The second level exposure of Alternating Phase Shift Mask has to be accomplished by e-beam lithography. However, e-beam writing on structured open chrome layers may induce severe charging and yields to deteriorate overlay accuracy. In case of charging problems, applying of conductive top coats on resists help to reduce the distortion of the second layer.
ESPACER makes the conductive layer on the e-beam resist and prevent a positioning error during e-beam writing by its shield effect. However, ESPACER required removal of its topcoat before post-exposure bake (PEB) because of the undesirable effect to the resist, due to the acid diffusion from the ESPACER film to high sensitive Chemical Amplified Resists (CARs).
Our investigations were focused on the combination of the representative positive tone CAR: FUJIFILM ELECTRONIC MATERIALS CO., LTD and the new-type ESPACER called ESPACER 300F. ESPACER 300F was possible to use the PEB process before its removal, improved by exchanging a lower mobility surfactant than before. This material also had a good wettability, a low resist-thickness losses and kept good pattern shapes of the resist. Additionally, ESPACER 300F have little influence in both overlay accuracy at the variety of pattern density and sensitivity of the resist, therefore it would be the good material for making reticles for 65nm node and beyond.