Measurement of micro-roughness using a metrological large range scanning force microscope

A new method for traceable measurement of micro-roughness by using a newly developed metrological large range scanning force microscope (LR-SFM) is described. The LR-SFM has an Abbe error free design and direct interferometric position measurement capability, and is capable of measuring samples in a volume of 25 mm x 25 mm x 5 mm along x, y and z axes. The instrumentation and several important design concepts are introduced in this paper. Measurement results of a plane glass and a micro-roughness standard have illustrated that the instrument has a low noise level of R-a = 0.58 nm and good measurement repeatability. Furthermore, a group of comparison measurements on a micro-roughness standard have been carried out between the LR-SFM and a stylus profiler. The obtained roughness values from both instruments are in excellent agreement with each other. This LR-SFM overcomes the difficulty that roughness values measured by conventional SFMs cannot be compared to stylus profilers or interference microscopes, mainly due to the fact that conventional SFMs do not have the required scanning range of ISO standardized evaluation methods.