Atomic force microscopy using beam fabricated tips: resolution issues

A question often arises concerning the resolving power of the AFM compared with that of the scanning electron microscopy (SEM). One of the advantages of AFM is that it gives accurate three dimensional topographic information that the SEM can not provide. Figure 1(a) shows an SEM micrograph of a two level metal integrated circuit with intermetalic dielectric (unpassivated) that has a complicated three dimensional structure. Quantitive feature height information can not be obtained from this picture. But, as shown in Figure 1(b) die AFM perspective image clearly gives us the details of three dimensional information. In Figure 1(c), a line scan taken from the image yields the height of the pattern quantitively. However, the image we obtain with an AFM is often complicated by the nature of the sample and the structure of the tip. If the dimension of the tip is larger than the topography of the sample, the image will reflect the shape of die tip, which is one of die problems associated with pyramidal shapes of commercial AFM tips (5.0 Х 5.0 μm square base and 55° slope of sidewalls).