Proximity effects in nanoscale patterning with high resolution electron beam induced deposition

Electron beam induced deposition can be used to deposit dots as small as 1 nm on planar substrates. However, more complex patterns composed of arrays of closely space dots may be distorted because of proximity effects arising from the fundamental nature of secondary electron generation. These proximity effects are investigated by exploring the visibility of nanoscale letters fabricated by dissociating a Pt organometallic precursor onto a Si3 N4 substrate. The pattern visibility and deposited mass distribution have been investigated for letters with widths of 5-20 nm. Letter visibility is very good down to 10 nm but the pattern is completely obscured by 5 nm. Moreover, the deposited mass distribution for 5 nm width letters bears almost no resemblance to the pattern traced by the primary electron beam. The mass distribution for the component dots employed here has a Lorentzian distribution with a full width at half maximum of 2.3 nm. The overlap in the tails of the Lorentzian contributes to a reduction in the visibility of the 10 nm sized letters. However, for patterns formed with dots separated by less than 2 nm, additional electrons are emitted from previously deposited nearby regions, substantially destroying the pattern for letters of width equal to 5 nm.