At the SPIE Advanced Lithography Symposium in February, Ralph Dammel treated us to an update of his 2002 paper “Photoresists for microlithography, or the Red Queen’s race” [J. Microlith., Microfab., Microsyst., Vol. 1 No. 3, October 2002, 270-5]. He measured performance in stepper/scanner technology by NA (at fixed wavelength) and performance in resist technology by an “equivalent NA” (by way of resolution). As was the case up to 2002, lithography progress due to resist performance continues to out pace that due to scanner performance. (The ratio ΔNA(resist) / ΔNA(scanner) lies above 1.) And yet, this investment in hardware remains more than 10 times the corresponding investment in “wetware” (to use Dr. Dammel’s term). The question then is whether the industry has adjusted investment to optimize its return on investment, or have we arrived at this situation by historical accident.
In his 2002 paper, Dr. Dammel made the point that the respective investments were spread over twice as many resist vendors as over stepper/scanner vendors. The limited funding available to any one resist company means that company is unable to fund R&D at an adequate level over the entire life-cycle of a resist system (invention to obsolescence).
What are some possible consequences? First, much of resist materials research and invention now takes place in the university environment instead of in chemical companies or semiconductor industry research labs. That is, the inventors have found supportive environments outside of industry. The onset of economic recession in 2008 has had dramatic impact on university hiring in many countries, so universities may not be home to the next generation of resist chemists.
Second, as we have seen in another critical yet underfunded segment – mask making – the resist manufacturing segment may well consolidate further, with consequent slowing of innovation and reduction of alternatives. Even with the pipeline filled by the researchers, development and scale-up of a resist system is an arduous and expensive proposition, one that needs adequate investment.