Nanolithography is the branch of nanotechnology concerned with the study and application of fabricating nanometer-scale structures, meaning patterns with at least one lateral dimension between 1 and 1,000 nm. As of 2015, nanolithography is a very active area of research in academia and in industry. Optical lithography, which has been the predominant patterning technique since the advent types of lithography pdf the semiconductor age, is capable of producing sub-100-nm patterns with the use of very short optical wavelengths. Multiple patterning is a method of increasing the resolution by printing features in between pre-printed features on the same layer by etching or creating sidewall spacers, and has been used in commercial production of microprocessors since the 32 nm process node e.
By changing the solubility of the resist and subsequent selective removal of material by immersion in a solvent, sub-10 nm resolutions have been achieved. Multiple-electron beam approaches have as a goal an increase of throughput for semiconductor mass-production. Step-and-Flash Imprint Lithography, LISA and LADI are promising nanopattern replication technologies where patterns are created by mechanical deformation of imprint resist, typically a monomer or polymer formulation that is cured by heat or UV light during imprinting.
This technique can be combined with contact printing and cold welding. Dip-pen nanolithography is an additive, diffusive method, thermochemical nanolithography triggers chemical reactions, thermal scanning probe lithography creates 3D surfaces from polymers, and local oxidation nanolithography employs a local oxidation reaction for patterning purposes. 20 nm wide in large pre-patterned trenches has been demonstrated. The degree of dimension and orientation control as well as prevention of lamella merging still need to be addressed for this to be an effective patterning technique.
The important issue of line edge roughness is also highlighted by this technique. Self-assembled ripple patterns and dot arrays formed by low-energy ion-beam sputtering are another emerging form of bottom-up lithography. Aligned arrays of plasmonic and magnetic wires and nanoparticles are deposited on these templates via oblique evaporation. The templates are easily produced over large areas with periods down to 25 nm.
Stencil lithography is a resist-less and parallel method of fabricating nanometer scale patterns using nanometer-size apertures as shadow-masks. X-ray lithography can be extended to a resolution of 15 nm by using the X-ray wavelengths of 1 nm as illumination. This is implemented by the proximity printing approach.