Sub-20 nm silicon patterning and metal lift-off using thermal scanning probe lithography

Abstract

The most direct definition of a patterning process' resolution is the smallest half-pitch feature it is capable of transferring onto the substrate. Here we demonstrate that thermal Scanning Probe Lithography (t-SPL) is capable of fabricating dense line patterns in silicon and metal lift-off features at sub 20 nm feature size. The dense silicon lines were written at a half pitch of 18.3 nm to a depth of 5 nm into a 9 nm polyphthalaldehyde thermal imaging layer by t-SPL. For processing we used a three-layer stack comprising an evaporated SiO 2 hardmask which is just 2-3 nm thick. The hardmask is used to amplify the pattern into a 50 nm thick polymeric transfer layer. The transfer layer subsequently serves as an etch mask for transfer into silicon to a depth of ≈ 65 nm. The line edge roughness (3 σ) was evaluated to be less than 3 nm both in the transfer layer and in silicon. We also demonstrate that a similar three-layer stack can be used for metal lift-off of high resolution patterns. A device application is demonstrated by fabricating 50 nm half pitch dense nickel contacts to an InAs nanowire.

Tipping solutions: emerging 3D nano-fabrication/ -imaging technologies

“…The smallest half-pitch feature of ~18 nm for a pattern transfer into Si for up to 65-nmdeep trenches which only have an edge roughness of 3 nm [130,131].…”

Thermal scanning probe lithography—a review

“…f A functional layer under the temperature-sensitive resist can be locally accessed when the resist is removed and simultaneously activated by the thermal probe [70][71][72] or in a subsequent step by oxygen plasma 73 . g A three-layer stack composed of a temperature-sensitive resist, a thin inorganic hard mask and an organic transfer layer is suitable for high aspect ratio and high-resolution etching 29,43,69,[74][75][76] . h The three-layer stack can also be used for a high-resolution liftoff processes 76,77 Cinnamate…”

Emerging Scanning Probe–Based Setups for Advanced Nanoelectronic Research

“…The process of patterns' formation mainly relies on the strong contact force between the tip and the sample . ii) Thermal SPL (t‐SPL) : this technique uses a heating probe to alter the properties of the sample locally . iii) Thermochemical SPL (tc‐SPL) : this technique modifies the chemical properties of a material locally by heating; iv) Dip pen SPL (dp‐SPL) : this technique allows depositing of various types of molecules or inks on the surface of the samples .…”