E-BEAM WRITTEN OPTICALLY TRANSPARENT X-RAY MASKS - 4 LEVELS FOR AN INDUSTRIAL VLSI CHIP WITH MEGABIT DESIGN RULES

For the acceptance of X-ray lithography in an industrial environment not only the high resolution and accuracy capabilities have to be demonstrated, but also the compatibility of the X-ray related processes with up to date requirements on complexity and integration of VLSI devices. To achieve this we improved our running mask technology by developing a manufacturing process for e-beam written X-ray masks for direct use in an optically aligning X-ray stepper. This mask concept was applied in a joint project with an industrial partner in which the four final lithographic steps in a VLSI CMOS fabrication were performed by means of X-ray lithography.