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

Superfilling of 3D via structures with alternative metals

Over the past decade, electroplating has become a popular technique in the manufacturing of silicon chips. The popularity is in large part due to the invention of the copper damascene process by IBM. In that process, small features are filled with copper by electroplating. Filling small, narrow features requires a bottom-up fill or so-called superfilling mechanism for the deposition process.

The superfilling mechanism is now well established for features up to 1 micrometer in size. Currently, the technique is being extended to far larger features, up to 100 micrometer in diameter. Next to ongoing extension in sizes, it will in the future be useful to apply it to materials other then copper. Determining the applicability of superfilling to electroplating systems beyond copper will therefore be the subject of this work. Alternative materials may have several advantages. For example, diffusion barriers would be unnecessary if the copper could be replaced by nickel (Cu is a major contaminant in Si devices; Ni is not). Also, a metal with less thermal expansion coefficient mismatch with silicon would avoid the accumulation of stresses that is now a problem with copper filled features.