Novel diagnostics for stress-depth profiling and mechanics in multi-layer thin films
Robin Martens defended his PhD thesis at the Department of Mechanical Engineering on December 19th.
The first research objective of Robin Martens was to measure the mechanical properties of thin film stacks. An improved bulge test method was developed to quickly and accurately handle membranes under both tensile and compressive stresses. This method inflates a membrane while analyzing its full-field height profile in a novel way to determine the mechanical behavior of the (multi-layer) membrane.
Advanced diagnostics
The second objective was to measure residual stress across the thickness of completed multi-layer thin film stacks, after relaxation. Existing methods are prone to errors, so a new Multi-layer Stress Depth Profiler (MLSDP) was developed. It consists of three components:
- a dedicated plasma setup that gently and homogeneously etches the multi-layer stack,
- an innovative more accurate stress sensor, using an optimized optical pattern and image correlation algorithm, that measures the change in residual stress,
- a novel, robust, automatically calibrated, monolithic microbalance, with high load capacity and resolution, that measures the weight change. This simultaneously acquired data is converted to a stress versus thickness profile of the multi-layer stack.
Data from these advanced diagnostics will help optimize the performance and production of future microelectronic devices.
Title of PhD thesis: . Promotor: Dr. Johan Hoefnagels, and Prof. Marc Geers. Co-promotor: Associate Prof. Olaf van der Sluis