Executive Summary : | Semiconductor manufacturing involves fabrication of nanoscale electronic devices of various materials stacked in multiple layers. The quality control in the fabrication process involves metrology and defect identification of not only the surface features but also of those buried underneath. Scanning probe microscopy is a uniquely versatile technique employed for in-situ characterization of topography and material properties with sub-nanometer resolution. It further enables non-destructive characterization of sub-surface features in diverse materials including semiconductors. This is done by measuring the contact stiffness between the scanning probe and a sample material, that has been observed to be dependent on the properties and dimensions of the buried features in the vicinity. This project proposes a novel actuation system for the probe in scanning probe microscopy to improve its performance in sub-surface characterization. The actuation system is based on a multi-axis magnetic actuator integrated onto the probe. The proposed system is linear, has a wide bandwidth and achieves collocated multi-axis actuation. Therefore, it enables quasi-static and dynamic characterization of stiffness at the probe-sample interface, along both normal and shear directions. In this project, the interaction between the probe and the sample would be modelled and used for the design of the actuation system. Subsequently, the actuation system would be developed in-house, and characterized using an optical measurement system. The complete system would be demonstrated for the measurement of quasi-static contact stiffnesses and to characterize the dynamics of probe-sample interaction. Experiments would be conducted on various materials and their results would be compared with those from the theoretical model. |