Delivered by Ingenta to: McMaster University IP: 5.62.157.96 On: Sun, 19 Jun 2016 10:51:27 Copyright: American Scientific Publishers RESEARCH ARTICLE Copyright © 2011 American Scientiﬁc Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 11, 11041–11044, 2011 Estimation of AFM Tip Shape and Status in Linewidth and Proﬁle Measurement Guoqiang Han 1 2 ∗ , Zhuangde Jiang 2 3 , Weixuan Jing 2 , Philip D. Prewett 3 , and Kyle Jiang 3 1 School of Mechanical Engineering and Automation, Fuzhou University, Fuzhou, Fujian 350108, PR China 2 State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, PR China 3 School of Mechanical Engineering, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK An atomic force microscopy image is a dilation of the specimen surface with the probe tip. Tips wear or are damaged as they are used. And AFM tip shape and position status make AFM images distorted. So it is necessary to characterize AFM tip shape and position parameters so as to recon- struct AFM images. A geometric model-based approach is presented to estimate AFM tip shape and position status by AFM images of test specimens and scanning electron microscope (SEM) images of AFM tip. In this model, the AFM tip is characterized by using a dynamic cone model. The geometric relationship between AFM tip and the sample structure is revealed in linewidth and proﬁle measurement. The method can easily calculate the tip parameters including half-cone angle, installation angle, scanning tilting angle and curvature radius, and easily estimate the position status of AFM tip when AFM tip moves on the specimen. The results of linewidth and proﬁle measurement are amended accurately through this approach. Keywords: Atomic Force Microscopy (AFM), Scanning Electron Microscope (SEM), Tip Characterization, Linewidth and Proﬁle Measurement. 1. INTRODUCTION With the development of the IC technology and MEMS devices, more and more AFMs and AFM proﬁlers will be used to qualify micro/nano structures and the requirement of the accurate 3D measurement is increasing. 1 2 For mea- surement of linewidth (CD), particle shape, surface rough- ness and the shape of structures in the micrometer and nanometer range, the tip shape has a signiﬁcant effect on the measured proﬁles and makes AFM image distorted. So AFM tip and image need to be reconstructed. 2–7 In the case of AFM, since the scanning probe physically interacts with the structure of interest at a close proximity, often the interaction between the AFM tip and the sample leads to a variation of the tip shape and status (such as the scanning tilting angle of AFM tip). Nowadays the uncertainties for linewidth and proﬁle measurement are in the nanometer or picometer range. 3 4 To determine the true morphology of a sample in linewidth and proﬁle measurement, it is nec- essary to know the tip shape or, more correctly, the effect of the tip shape on the AFM images. Usually the dimen- sion and shape of the cantilever tip are measured with the help of microphotographs obtained by scanning electron ∗ Author to whom correspondence should be addressed. microscopes (SEM), but this method will probably make AFM tip destructed or contaminated. To solve this prob- lem, special test structures are used as probe characterizers in situ. 7–13 These test structures may be natural (natural or artiﬁcial crystals are usually used) or specially created through micro/nano fabrication techniques. Several math- ematic and blind estimation methods 14–18 of SPM tip were presented, but these methods are not perfect enough and have their limitations because of AFM image noise effects. In this paper, an AFM tip characterizer was tested to estimate the AFM tip shape and status as the probe tip moves on the samples. The purpose of the present work is the representation of a method and algorithms to esti- mate the AFM tip shape and position status. AFM images are distorted representations of sample surfaces and shapes due to the dilation produced by the ﬁnite size and status of the tip in micro/nano-scale linewidth and proﬁle measure- ment. It is necessary to obtain the tip shape and status in order to correct such distortion in micro/nano metrology. 2. METROLOGICAL METHOD The metrological method is based on the AFM measure- ment of a sharp-edge line-space structure and the calcu- lation of the tip shape from the measurement results. On J. Nanosci. Nanotechnol. 2011, Vol. 11, No. 12 1533-4880/2011/11/11041/004 doi:10.1166/jnn.2011.4032 11041