Investigation of fabrication parameters for the electron-beam-induced deposition of contamination tips used in atomic force microscopy

Electron-beam deposition in a field-emission electron microscope is used to grow high aspect ratio carbon contamination tips suitable for imaging in atomic force microscopy. Tip lengths of up to several microns, tip diameters between 100 and 400 nm and cone half-angles of 3 degrees -50 degrees are achieved with typical radii of curvature between 20 and 40 nm. The influence of the major deposition parameters, i.e. electron energy, beam current, deposition time and working distance, on the growth rate and shape (length, cone angle and cone length) of the tip, are investigated systematically. It is found that increasing beam current leads to a decrease in length growth probably due to enhanced thermal desorption of adsorbates and reduced sticking coefficients. Electron energy mainly determines cone angles and cone length while the variation of working distance only has a small influence on the tip growth. Imaging capabilities of the tips are verified on vertically walled, lithographically fabricated patterns.