Stability of Cu-islands formed on Si substrate via ‘dewetting’ under subsequent thermal cycling

Abstract

Very thin metallic films deposited on a substrate often dewet upon thermal exposure, forming discrete islands of micrometer and nanometer-sized metal particles. Herein, Cu islands on Si substrate, which were formed due to agglomeration (or ‘dewetting’) of Cu thin film at 600 °C, were exposed to thermal cycling, and the ensuing evolution in their morphology was monitored. Thermal cycling was performed between either −25 °C and 150 °C or 25 °C and 400 °C, using different heating and cooling rates. With faster heating-cooling rates, a change in the shape and size of the Cu islands was observed, whereas a slow heating-cooling rate did not induce noticeable effect on their morphology. Furthermore, the formation of new nano- and micro-sized particles, probably through the dewetting of the ultra-thin layer of Cu that was left intact during the initial agglomeration treatment, was observed during the thermal cycling performed at fast rates up to 400 °C. Finite element analysis, incorporating Anand’s viscoplasticity model, revealed the existence of high strain energy density in the vicinity of the particle-Si interface when the thermal cycling is carried at a faster ramp rate, suggesting the pivotal role of thermal stresses, in addition to the maximum temperature, in controlling the morphology of the Cu particles and the dewetting of the residual ultra-thin layer of Cu on Si.

Decomposition and Dewetting of Super-Saturated Cu-15 at. % Cosolid Solution Film

“…Although we did not observe the initiation of dewetting in the alloyed CuCo film at 673 K, Derkach et al [14] have observed hole formation in a pure Cu film of similar thickness already at 573 K after annealing for 30 min. Additionally, Sonawane and Kumar [36] have observed complete agglomeration of a 100 nm thick Cu film into particles and islands after annealing at 873 K for 2 h. From what has been discussed earlier, we can conclude that the formation of Co precipitates at the grain boundaries in the CoCu film activates the Zener drag force and causes the stagnation of grain size below R c . As a result, the film does not dewet at the mentioned temperatures (673 and 873 K) by the grooving mechanism.…”

Restructuring and Reshaping of CsPbX3 Perovskites by Lithium Salts

“…The film transformation generally begins with pin‐holes or voids that are created at junction points between several crystal grains. The perovskite films visually behave the same way as copper thin films do when treated to high temperature, [ 21,22 ] with the film showing weak cohesive energy, forming larger grains driven by minimizing surface energy. The 75 nm passivated films were used for XRD analysis.…”