A large range metrological atomic force microscope and its uncertainty analysis

The atomic force microscope (AFMs) is widely used in nanotechnology research and industry. To ensure the quantity consistency, the measurement precision of these machines must be calibrated and trace back to SI international unit. In the calibration process, first the standard grating pitch artifact is calibrated by metrological atomic force microscope which has the direct tracing capability; then the grating pitch artifact is transferred to calibrate the common AFMs. Because the importance of metrological atomic force microscope in nanometer tracing, the NIM of China has developed a large range metrological atomic force microscope with 50mmx50mmx2mm scan area. In this paper, the structure and performance of this instrument will be introduced briefly. The instrument utilizes a series of novel designs like hybrid air bearing and sliding guide platform, three dimensional orthogonal piezo scanner head, multi-pass interferometer and Fourier harmonic components separation method to achieve both high precision measurement in small area and fast measurement in large area. As a metrological instrument, the error sources and uncertainties of mAFM are also analyzed, theoretical analysis and experiments show the standard uncertainty of the mAFM is less than 2nm in small range and 20nm in large range