Creating nanostructures on silicon using ion blistering and electron beam lithography

Abstract

We have investigated the patterning of silicon surfaces using ion blistering in conjunctionwith e-beam lithography. Variable width (150–5000 nm) trenches were first written in500 nm thick PMMA resist spin coated on silicon, using an electron beam. Next, 10 keVH2+ ions were implanted to various fluences through the masks. The resistwas then removed and the samples were rapidly thermally annealed at900 °C. The resulting surface morphologies were investigated by atomic force microscopy. In thewider trenches, round blisters with 600–900 nm diameter are observed, which are similar tothose observed on unmasked surfaces. In submicron trenches, there is a transition inmorphology, caused by the proximity to the border. The blisters are smaller and they aredensely aligned along the trench direction (‘string of pearls’ pattern). Unusual blistergeometries are observed in the narrowest trenches (150 nm) at higher H doses(≥1 × 1017 H cm−2)—such as tubular blisters aligned along the trench. It was also found that for H doses of≥6 × 1016 H cm−2 the surface swells uniformly, which has implications for the blistering mechanism. Theprospects for accomplishing ion cutting, layer transfer and bonding of finely delineatedpatterns of silicon onto another material are discussed in the light of the above results.