Increasingly complex 3D shapes are used as Semicon devices, requiring advanced metrology techniques to monitor production and understand performance of the devices. Atomic force microscopy allows to reach the required sub-nm accuracy by using relatively blunt probes, sensing always in the same direction, but only the top of the 3D shapes can be explored. This project aims to enable the use of nanotube-based probes to scan the profile on the samples with more challenging topographies. The nanotube probe shape strongly improves how well holes or trenches in the sample can be accessed. However, the slender probes become weaker in lateral direction, while sensitivity in this direction is also needed to thoroughly scan the samples.
This PhD position aims to understand the nonlinear dynamics that drive the probe motion in the neighbourhood of high-aspect ratio sample structures. In particular, van der Waals-type attractive forces, electrostatic forces and squeeze-film damping forces will bring a strongly nonlinear force-position dependency, which, in contrast to conventional approaches, cannot be understood by a spherical tip & flat surface approximation. Hence, a 3D force model of the probe tip in the vicinity of the sample will be developed.
Based on the dynamical analysis derived from this force model, a two-dimensional sensing capacity will be developed where profile information can be obtained in longitudinal as well as in lateral direction of the nanotube probe. Hence, sideways bending and buckling of the narrow probe will be also be considered. Experimental validation of the 2D profile sensing is foreseen. The PhD Candidate will be partially located at TNO Optomechatronics, Delft and partially at the TU/e Dynamics and Control group.
Do you recognize yourself in this profile and would you like to know more about the position? Please contact prof.dr. Henk Nijmeijer, H.nijmeijer[at]tue.nl or dr. Hamed Sadeghian Marnani, h.sadeghian.marnani[at]tue.nl or prof.dr.ir. Nathan van de Wouw, N.v.d.Wouw[at]tue.nl.
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