PhD

Process Technology

• Ge and III-V CMOS scaling
• Post-CMOS nano
• Reliability research at imec
• Memories
• Power devices
• GaN Power Converters
• Nanoscale properties of new materials for emerging memory de
• Ion-solid interactions
• Probing semiconductor devices on the atomic scale
• Packaging and interconnection
• SiGe-based MEMS
• RF-MEMS
• Advanced lithography
• Simulation of wafer plating uniformity
• Superfilling of 3D via structures with alternative metals
• Diamond bit cutting for metal bonding

Diamond bit cutting for metal bonding

A promising new technique has emerged for surface treatment in micro-electronic 3D applications. Layers on a wafer can be planarized and their roughness reduced by diamond bit cutting. This technique is compatible with post-passivation processing and shows potential to enable alternatives to solder based bumping. For example, thermo-compression bonding of cut Au surfaces has been reported at temperatures as low as 180ºC.

However, as the technique is new in this application, a lot of factors remain unknown. Areas of research therefore include:

• Characterization of the machining process: effect of the cutting parameters on surface roughness, influence of material hardness, ...
• Effect of the cutting process on the underlying layers: characterize the damage caused by the process; understand forces exerted during cutting and how they propagate through different layers.
• Characterization of interfaces after bonding: mechanical testing (tensile or shear strength), grain growth at bonded interfaces, influence of oxides or other surface contaminations.

The insights gained through this research will allow to develop a strategy for optimizing quality of the cutting process for different materials and combinations of materials.