Optics 'beyond EUV' proposal granted
31 January 2008
Within the STW Thin Film Nanomanufacturing program, a 4-year research project on multilayer optics 'beyond EUV' has been granted to FOM and the Solid State Physics/MESA+ Institute at the University of Twente.
Current reflective optics, based on Bragg reflection of EUV (13.5 nm) radiation, have enabled the development of high-resolution lithography for the manufacturing of integrated circuits. Prototypes build by ASML and Carl Zeiss SMT, of which half of the optics were coated by FOM, demonstrated chip patterns with sizes down to 32 nm. However, the ever increasing resolution demands require the industry to continuously find ways to even further improve the resolution. An obvious solution is to again reduce the wavelength. Though the lithography target of 6.7 nm is 'only' a factor of two reduction in wavelength, this represents a dramatic step in coating technology. The individual layer thicknesses in the multilayer become of the same scale as the natural layer and interface imperfections, limiting the multilayer performance severely.
The 'beyond-EUV' optics will need to have atomically sharp optical index profiles, full chemical and thermal stability, and a high radiation damage resistance. This requires a fundamentally different approach. Research on three new issues will be carried out: two ways of growing atomically smooth and closed layers as well as a technique to stabilize the layer interfaces. Furthermore a new type of microscopy with sub-nanometer element specific depth resolution will be used to study the interfaces.
The goal is to develop these techniques to deliver near-theoretical results for the wavelength range beyond the EUV.
The M€1.3 project is supported by Carl Zeiss SMT and is carried out in collaboration with the Solid State Physics/MESA+ Institute at the University of Twente.