Analysis of Printability of Scratch Defect on Reflective Mask in Extreme Ultraviolet Lithography

概要

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The aim of this study was to investigate the printability of a scratch defect on the surface of a glass substrate. Simulations revealed that smoothing deposition made a scratch more printable than non-smoothing deposition did. Smoothing deposition changes the topography of a scratch by making it shallower and wider as it propagates from the bottom to the top of a Mo/Si multilayer on a reflective mask blank. This change in topography shifts the phase, thereby reducing the energy of light reflected from the mask. In contrast, non-smoothing deposition preserves the topography of a scratch from the bottom to the top of a multilayer. As a result, non-smoothing deposition changes the phase less than smoothing deposition does, which makes a scratch less printable. An analysis of the intensity of diffracted rays clarified how much of the energy used to create a printed image was lost at the pupil due to a defect: The energy loss was approximately 10 times larger for smoothing than for non-smoothing deposition; and thus, the change in the critical dimension of a printed image on wafer was also much larger for smoothing deposition.
2006-12-15