SOFT-X-RAY PROJECTION IMAGING WITH MULTILAYER REFLECTION MASKS

Patterning methods for an etched multilayer mask and an absorber overl ayer mask are investigated for use at a 13-nm wavelength. RIE in SF6 i s used to etch a Mo/Si multilayer and a W absorber overlayer with a Si O2 etch-stop layer. Fine patterns as small as 0.25 mum are clearly for med. In particular, pattern sidewalls of the absorber overlayer mask a re extremely steep. The reflectivity measurement using large reflectiv e-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-mum line- and-space patterns can be printed using either mask.