A position-controllable external stage for critical dimension measurements via low-noise atomic force microscopy

An independent external stage for low noise atomic force microscope has been developed for mid-range movements so that it aids in measurements of critical dimensions through the low-noise atomic force microscope. The maximum travel length of the external four-axes stage is 10 mm. For image scanning of the specific target region, the sample needs to be moved through two steps: coarse positioning with the external stage and fine positioning with PI XY piezo scanner. Prior to the CD measurements, we confirmed that the position errors caused by the external stage and tip stage were negligible through the reproducibility experiments. In this study, custom-designed software stored the initial position of the probe and then moved it precisely to the sample location to be measured. Subsequently, the sidewalls of an improved vertical parallel structure were measured and the repeatability and reproducibility of the CD measurements were estimated using a CDR30-EBD tip. Finally, we confirmed that tip wear could be minimized by measuring TGX1 samples with undercut structures.