Optical Lithography: 100 nm and Beyond.
Article on page 78, September '98 Semiconductor International:
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The debate over which non-optical technique will carry the industry beyond 100 nm continues with increased complexity. With developments in the optical arena in deep UV photoresists and high NA lithography tools, research groups are reporting similar results to non-optical methods - critical dimensions (CD) of 60 to 80 nm. Therefore, in addition to X-ray, ion projection, SCALPEL and extreme UV, optical lithography can be added to the list of "alternative" lithography technologies.
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Optical and non-optical techniques have produced similar sub-100 nm proof-of-concept results, and while optical lithography is mature, both need to build and strengthen the necessary infrastructures. With four non-optical and three optical wavelength options, a practical production solution at the 130 nm technology node is still a long way off. For optical, the current environment of cooperation can aid in the effort to integrate all lithography components and extend usefulness to smaller features. Though speculation about the end of optical lithography has persisted for the past 25 years (Fig. 4), Sturtevant believes that with 157 nm lithography, optical methods may extend to the year 2015.
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The three optical options discussed are 193 nm chemistries (including the U of Texas / DPMI results), extending 248 nm technology, and bilayer resists. Figure 4 is an interesting plot showing consensus 'Projected end of optical lithography', 1976 to present with extrapolation [Source: Motorola]:
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