Articles you may be interested inQuantitative analysis of electron energy loss spectra and modelling of optical properties of multilayer systems for extreme ultraviolet radiation regime Impact of electron scattering in extreme ultraviolet reflective multilayer (ML) on electron image was investigated. The secondary electron emission coefficient of Ru capped ML was lower than that of Ru bulk layer when the incident electron energy was more than 0.5 keV. In ML, the backscattered electrons (BSEs) diffused laterally along the Si layer and escaped from the Ru surface, while generating secondary electrons. As a result, spatial intensity distribution of the emitted electrons within the ML sample was broader than that of the Ru bulk sample. The deep and broad undershot dip appeared in the profile of scanning electron microscope image for knife-edge pattern on ML sample. This was because the BSEs near the edge diffused laterally and were blocked from escaping from the sample surface by the absorber layer. In the case of hp 50 nm line-and-space (L/S) pattern, dips appeared only for Ru bulk samples, because the dense L/S pattern profile is essentially a summation of two opposing knife-edges. Simulated diffusion lengths were in good agreements with experimentally obtained dip widths. The influential range of laterally diffusion effect was from 3 to 20 keV.
Thin absorber defects called residual-type defects are etching residues that tend to become more discernible as the pattern size of the extreme ultraviolet (EUV) mask shrinks. Projection electron microscope (PEM) images of the residual-type defects with various thicknesses were investigated using Monte Carlo simulation. In the case of the secondary electron image, the thickness of the defect was identified by the defect's signal intensity. It was found that the material and its relative thickness affected the signal intensity. In the case of the mirror electron image, three kinds of defects were selectively identified by controlling the primary electron energy. When the energy distribution of the primary electrons was taken into account, these defects were identified by the defects' signal intensities. It was found that the surface potential of the residual-type defects on the EUV mask greatly affected the mirror electron image. These results suggest that the thickness of the residual-type defect is identifiable by the PEM technique, and the defect selectivity is greatly affected by the thickness of the oxide layer when mirror electrons are used.
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