A Modified Interposer Fabrication Process by Copper Nano-Pillars Filled in Anodic Aluminum Oxide Film for 3D Electronic Package

Abstract

Though copper nano-pillars (CNPs) filled in anodic aluminum oxide (AAO) film has been developed for many years, the high pore-filling percentage in AAO is still a bottleneck. We have demonstrated a new electrodeposition method to fill CNPs in AAO without the seed layer which is required in the traditional electrodeposition process. CNPs with uniform heights were obtained and the pore-filling percentage reached up to 97.5%. Low current density is beneficial for the high pore-filling percentage due to the uniform growing rate in different nanoscale pores. The high temperature increased the diffusion velocity of ions and enhanced the pore filling percentage but also corroded the AAO film simultaneously. Results showed that CNPs grains with <220> orientation were fabricated. Electrodeposition with low electric current could contribute to the forming of CNPs with (220) preferred orientation due to the promotion of dehydration reduction processes. The thermal conductivities of Cu-AAO interposers reaches 92.34 W/(m·K) and 3.19 W/(m·K) in vertical and horizontal directions, respectively.

One-Step Fabrication of Copper Nanopillar Array-Filled AAO Films by Pulse Electrodeposition for Anisotropic Thermal Conductive Interconnectors

“…As shown in the inset image of Figure c, there is a noticeable shortage of Cu pillars upon where the Cu bulk presented. Though it has been reported in our previous research that low current density can alleviate the unbalanced growth of the pillars as the Cu diffusion rate can keep up with the electrodeposition rate at this status; meanwhile, the plating time is remarkably extended. Besides, considering that the overpotential is proportional with the current density, to reach the needed overpotential threshold, there is a minimum current density to trigger the deposition process.…”

Joining Technology Innovations at the Macro, Micro, and Nano Levels

“…Realized or not, it is also one of the key elements in traditional macro-welding technologies. Recently, this is being widely used in micro-and nanoscales to develop new joining processes, ranging from nanodevices [28] to electronic packaging [29,30], soldering [31] to light alloy (Ti, Al) [32,33], and high-strength steel joining [34]. The goal of design strategy is to meet the performance requirements of as-fabricated joints through the proper determination of the necessary number of IMCs, layered structures, phases, intrinsic properties of used materials (e.g., hardness, grain size, etc.…”

“…The high energy of nanomaterials also enables room-temperature joining [37] for electronic packaging through self-generated heat [38] or ultra-dense atomic defect-motivated fast diffusion [39]. Aside from heat, the control of grain orientation [30], size [40], or interfacial stoichiometry [41] during the joining process could also be employed for the engineering of the high thermal conductivity, ultrahigh yield strength, or electron transportation efficiency of interfacial structures.…”