Printing characteristics of proximity x-ray lithography and comparison with optical lithography at 100 and 70 nm technology nodes

Abstract

The printing characteristics of proximity x-ray lithography (PXL) were compared with those of ArF and F2 optical lithography using model patterns of memory and logic devices at 100 and 70 nm technology nodes. Aerial-image simulations of both optical lithography and PXL were carried out, and exposure experiments were performed to confirm the simulation results for PXL. Both the aerial images and the exposure results show that PXL has sufficient resolution for patterns with a 100 nm minimum feature size without the need for any additional resolution enhancement techniques (RETs). It exhibits better pattern printing fidelity than either ArF or F2 lithography with strong RETs, such as an alternate-type phase shift mask and off-axis illumination techniques. PXL provides a wide latitude (on the order of microns) in the proximity gap, and is robust with regard to critical dimension errors in mask patterns. For the optical lithography, the fidelity for complex patterns and the narrow depth of focus (DOF) are still issues to be resolved. At the 70 nm node, PXL provides acceptable resolution even at a gap of 10 μm, while F2 lithography requires further advanced RETs to achieve sufficient resolution and an acceptable DOF.

Fabrication of x-ray masks using evaporated electron sensitive layers for back patterning of membranes

“…1 Recently, other researchers 2,3 have achieved 50 nm resolution with PXL by using a 10 and 15 m gap between the mask and the wafer. Another study 4 shows that PXL can print 35 nm features using a higher energy radiation and smaller proximity gap ͑р5 m͒.…”