True 3d nanometrology: 3d‐probing with a cantilever‐based sensor

Abstract

State of the art three‐dimensional atomic force microscopes (3D‐AFM) cannot measure three spatial dimensions separately from each other. A 3D‐AFM‐head with true 3D‐probing capabilities is presented in this paper. It detects the so‐called 3D‐Nanoprobes CD‐tip displacement with a differential interferometer and an optical lever. The 3D‐Nanoprobe was specifically developed for tactile 3D‐probing and is applied for critical dimension (CD) measurements. A calibrated 3D‐Nanoprobe shows a selectivity ratio of 50:1 on average for each of the spatial directions x, y, and z. Typical stiffness values are kx = 1.722 ± 0.083 N/m, ky = 1.511 ± 0.034 N/m, and kz = 1.64 ± 0.16 N/m resulting in a quasi‐isotropic ratio of the stiffness of 1.1:0.9:1.0 in x:y:z, respectively. The probing repeatability of the developed true 3D‐AFM shows a standard deviation of 0.18 nm, 0.31 nm, and 0.83 nm for x, y, and z, respectively. Two CD‐line samples type IVPS100‐PTB, which were perpendicularly mounted to each other, were used to test the performance of the developed true 3D‐AFM: repeatability, long‐term stability, pitch, and line edge roughness and linewidth roughness (LER/LWR), showing promising results.