DEFECT COVERAGE PROFILE AND PROPAGATION OF ROUGHNESS OF SPUTTER-DEPOSITED MO SI MULTILAYER COATING FOR EXTREME-ULTRAVIOLET PROJECTION LITHOGRAPHY/

The presence of defects in multilayer reflective coatings to be used a s mask blanks for extreme ultraviolet projection lithography can cause significant reduction in image intensity. The extent of the reduction depends on the size and position of the defects and also on the manne r in which the deposition process covers the underlying defect. If the deposited film causes lateral propagation of defect geometry and does not reduce the step height, even a hundred angstrom-sized defect migh t cause an observable effect. However, if the deposition process can r educe the defects' height and does not increase their effective size, the effect of defects on image would be less severe. Atomic force micr oscopy and transmission electron microscopy was used to study multilay er coating deposition profiles over programmed defects. It was found t hat the step height and edge slope is significantly reduced after film deposition with small lateral propagation of defect geometry. Roughne ss of the evaporated programmed defects was significantly reduced by t he multilayer deposition process. A 200 nm Si buffer layer deposited b efore multilayer mirror deposition further smooth out the small featur es. However it also increases the roughness over the initially smooth wafer, resulting in lower achievable multilayer coating reflectivity.