Maskless lithography (MPL) is a photomask-less photolithography-like technology used to project or focal-spot write the image pattern onto a chemical resist-coated substrate (e.g. wafer) by means of UV radiation or electron beam.
[1] In microlithography, typically UV radiation casts an image of a time constant mask onto a photosensitive emulsion (or photoresist).
[2] Traditionally, mask aligners, steppers, scanners, and other kinds of non-optical techniques are used for high speed microfabrication of microstructures, but in case of MPL, some of these become redundant.
Also combinations of the two approaches are known, and it is not limited to optical radiation, but also extends into the UV, includes electron-beams and also mechanical or thermal ablation via MEMS devices.
Also the digital throughput of such systems forms a bottleneck for high resolutions, i.e. structuring a 300mm diameter wafer with its area of ~707cm² requires about 10 TiB of data in a rasterized format without oversampling and thus suffers from step-artefacts (aliasing).
Oversampling by a factor of 10 to reduce these artefacts adds another two orders of magnitude 1 PiB per single wafer that has to be transferred in ~1 min to the substrate to achieve high volume manufacturing speeds.
In addition, focused ion beam (FIB) systems have established an important niche role in failure analysis and defect repair.
Direct laser writing is a very popular form of optical maskless lithography, which offers flexibility, ease of use, and cost effectiveness in R&D processing (small batch production).
The underlying technology uses spatial light modulating (SLM) micro-arrays based on glass to block laser pathway from reaching a substrate with a photoresist (in similar manner to digital micromirror devices).
[6] The MCC system was fully integrated with precision control for 3D surfaces and artificial intelligence software with real-time machine learning and included laser wavelengths for standard i-line resist and DUV 248nm.
The main optical maskless lithography systems in use today are the ones developed for generating photomasks for the semiconductor and LCD industries.
Even within the electron-beam category, there are several vendors (Multibeam, Mapper Lithography, Canon, Advantest, Nuflare, JEOL) with entirely different architectures and beam energies.