An image stitching method to eliminate the distortion of the sidewall in linewidth measurement

Nano-scale linewidth measurements are performed in semiconductor manufacturing, the data storage industry, and micro-mechanical engineering. It is well known that the interaction of probe and sample affects the measurement accuracy of linewidth measurements performed with atomic force microscopy (AFM). The emergent ultra-sharp carbon nanotube tips provide a new approach to minimizing the distortion of the measured profile caused by interaction with the finite probe tip. However, there is nearly always a significant tilt angle resulting when the nanotube is attached to an ordinary probe. As a result, we can obtain an accurate sidewall image of only one side of the linewidth sample rather than two sides. This somewhat reduces the advantage of using nanotube probes. To solve this problem, a dual image stitching method based on image registration is proposed in this article. After the first image is obtained, which provides an accurate profile of one side of the measured line, we rotate the sample 180° to obtain the second image, which provides an accurate profile of the other side of the line. We keep the sidewall data for the better side of each image and neglect the data taken for the other side of each image. Then, we combine these better two sides to yield a new image for which the linewidth can be calculated.