Soft X-ray projection imaging with multilayer reflection masks

Patterning methods for an etched multilayer mask and an absorber overlayer mask are investigated for use at a 13-nm wavelength. RIE in SF"6 is used to etch a Mo/Si multilayer and a W absorber overlayer with a SiO"2 etch-stop layer. Fine patterns as small as 0.25 @mm are clearly formed. In particular, pattern sidewalls of the absorber overlayer mask are extremely steep. The reflectivity measurement using large reflective-area samples indicates that neither method causes significant damage to the multilayer. The mask patterns are imaged onto a resist-coated wafer using a 20:1 Schwarzschild optic, confirming that 0.07-@mm line-and-space patterns can be printed using either mask.