Current Status Of Mo-Si Multilayer Formation In Aset For Low-Defect-Density Mask Blanks For Euv Lithography

To find the most suitable setup of the Mo and Si targets and substrate for the formation of Mo-Si multilayers with a low defect density, three deposition configurations (upward, horizontal, and off-axis) for magnetron sputtering (MS) were studied. It was found that the horizontal configuration yielded the lowest defect count and was also the best for ion beam sputtering (IBS). A defect density as low as 1 defect/cm(2) has been achieved for Mo-Si multilayers grown by IBS or MS. A new approach to reducing the thickness of the interface layer between Mo and Si layers that involves the use of an assisted ion beam (AIB) was found to be effective. Transmission electron microscopy revealed that, during MS, AIB treatment of a Si surface before deposition of a Mo layer reduced the thickness of the interface layer to zero. Angle-dependent X-ray diffraction measurements of multilayers showed sharp reflection peaks, indicating considerable improvement in the interface structure.