Adaptive-angle scanning method for 3D measurement with atomic force microscopy

Abstract

Three-dimensional atomic force microscopy (3D-AFM) plays a critical role in true 3D measurement, which is potentially required in the manufacture of integrated circuits and in materials science. However, obtaining a 3D profile from a single scan is still a challenge because the probe has to be adjusted to a proper state to measure unknown features. So 3D-AFM is usually time consuming due to repeated scanning in the same area. Here we propose a new scanning strategy, called adaptive-angle scanning, in which the approaching angle of the probe is updated to an appropriate value according to the local surface gradient that is estimated in real time. Meanwhile, the fast scan direction is switched between the y -axis and the z-axis to realize the measurement of top-bottom features and sidewalls. This method is incorporated in a homemade 3D-AFM system to demonstrate its application. Two feedback loops, one integrated in the AFM head and the other under the sample stage, are responsible for changing the approach angle. Experiments are carried out on some standard samples with a tailored CD probe. The 3D-AFM system performs with excellent repeatability on the measurement of the line structure. There is no obvious tip wear observed after continuously scanning 20 times, and the obtained 3D images validate well the method's capability of measuring different structures.

True 3D Nanometrology: 3D-Probing with a Cantilever-Based Sensor

“…The CD AFM and tilting-AFM are oftentimes called three-dimensional (3D) AFMs but have no true 3D-sensing capabilities, mainly because of limitations in cantilever mechanics, which are explained in [ 10 ]. Several approaches to, and developments in, true 3D-sensing or true 3D-AFMs have been made [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ] with promising results. Unfortunately, most of the systems are still under development.…”

Orientation Identification of the Black Phosphorus with Different Thickness Based on B2g Mode Using a Micro-Raman Spectroscope under a Nonanalyzer Configuration

“…Regarding the crystalline orientation of 2D materials, there are several methods, such as microscopic observation using a scanning probe microscope (SPM) [ 23 ] or transmission electron microscope (TEM) [ 24 , 25 ], infrared or micro-Raman spectroscopy, and angle-resolved conductivity. In comparison, the contact method of angle-resolved conductivity has a lower spatial resolution and worse sensitive angle resolution [ 21 ].…”

Crystalline Orientation Identification of Multilayer Black Phosphorus Based on the Ag1 and Ag2 Raman Modes for an Orthogonally Polarized Configuration

“…Among them, angle-resolved conductivity is a contact method . Microscopic methods, based on TEM , or SPM, identify the crystalline orientations of 2D materials mainly by observing high-resolution images and face difficulty in realizing nondestructive, online, and quantitative measurements. In addition, neither the spectral nor the spatial resolution of infrared spectroscopy is enough to match the requirement of crystalline orientation identification for black phosphorus or phosphorene samples at the microscale. , Optical contrast can also be used to identify crystalline orientation, but this method requires measuring the intensity of reflected light from the sample and the substrate, so the substrate also needs to be able to reflect light .…”