Study of an AFM probe having a cantilever with a longer diamond tip for metrological application

The Atomic Force Microscope (AFM) is a powerful tool in the fields of micro-and nano-metrology for the measurement of surfaces with micro-/nano-structures. However, there are some limitations to the vertical measuring range when the step size of a micro-/nano-structure is bigger than the tip height. The tip height, typically 15 mu m, is defined as the distance from the apex of the tip to the bottom surface of the cantilever. To avoid possible interference between the cantilever and the structures under test, the maximum measuring range is usually set at one-third of the tip height to prevent any damages on the tip/cantilever and the test surface. In addition, the vertical measuring range in a conventional AFM is also limited by its available vertical scanning range, typically less than 10 mu m. As such, a structure with a height or depth of several tens of micrometres cannot be measured by a conventional AFM. To overcome these limitations, a longer tip and larger vertical scanning range in AFM are needed. In this paper, a newly developed long diamond tip up to 65 mu m is mounted on a tipless AFM cantilever and used with a Large Range Metrological AFM (LRM-AFM) which has a vertical scanning range of up to 5 mm with a resolution of 0.1 nm in order to measure structures with deeper groove. Measurements were successfully made on a step height of 24 mu m, and the result obtained is very promising and this can effectively extend the vertical measuring range in nano-scale dimensional calibrations and measurements.