Issues Associated with the Design and Construction of an Imaging System for Soft X-ray Lithography

Soft x ray projection lithography allows the printing of feature sizes of 1μm and smaller with reasonable depth of focus because the very short wavelength allows a small numerical aperture. Because attainable mirror reflectivities are low in this wavelength region, the number of mirrors has to be kept to a minimum. Here again the low numerical aperture helps. Compared to present deep UV (248nm.) systems, there are a number of clearcut differences that impact the design and the construction of such a system.