NZO reduction via small pitch imaging-based overlay targets

Abstract

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. ondevice 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.