Imaging VLSI cross sections by atomic force microscopy

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Abstract
An application of atomic force microscopy (AFM) to the imaging of VLSI cross sections of metallographically polished samples is reported. AFM is a descendant of scanning tunneling microscopy (STM). Both STM and AFM are part of the rapidly growing field of scanning probe microscopy (SPM), which constructs three-dimensional contour maps of surfaces with up to atomic resolution by probing a variety of different material properties. The SPM technique has been extended in order to image VLSI cross sections as a possible alternative to conventional scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The major advantage of AFM over conventional imaging techniques, such as scanning or transmission electron microscopy, is the higher resolution achievable in combination with higher throughput and the easy access to quantitative data, such as line widths or re-entrant angles. A very good correlation of AFM VLSI cross section images, acquired in air, was observed with those acquired by SEM and TEM.