Deep reactive ion etching and focused ion beam combination for nanotip fabrication

We have studied the fabrication of high-aspect ratio silicon tips by a combination of deep reactive ion etching and focused ion beam. The reactive ion etching is used to obtain so-called “rocket tips” which can be fabricated with a high aspect ratio. The rocket tips are further processed by using a focused ion beam to obtain nanotips at their apex. Typical results obtained are nanotips with a basis radius of 200 nm and a height of 2.5 μm, with an apex radius of 5 nm, located on top of a 3 μm wide and 9 μm high silicon column. The process would allow however obtaining column heights of several tens of microns.