NZO reduction via small pitch imaging-based overlay targets

Abstract

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On-product overlay (OPO) control in the DRAM process has become a critical component from node to node to produce high device yield. To meet OPO node goals, Non-Zero Offset (NZO) and its stability across lots must be monitored and controlled. NZO is the bias between overlay (OVL) on-target measurement at After Development Inspection (ADI) vs. on-device measurement at After Etching Inspection (AEI). In this paper, we will present Imaging-Based Overlay (IBO) metrology data at ADI of two different marks, segmented AIM® with design rule patterns and robust AIM (rAIM®) with Moiré effect with a small pitch. NZO analysis will be presented for each target type including basic performance.