Method for lateral calibration of Scanning Probe Microscopes based on two dimensional transfer standards

摘要

We describe a method for lateral calibration of a metrology atomic force microscope (AFM), with capacitive sensors, over a scan area of 50 μm×6.25 μm. Using the calibrated microscope we can achieve an expanded uncertainty of U_(L)=0.15% (k=2) for, e.g., the line spacing L of a specimen with a nominal line spacing of 700 nm. The calibration is based on a two dimensional grid, fabricated by a holographic technique, with a reference values of the spacing of ≈0,9 μm and a reference angle between the pitches. A linear transformation of the scanned and uncorrected image into a corrected image can be defined by a correction parameter C_(x) for the x-direction, a correction parameter C_(y) for the y-direction and the angle between the scanned x and scanned y axis. Exact expression for these correction parameters are given for an oblique reference grid. The calibration procedure, measurement procedure and uncertainty evaluation are general.