Impact of Metallization Films on Scattered-Light Alignment for X-Ray Lithography

概要

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The degradation of overlay accuracy due to metallization (i.e, aluminum copper physical vapor deposition (PVD) process) on electronics devices is reported. In a video-based scattered-light alignment (SLA) system for X-ray lithography, the metal layer on the alignment mark structure affects the alignment signal quality. In this paper, we specifically focus on the significant effects of aluminum (AL) metallization on the performance of the scattered-light alignment (SLA) system. The SLA system demonstrated an overlay accuracy of 10.1 nm or less smaller (mean + 3σ) for Al films of 0.1, 0.2, 0.3 and 0.4 μm thickness. Only the 1-μm-thick Al-sputtered wafer showed a significantly poor performance of 44.4nm error (mean + 3σ). The SLA system employs two different types of alignment marks: one type uses narrow edges, while the other types uses wide edges. We estimated the mark-related alignment error using the two different types of alignment marks. The results showed that the narrow edges of the alignment marks had the advantage of smaller mean shift error compared to the wide edges of the alignment marks. Furthermore, we discuss an asymmetry-induced error in thick Al metallization.
社団法人応用物理学会の論文
1998-12-30