Batch fabrication of AFM probes with direct positioning capability

Abstract

One major problem for most commercial atomic force microscope (AFM) probes is the uncertainty of the tip location relative to its cantilever. In most scenarios, AFM probes have tips 5–25 μm away from the very end of the cantilever, and it is thus impossible to know where exactly the tip is because the camera in an AFM system shows only the backside of the AFM cantilever. This uncertainty of the tip location has raised some major problems, e.g., the initial scanning area must be set very large to ensure that the area of interest is within the scanning field. Here, the authors will show a straightforward fabrication method that can convert a wafer of regular pyramidal-shaped probes into direct positioning probes, for which the tip is located either at the very end of its cantilever or next to a through-cantilever hole that is visible when viewed from the backside of the cantilever. Our method involves angle evaporation of a hard mask layer onto the AFM probe, followed by dry etching of silicon that etches the area not covered by the metal layer, i.e., the shadow area of the pyramid-shaped tip. As an additional benefit, because our process etched away half of the tip pyramid, the resulting tip is sharper with a smaller half cone angle than the original one, leading to higher resolution imaging.