A 3D surface nanomechanical property mapping method with a magnetic-drive orthogonal cantilever probe.

Traditional force-distance curve based atomic force microscopy (FD-AFM) is limited to two-dimensional (2D) surface characterization, making the in situ mapping of three-dimensional (3D) surface nanomechanical properties (SNMP) challenging. This paper presents a multimode 3D FD-AFM based on a magnetic-drive orthogonal cantilever probe (MD-OCP) that can achieve SNMP imaging of 3D micro-nano structures with surface contour fluctuations reaching or exceeding several microns. Bending, torsion and vector tracking modes are integrated into this method for a 2D horizontal surface, 2D sidewall, and 3D surface mapping, respectively. The MD-OCP consists of a horizontal cantilever, a vertical cantilever with a protruding tip, and a magnetized bead. It can be utilized in the detection of deep trench and dense microarray units. The force analysis during 3D SNMP measurement is performed through mathematical derivation, which shows a clear relationship between effective indentation force, friction, and total tip-sample interactions. Single-point SNMP evaluation, discrete 2D SNMP imaging, and continuous omnidirectional 3D SNMP mapping of a 3D microarray unit verify the accurate and comprehensive measurement abilities of the reported method in its bending, torsion, and vector tracking modes. The experimental results demonstrate that this method can achieve excellent 3D quantitative characterization of topography and SNMP, including critical dimensions, adhesion, Young's modulus, stiffness, and energy dissipation, along a 3D device surface. This novel 3D FD-AFM technique has many potential applications in the further exploration of 3D micro-nano devices.