Statement of purpose

Extreme-ultraviolet lithography (EUVL) is a leading contender for next-generation lithography in which critical feature sizes will be pushed down to 22 nm and below.  A major obstacle to the introduction of this technology is the deterioration of the optics caused by long-term exposure to the 92 eV photons in a non-bakable vacuum environment.  In order to meet the throughput requirements for high-volume production, the reflectivity of the projection optics must not drop more than a few percent over the entire 30,000-hour lifetime of the printing tool.  To achieve this, in situ methods are being explored to ameliorate the carbonization and oxidation processes induced by the EUV irradiation of the organics and water which adsorb on the optic surfaces from the ambient vacuum.

Key to advancing this effort is a better understanding of both the thermally-driven adsorption physics and the photon-induced processes that contribute to EUV-optics contamination.  Recent results have shown a highly sub-linear (approximately logarithmic) pressure dependence of the contamination rates down to very low pressures.  Since this behavior is not predicted by contamination models such as those based on ideal surfaces and simple Langmuir adsorption, the workshop will address the question of how the experimental and theoretical methods of basic surface science can be employed to more accurately model the steady-state coverage of organic molecules at the very low partial pressures expected in the production environment (below 10-8 Pa).  Another high-interest topic that will be considered is photon-stimulated surface reactions relevant to the carbonization processes and how these processes might be affected by the presence of adsorbed water or other potentially oxidizing species, and how one might exploit the competition between oxidation and carbonization to mitigate or even reverse carbon deposition

The participants will include both experimental and theoretical scientists from academia with a broad expertise and perspective on basic surface science as well as scientists and engineers from the EUVL community working directly on optics contamination, mitigation and fabrication.  There will be equal emphasis on presentations and on guided and open discussions throughout the workshop.

Date and place: June 2, 2009, NIST, Gaithersburg, MD