High-resolution silicon patterning with self-assembled monolayer resists

Single crystal and polycrystalline silicon films have been patterned and etched with a novel high-selectivity process using self-assembled monolayer resists of octadecylsiloxanes (ODS). The highest resolution patterning of sub-10 nm features has been demonstrated by scanning force microscopy imaging of ODS layers patterned with a focused electron beam. An all-dry UV/ozone developer has been used to remove residual carbon from the electron beam exposed regions to improve etch selectivity. The positive tone pattern transfer process consisted of a short buffered hydrofluoric acid wet etch to remove the silicon native oxide followed by a high-selectivity, low ion energy etch using Cl₂ and BCl₃ in an electron cyclotron resonance reactive ion etch. Features have been etched up to 90 nm deep into Si(100) wafers and minimum feature sizes obtained are ∼25 nm. Poly-Si films on SiO₂ insulator layers have been similarly patterned and have been used in a combined process with photolithographic definition of microbridges to form narrow conducting channels in the poly-Si.