Carbon nanotube tips for scanning probe microscopy: fabrication and high aspect ratio nanometrology

The atomic force microscope (AFM) is being adapted by industry as a tool for in line fabrication metrology. The last two decades have witnessed the evolution of the AFM into a versatile instrument, with many new scanning force techniques presently being developed. Consequently, the AFM has wide industrial applications from conventional surface roughness measurement of thin films to the characterization of magnetic domains as related to the information storage industry. There are a number of challenges that must be resolved in order to fully realize the potential of AFM as future nanoscale inspection tools for the information technology industry. Improvement in AFM tip technology is one of the most important factors for AFM to be fully adapted by industry. This paper reviews the development and application of carbon nanotube AFM tips, highlighting the progress from our lab. Many applications for carbon nanotube AFM tips have been demonstrated for scanning probe microscopy; however, herein we focus mainly on the measurement of high aspect ratio nanostructures. The structure of carbon nanotubes will be described in relationship to the application of the AFM tip. Fabrication techniques for carbon nanotube AFM probes will be highlighted, including an example detailing a high throughput large-scale production method. Data demonstrating the capability of carbon nanotube tips for imaging high aspect ratio features will be compared with conventional top-down SEM metrology. This review will also address some of the technical challenges that still remain for the full implementation of carbon nanotube AFM tip technology for industrial applications.