Studying the applicability of amorphous metal alloys as interface material for power electronics packaging

Abstract

All-atom Molecular Dynamics simulations were used to study the coefficient of thermal expansion (CTE) in Cu/Zr amorphous alloys with various compositions. We explored the possibility of using these alloys as bonding interface material between ceramics chips and copper leads in power electronics and microelectronic packaging applications with an objective of reducing CTE mismatch at the bonding interface. It was expected that with the appropriate design of reduced CTE mismatch at the interface, the Cu/Zr bonding layer could withstand larger thermal loads and significantly extend device life compared to the devices that currently implement directly bonded copper (DBC) approach. The non-monotonic increase of material CTE with copper content in the alloy was analyzed and explained using new tessellation algorithm that is focused on the configuration of close contacts between the neighboring atoms. The modeling using Turner equation shows that the “leveling” of CTE dependence in the mid-composition range is due to the contribution from non-tetrahedral polyhedra and would be expected for any binary glass system. Contrary to that, the “dip” at Cu-rich compositions is caused by the nature of the metallic bonding in the alloy, and is specific to Cu-Zr glass.