nanopatterning

Nanopatterning refers to techniques that create patterns with features on the nanometer scale, typically below 100 to 200 nanometers, though some methods routinely produce features down to a few nanometers. It is used to modify physical properties such as electrical conductivity, optical response, chemical reactivity, and wettability by controlling surface geometry and composition.

Nanopatterning methods are broadly categorized into top-down and bottom-up approaches. Top-down methods start from a bulk material and selectively remove or modify material to form patterns. Common top-down techniques include electron-beam lithography, photolithography with deep ultraviolet or extreme ultraviolet light, nanoimprint lithography, focused ion beam milling, and interference lithography. Bottom-up methods rely on the self-assembly of nanoscale units, such as block copolymers, colloidal nanoparticles, or molecular building blocks, to arrange patterns spontaneously or under directed assembly conditions.

Pattern transfer is typically achieved by patterning a resist or a mask and then etching or depositing material to embed the pattern into a substrate. This can be followed by lift-off, etch back, or selective deposition. Resolution, throughput, and defect control are critical design considerations; high-resolution patterns often trade off with processing speed and cost.

Materials used in nanopatterning include semiconductors (silicon, GaAs), metals, oxides, and polymers. Substrates range from silicon wafers to flexible polymers. Patterned surfaces find use in electronics, photonics, sensors, catalysis, and surface engineering, including anti-reflection coatings, superhydrophobic textures, and biosensing interfaces.

Challenges include defectivity, line-edge roughness, contamination, process integration, and high equipment costs. Metrology and imaging tools such as scanning electron microscopy and atomic force microscopy are used to assess pattern fidelity and dimensions.

Emerging directions aim to improve throughput and scalability, including roll-to-roll nanoimprint lithography, directed self-assembly strategies, and hybrid approaches that combine bottom-up pattern formation with top-down control.