Feb 19, 2009
Nanofabrication observed in real-time
Conventional nano and microfabrication techniques rely on a patterning process being performed and the sample subsequently imaged to inspect the result of the process. By performing the patterning and imaging simultaneously, defects can be identified immediately and a substantial time saving can be made during the total fabrication cycle. This requires new technology to be developed combining these two attributes and provides a stimulus for the next generation of fabrication tools.
Over the last five years, researchers in the Nanophysics and Soft Matter Group at the University of Bristol, UK, have been developing a novel high-speed atomic force microscope (AFM). Perhaps the most versatile of surface characterization tools, the AFM is capable of nanoscale resolution in three dimensions and can be operated in air, vacuum and under liquid. The high-speed AFM allows video-rate imaging of surfaces to be performed, enabling scientists to observe changes in topography in real-time. A natural progression is the application of the high-speed AFM to nanofabrication.
It has long been known that by applying an electric field between the sharp tip of an AFM and a metallic or semiconducting sample, the surface of the sample can be locally oxidized. For this work, scientists chose to replicate a common semiconductor fabrication process – the oxidation of silicon. Generation of the silicon oxide patterns was controlled by synchronizing the application of the electric field to the scanning motion of the high-speed AFM. The results, published in Nanotechnology, demonstrate the ability to observe in real-time the patterning of lines of silicon oxide 100 nm wide and less than 2 nm high, as well as larger patterns over areas of several square microns.
This work represents the first step towards new fabrication technology, whereby patterning and inspection can be performed simultaneously. Future developments aim to improve the scanning mechanism of the high-speed AFM and the range of patterning processes that can be implemented.
About the author
Dr James Vicary is a postdoctoral researcher in the Nanophysics and Soft Matter Group at the University of Bristol. This work, from his PhD thesis, was performed under the supervision of Prof. Mervyn Miles, head of the group, and funded by the IRC in Nanotechnology, a collaboration between the universities of Bristol, Cambridge and UCL.