Next-generation Lithography

Next-generation lithography (NGL) is a term used in integrated circuit manufacturing to describe the lithography technologies slated to replace photolithography. As of 2009 the most advanced form of photolithography is immersion lithography, in which water is used as an immersion medium for the final lens. It is being applied to the 45 nm and 32 nm nodes. Several companies, including IBM, Intel and TSMC, have prepared for the continued use of current lithography, using double patterning, for the 22 nm and 16 nm nodes, and extending double patterning beyond 11 nm.

Candidates for next-generation lithography include: extreme ultraviolet lithography (EUV-lithography), X-ray lithography, electron beam lithography, focused ion beam lithography, and nanoimprint lithography. Electron beam lithography was most popular during the 1970s, but was replaced in popularity by X-ray lithography during the 1980s and early 1990s, and then by EUV lithography from the mid-1990s to the mid-2000s. Focused ion beam lithography has carved a niche for itself in the area of defect repair. Nanoimprint's popularity is rising, and is positioned to succeed EUV as the most popular choice for next-generation lithography, due to its inherent simplicity and low cost of operation as well as its success in the LED, hard-disk and microfluidics sectors.

The rise and fall in popularity of each NGL candidate largely hinged on its throughput capability and its cost of operation and implementation. Electron beam and nanoimprint lithography are limited mainly by the throughput, while EUV and X-ray lithography are limited by implementation and operation costs. 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.

Ironically, each NGL candidate faced more competition from the extension of photolithography than from any other NGL candidate, as more and more methods of improving photolithography continued to be developed, including optical proximity correction, off-axis illumination, phase-shift masks, liquid immersion lithography, and double patterning. Even within the area of photolithography, there is a list of "next-generation" techniques, including two-photon lithography, 157 nm wavelength, and high-index immersion.