Schwarzschild-objective-based EUV micro-exposure tool

摘要

Diffraction limited 20x Schwarzschild objectives have been fabricated for various applications at 13.5nm wavelength. For this purpose the major parts of the whole technology chain for the realization of diffraction limited reflective optical systems working in the EUV spectral region have been established. This chain includes: optical design of the system, mechanical construction of mounting structures on the basis of extensive stress and thermal analysis, development of adhesive free mountings, high-reflective Mo/Si multilayer coatings for use at 13.5nm wavelength, assembly of the whole objective system, development of adapted semiconductor detectors for 13.5nm. The realized Schwarzschild objectives with a numerical aperture of NA=0.2 have been integrated into different optical set-ups such as a table top scanning micro exposure tool and an EUV microscope. The EUV micro exposure tool is currently used for various EUVL-related applications such as investigations of resolution limiting factors and EUV resist sensitivity test stand. Properties and performance of both the Schwarzschild objective and the optical set-up are presented in the paper.