Linewidth Measurement Based on Automatically Matched and Stitched AFM Images

The emergence of ultra-sharp carbon nanotube (CNT) tips provides a new approach to minimize the distortion of the measured linewidth profile caused by interaction with the finite probe tip size. However, the inevitable tilt angle resulting from attaching the nanotube to an ordinary probe causes a significant probe-related distortion on one sidewall of the linewidth sample. In order to obtain accurate images at both sidewalls, the sample is measured twice. After the first measurement which provides an accurate image on one sidewall, the sample is rotated 180 deg to measure the other sidewall. The two images are stitched together as a composite image in which both sidewall images are minimally distorted. To accurately stitch the two images, their position difference caused by the 180 deg rotation must be eliminated. In this paper, the template matching method is adopted after the primary image processing that includes surface leveling and rotation. At the optimum matching position, these two images are stitched as a composite image, in which the average linewidth and the standard deviation are calculated.