, tetraphenylporphyrin (TPP), proves highly versatile, forming complexes with nearly all metals from the periodic table and being easily processed in solution. A comprehensive cinematographic analysis of the dynamics of single metal atoms confirms the nearly instantaneous ejection of complexed metal atoms under an 80 kV electron beam, underscoring the system's broad versatility. Providing mechanistic insights, we employ density functional theory to support the proposed reductive demetallation pathway facilitated by secondary electrons, contributing novel perspectives to electron beam-mediated chemical reaction mechanisms. Lastly, our findings demonstrate that all seven metals investigated form nanoclusters once ejected from TPP, highlighting the method's potential for studying and developing sustainable single-atom and nanocluster catalysts.

Effect of encapsulation on electronic transport properties of nanoscale Cu(111) films

The stiff compromise between reliability and conductivity of copper interconnects used in sub-nanometer nodes has brought into focus the choice of encapsulation material. While reliability was the primary driver so far, herein, we investigate how electronic conductivity of Cu(111) thin films is influenced by the encapsulation material using density functional theory and Boltzmann transport equation. Atomically thin 2D materials, namely conducting graphene and insulating graphane both retain the conductivity of Cu films whereas partially hydrogenated graphene (HGr) results in reduction of surface density of states and a reduction in Cu film conductivity. Among transition metal elements, we find that atoms in Co encapsulation layer, which essentially act as magnetic impurities, serve as electron scattering centres resulting in a decrease in conductivity by at least 15% for 11 nm thick Cu film. On the other hand, Mo, Ta, and Ru have more favorable effect on conductivity when compared to Co. The cause of decrease in conductivity for Co and HGr is discussed by investigating the electronic band structure and density of states. Our DFT calculations suggest that pristine graphene sheet is a good encapsulation material for advanced Cu interconnects both from chemical protection and conductivity point of view.

Experiment-based modelling of a vapor draw ampoule used for low-volatility precursors

Delivery of low-volatility precursors is a continuing challenge for chemical vapor deposition and atomic layer deposition processes used for microelectronics manufacturing. To aid in addressing this problem, we have recently developed an inline measurement capable of monitoring precursor delivery. Motivated by a desire to better understand the origins of what is now observable, this study uses computational fluid dynamics and a relatively simple model to simulate the delivery of pentakis(dimethylamido)tantalum (PDMAT) from a commercial vapor draw ampoule. Parameters used in the model are obtained by fitting the performance of the ampoule to a limited dataset of PDMAT delivery rates obtained experimentally using a non-dispersive infrared sensor. The model shows good agreement with a much larger experimental dataset over a range of conditions in both pulsed and continuously flowing operation. The combined approach of experiment and simulation provides a means to understand the phenomena occurring during precursor delivery both quantitatively and qualitatively.

From the source: student-centred guest lecturing in a chemical crystallography class

Guest lecturing is an underutilized teaching strategy that provides depth and richness in college-level chemistry courses. The authors have found that student-centred guest lecturing that combines themed guest presentations, hands-on workshops (whenever possible) and small group conversations has yielded tremendous benefits. As a result, students have developed a lasting interest in chemical crystallography and have employed advanced experiments in their own research. The authors report on their experience in planning student-centred guest lecturing, advise on best practices, and demonstrate the long lasting positive impact on student learning and engagement.