The Research And Characterization Of Cleaning Methods And Smoothing Layer For The Substrate Of Extreme Ultraviolet Multilayer

Multilayer reflective mirrors are widely used in the extreme ultraviolet (EUV) space observation, plasma diagnostic and synchrotron radiation, particularly as a key component in the next EUV lithography. The reflectivity of multilayer marks its research level. In EUV wavelength range, because of the short wavelength in tens nanometer scale, substrate roughness significantly degrades the reflectivity of the multilayer mirrors. It is required to obtain the super-smooth surface substrate with low roughness. And it is an important research subject for high reflectivity multilayer mirrors. On the other hand, the characterization and evaluation of substrate surface is also required for the fabrication of the super-smooth substrate.In the thesis, cleaning theory and methods of super-smooth for silicon and glass substrate were introduced, including swabbing and ultrasonic cleaning technologies. The orthogonal experiment method was designed, and some main factors affected the quality of substrate cleaning were investigated, such as the temperature of clean solution, cleaning time and ultrasonic power and so on. For the swabbing cleaning method, although some contaminant can be removed, some side effect was followed. It is can be found that the cotton fiber results in the abrasive or residual, and the new contaminant was introduced. For the ultrasonic cleaning method, the contaminant was avoided, and the surface roughness reduced to less than 0.2nm. Therefore, the orthogonal experiment method was used to optimize ultrasonic cleaning technology. The experimental results suggest that the ultrasonic temperature has remarkable effect and the results of 35°C and 45°C are better than that of 25°C, however, the ultrasonic time (10min and 20min) has not effect obviously.In order to characterize the surface morphology of the cleaning substrates, direct (AFM) and indirect (X-ray diffraction and Synchrotron Radiation Scattering measurements) techniques were used. However, each of these instruments is sensitive to a specific, finite range of spatial frequencies. Therefore, in order to provide the exact information of the surface, some of these methods should be combined and power spectral density theory was used.After cleaning the substrate using different methods, the Mo/Si multilayers...