Design and characterization of MIKES metrological atomic force microscope

An interferometrically traceable metrological atomic force microscope (IT-MAFM) has been developed at MIKES. It can be used for traceable atomic force microscope (AFM) measurements and for calibration of transfer standards of scanning probe microscopes (SPMs). Sample position is measured online by 3 axes of laser interferometers. A novel and simple method for detection and online correction of the interferometer nonlinearity was developed. Effect of the nonlinearity in measurements is demonstrated. In the design, special attention has been paid to elimination of external disturbances like electric noise, acoustic noise, ambient temperature variations and vibrations. The instrument has been carefully characterized. The largest uncertainty components are caused by Abbe errors, orthogonality errors, drifts and noise. Noise level in Z direction was 0.25 nm, and in X and Y directions 0.36 nm and 0.31 nm, respectively. Standard uncertainties for X, Y and Z coordinates are ucx = q[0.48; 0.04x; 0.17y; 1.7z; 2 time] nm, ucy = q[0.45; 0.31x; 0.07y; 0.14z; 4 time] nm and ucz = q[0.42; 3x; 7.2y; 0.18z; 2 time] nm where x, y, z are in μm and time in h. Standard uncertainty for 300 nm pitch is 0.023 nm,and for 7 nm step height measurement is 0.35 nm. Uncertainty estimates are supported by an international comparison.