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Journal of Nanomaterials
Volume 2015 (2015), Article ID 936876, 7 pages
Research Article

Characterization of Line Nanopatterns on Positive Photoresist Produced by Scanning Near-Field Optical Microscope

1Department of Electrical and Computer Engineering, Florida International University, Miami, FL 33174, USA
2Department of Electrical Engineering, Sharif University of Technology, Azadi Avenue, Tehran 11155-9363, Iran

Received 6 August 2015; Revised 15 September 2015; Accepted 16 September 2015

Academic Editor: Xiaosheng Fang

Copyright © 2015 Sadegh Mehdi Aghaei et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Line nanopatterns are produced on the positive photoresist by scanning near-field optical microscope (SNOM). A laser diode with a wavelength of 450 nm and a power of 250 mW as the light source and an aluminum coated nanoprobe with a 70 nm aperture at the tip apex have been employed. A neutral density filter has been used to control the exposure power of the photoresist. It is found that the changes induced by light in the photoresist can be detected by in situ shear force microscopy (ShFM), before the development of the photoresist. Scanning electron microscope (SEM) images of the developed photoresist have been used to optimize the scanning speed and the power required for exposure, in order to minimize the final line width. It is shown that nanometric lines with a minimum width of 33 nm can be achieved with a scanning speed of 75 µm/s and a laser power of 113 mW. It is also revealed that the overexposure of the photoresist by continuous wave laser generated heat can be prevented by means of proper photoresist selection. In addition, the effects of multiple exposures of nanopatterns on their width and depth are investigated.