Dielectric and Metal Materials for Redistributed Layers: Thermo-Mechanical Properties and Challenges for Advanced Packaging

Redistribution layers (RDL) play an important role in advanced packaging technologies for integrated circuits (IC). The primary objective of the RDL is to redistribute the input/output (I/O) pads of a chip to a different layout or pitch, allowing for efficient and compact interconnections with other chips or package-level interconnects. The interconnects made of metal, like copper, are embedded in a dielectric, which acts as insulation between the metal traces and provides mechanical support.

As IC packages are composed of different materials, with different coefficient of thermal expansion (CTE). When the packages are exposed to temperature changes, during their fabrication or their operation, the materials expand or contract at different rates due to their mismatch in CTE. This can lead to stress buildup in the RDL, potentially causing failure or delamination.

Addressing thermal-mechanical stresses in RDL design and manufacturing processes is crucial to ensure the reliability, performance, and longevity of IC packages. By mitigating these stresses, one can minimize the risk of failures, improve signal integrity, and enhance the overall robustness of the IC package.

The goal of this PhD is to investigate the reliability challenges associated with RDL structures in IC packages and develop techniques for their reliability assessment. The candidate will build finite element (FE) models in order to predict thermal-mechanical stresses and failure. He/she will conduct experimental characterization of materials and interfaces to extract the parameters needed for the FE models he/she will develop.

This position is well-suited for candidates from mechanical engineering, material science, physics, or similar fields, who have a strong interest and background in numerical modelling and experimental techniques. It is preferable that the candidate have a good knowledge of finite element modelling (FEM). Experience with a FEM software such as Ansys, Abaqus or Msc. Marc is of added value. A genuine enthusiasm for multidisciplinary research is required. This PhD topic is centered around semiconductor technology, providing the student with valuable opportunities to collaborate and gain exposure to diverse teams and research programs.