Film thickness mediated transition in the kinetics of electric current induced flow of thin liquid metal films

Abstract

Application of high electric-field between two points in a thin metallic film results in liquefaction and subsequent flow of the liquid-film from one electrode to another in a radially symmetric fashion. Here, we report the transition of the flow kinetics driven by the liquid film thickness varying from 3 to 100 nm. The mechanism of the flow behavior is observed to be independent of the film thickness; however, the kinetics of the flow depends on the film thickness and the applied voltage. An analytical model, incorporating viscosity and varying electrical resistivity with film thickness, is developed to explain the experimental observations.

Electrolithography- A New and Versatile Process for Nano Patterning

“…Subsequently, a Cr film of thickness 10 nm to 30 nm is deposited over the PMMA polymer layer by radio frequency (RF) magnetron sputtering. The range of 10 to 30 nm thickness for the Cr film is chosen because: the liquid Cr compound flow velocity is low for low thickness films 17 , which makes the electromigration induced etching process more controllable. However, very thin films are highly resistive wherein, while operating under constant voltage mode, the current becomes too low to melt the material and ensue the subsequent flow.…”

“…This corresponds to a current density of ~3.3 × 10 9 A/m 2 in the thin Cr film at a distance of 10 μm away from the probe tip. Such a flow is attributed to electromigration because (i) the observed material flow is directional (i.e., it occurs at only one of the two electrodes), (ii) directionality of the flow depends on the material (e.g., the flow occurs from the cathode probe for Cr and from the anode probe for Al), (iii) flow occurs along or in the reverse direction of the electric field lines, and (iv) the dependence of flow rate on the electric current and the temperature are linear and exponential, respectively, as predicted by the standard electromigration theory 16 17 .…”

“…In this work, we introduce a new lithography technique that we call Electrolithography . For developing this process, we exploit as well as significantly extend our previously reported 16 17 understanding of controlled nanoscale material transport and pattern formation due to liquid electromigration in thin metal films. We apply this phenomenon to develop a scanning probe based lithography technique where liquid electromigration driven material removal is used as a key step.…”

The formation of heterointerface defects in Au/Cu films on Si substrates under direct current in a vacuum ultraviolet environment

“…The results show that partial Cu clusters migrated in the opposite direction to electron motion and partial Au clusters migrated in the same direction as electron motion, due to the momentum transfer between the electrons and the Cu clusters of positive charge and the Au clusters of negative charge. 23,35 Besides, it was obvious that the effect of electromigration played a major role in the diffusion mechanism under DC in a vacuum UV environment. The UV radiation in the coupling effect mainly caused the change of the surface structure in the films, which induced the directed diffusion of Cu atoms to some extent.…”

“…15 Until now, there has been little research into chemical structure analysis of the surface and interfaces of multilayer films under DC in a vacuum UV environment, or on the formation mechanism of defects at the heterointerfaces in multilayer metallic thin films. [22][23][24][25][26][27] In addition, advanced surface analysis tools, such as Auger electron spectroscopy (AES) and resolution transmission electron microscopy (HRTEM), can provide valuable information about structural differences at the interfaces and details of the atomic layer structures. 16,[28][29][30][31] In this study, we use a model sample, Au/Cu/Si(100), and mainly investigate the defect formation at the heterointerfaces and the evolution of interface structure induced by DC in a vacuum UV environment using AES and HRTEM.…”