Many technologies once termed "next generation" have entered commercial production, and open-air photolithography, with visible light projected through hand-drawn photomasks, has gradually progressed to deep-UV immersion lithography using optical proximity correction, inverse lithography technology, off-axis illumination, phase-shift masks, double patterning, and multiple patterning.
The rise and fall in popularity of each NGL candidate has largely hinged on its throughput capability and its cost of operation and implementation.
The projection of charged particles (ions or electrons) through stencil masks was also popularly considered in the early 2000s but eventually fell victim to both low throughput and implementation difficulties.
Next generation lithography also generally makes use of ionizing radiation, leading to secondary electrons which can limit resolution to effectively > 20 nm.
[5] The above-mentioned competition between NGL and the recurring extension of photolithography, where the latter consistently wins, may be more a strategic than a technical matter.
This becomes more clear when considering that each resolution enhancement technique applied to photolithography generally extends the capability by only one or two generations.