Research & development - Leuven | More than two weeks ago
Chemical mechanical polishing (CMP) has become a key step in microelectronic device fabrication: In the deposition step before CMP, an overburden of material is deposited to fill structures with metal material. During CMP, this overburden is removed, removing all metal from the field area while leaving the material inside the trenches untouched (no metal loss). In order to produce faster and more powerful commercial microprocessors, ‘new’ challenging materials such as copper, ruthenium, cobalt, manganese and their alloys need to be polished. For Cu-barrier CMP for example, copper etching should be limited and galvanic corrosion between the copper and barrier materials needs to be minimized. In order to design a CMP process that can achieve this, the chemical reactions that occur between the materials and the CMP slurry need to be understood and controlled.
The scope of this study is to develop a CMP process for the polishing of new materials and to gain a better understanding of the mechanisms that govern this CMP process. The polishing environment is mainly controlled by two factors: the specific materials to be polished and the CMP slurry.
The type and combination of materials, the thickness as well as the deposition (e.g. chemical vapor deposition (CVD), physical vapor deposition (PVD), electroless deposition (ELD) or electroplating) and annealing method can be crucial in determining CMP performance. A (metal) CMP slurry uses oxidizers, complexating agents, inhibitors and pH adjusters to achieve a fine balance of chemical reactions that remove material at the surface while keeping corrosion under control by passivating the newly exposed surface during polishing. In this project the effect of various slurry components will be studied both during polishing on our experimental polisher and in a static slurry solution in a lab environment. Surface analysis techniques like X-ray spectroscopy (XPS), X-ray diffraction (XRD) and nano-indentation will provide the necessary extra information to understand which reactions and species are dominant at the surface. The analysis of the data will provide the understanding needed to design a model slurry which polishes the material away at a decent rate while achieving a good quality surface.
If the model slurry design experiments are succesful, the efficiency of the optimized slurry will be tested on blanket and/or patterned wafers to make sure that the CMP process removes the required materials with no defectivity or dishing/erosion issues. For this analysis techniques like high resolution profilometry (HRP), defectivity analysis, resistivity and ellipsometry, scanning electron microscopy (SEM) and atomic force microscopy (AFM) can be used.
Type of project: Thesis, Internship, Combination of internship and thesis
Duration: at least 3 months
Required degree: Master of Science, Master of Engineering Science, Master of Engineering Technology
Required background: Chemistry/Chemical Engineering, Materials Engineering, Nanoscience & Nanotechnology
Supervising scientist(s): For further information or for application, please contact: Lieve Teugels (Lieve.Teugels@imec.be)