Superlattices for EUV and X-Ray Mirrors
Mirrors in the extended ultraviolet (EUV)
and x-ray regions are superlattices that reflect by Bragg
diffraction. An illustration of a superlattice x-ray mirror
is shown in the accompanying figure. High
reflectivities of ~70% in the EUV at ~12 nm can be obtained
using Mo/Si superlattices. These EUV mirrors are important
for next generation EUV lithography. Current Mo/Si superlattices
fabricated using ion beam spattering suffer from high defect
densities. Lower defect density superlattices will be necessary
for EUV lithography.
Superlattices can be fabricated using ALD
techniques. These superlattices may produce well-defined multilayers
that challenge the ion beam spattering fabrication methods.
We are currently setting up to deposit Mo/Si superlattices
using ALD. After demonstrating the fabrication of these Mo/Si
superlattices, the structural properties will be evaluated
prior to EUV reflectivity measurements.
