Pattern formation during interfacial reaction in-between liquid Sn and Cu substrates - A simulation study
Journal
Acta Materialia
Journal Volume
113
Pages
245-258
Date Issued
2016
Author(s)
Abstract
Heteroepitaxial formation of η-Cu6Sn5 intermetallic compound (IMC) on unidirectional Cu has been found to exhibit remarkable microstructural features and provide opportunities for microstructure control of microelectronic interconnects, but the crystallographic origin and formation mechanism of such morphological patterns are still unclear. Here we investigate pattern formation during interfacial reactions in between liquid Sn and two types of unidirectional Cu substrates, (001) and (111), by using a combination of crystallographic analysis, theory of microelasticity and phase-field simulations. The simulation results show that each symmetry-related η-Cu6Sn5 variant grows along the direction of best atomic site matching with the substrates. No spatial alignment can be achieved when the growth takes place without heteroepitaxial constraints. In addition, anisotropy in interfacial energy between the liquid Sn and IMC is found to lead to faceted morphology. Further, the habit planes of η-Cu6Sn5 precipitates and kinematic compatibility across the interfaces are analyzed theoretically and found to be consistent with the simulations. These simulation predictions demonstrate excellent agreements with experimental observations.
Publisher
Elsevier Ltd
Type
journal article