Alternating aperture phase shift mask process using e-beam lithography for the second level

The combination of conductive topcoat ESPACER Z300 and positive tone CAR FEP171 was investigated in detail for the second level patterning of Alternating Aperture Phase Shift Masks (AAPSM) using e-beam lithography. Chrome load variations between 2 and 50% with the corresponding deviation of the second level pattern, homogeneously and unevenly distributed on the mask, had no significant impact on placement and overlay accuracy. No clear defect increasing could be measured when applying ESPACER top coat. The quartz etch selectivity of FEP171 was identically with the widely accepted laser resist IP3600 and a good etch depth linearity was achieved down to 200nm feature size. Finally, the performance of the developed process has been demonstrated on a 65nm node device design.