Mixed-proximity holographic mask technology for 50-nm VLSI by x-ray lithography

The development of mixed proximity and binary phase holographic x-ray masks for feature sizes of 50nm is continued for mask to wafer gaps of 50micrometers for printing into photoresist with 1nm x-rays. The maximum gap for binary holographic correction for image blurring on reconstruction is shown to be limited by the symmetry impressed by the binary phase encoding. The computation of the holograms is described. A hologram is calculated in patches limited in size by computational restrictions and procedures are described for superposition at the wafer of structures reconstructed from adjacent patches. The fabrication of binary masks is well suited to electron beam writing.