Scanning probe lithography

Scanning probe lithography (SPL) describes a set of nanolithographic methods to pattern material on the nanoscale using scanning probes. It is a direct-write, mask-less approach which bypasses the diffraction limit and can reach resolutions below 10 nm. It is considered an alternative lithographic technology often used in academic and research environments. The term scanning probe lithography was coined after the first patterning experiments with scanning probe microscopes (SPM) in the late 1980s.

The different approaches towards SPL can be classified by their goal to either add or remove material, by the general nature of the process either chemical or physical, or according to the driving mechanisms of the probe-surface interaction used in the patterning process: mechanical, thermal, diffusive and electrical.

Mechanical scanning probe lithography (m-SPL) is a nanomachining or nano-scratchingtop-down approach without the application of heat. Thermo-mechanical SPL applies heat together with a mechanical force, e.g. indenting of polymers in the Millipede memory.

Thermal scanning probe lithography (t-SPL) uses a heatable scanning probe in order to efficiently remove material from a surface without the application of significant mechanical forces. The patterning depth can be controlled to create high-resolution 3D structures.

Thermochemical scanning probe lithography (tc-SPL) or thermochemical nanolithography (TCNL) employs the scanning probe tips to induce thermally activated chemical reactions to change the chemical functionality or the phase of surfaces. Such thermally activated reactions have been shown in proteins,organic semiconductors,electroluminescent conjugated polymers, and nanoribbon resistors. Furthermore, deprotection of functional groups (sometimes involving a temperature gradients), reduction of oxides, and the crystallization of piezoelectric/ferroelectric ceramics has been demonstrated.

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