Towards a traceable probe calibration method for white light interference based AFM

Probe calibration is the basis of accurate atomic force microscope (AFM) measurement. In white light interference based AFM (WLI-AFM), the relationship between the vertical displacement of probe and the position of the interference fringes on probe cantilever should be calibrated for accurate measurement. In this paper, a traceable probe calibration method for WLI-AFM is proposed. A high resolution displacement measurement system based on laser interference is constructed to obtain the vertical displacement of probe with high accuracy. This system is used for standard displacement input for calibration and makes the measurement result traceable to optical wavelength. A zero-order fringe positioning algorithm is presented to determine the position of the interference fringes on probe cantilever. A probe deflection model is established for the calibration relationship which is continuous and can be used for measurement. While calibration is conducted, series of zero-order fringe positions are obtained corresponding to the probe displacement inputs. The data are processed by the probe deflection model to obtain the calibration relationship. The proposed method is applied in a self-developed WLI-AFM. It is verified that the accuracy of the method is higher than the previous methods by certain experiments on this WLI-AFM.