Production and characterization of high-aspect-ratio probes for use in resonance-mode AFM

Applications of atomic force microscopy (AFM) for the characterization and metrology of technologically-important objects (e.g. x-ray lithography masks) has led to the development of special-purpose, high-aspect-ratio probes. Measuring objects that have deep, narrow trenches requires a controlled probe geometry. The probe radius and aspect ratio determine the congruence of the acquired AFM image to the true profile of the sample. As is illustrated schematically in Figure 1(a), the usual batch-fabricated AFM probe cannot reach down into deep or narrow trenches. Highaspect- ratio AFM probes that can overcome this limitation (Figure lb), have been developed. Probes of ≤100 nm shaft diameter, and up to microns in length, can be grown by electron-beam contamination writing. Focused ion beams have also been used to sharpen conventional probes by rastering a circular pattern around the highest point, removing the“shoulders” by sputtering, and thereby improving the aspect ratio. Previous work has demonstrated the use of such probes in standard, contact-mode AFM. This paper extends the application of these techniques to the creation of probes for resonance-mode AFM, and characterizes the performance of the resulting probes.