Photo cell monitoring inspection methodology employing a complementary strategy of advanced darkfield and high sensitivity brightfield inspection tools

Lithography process monitoring has always been a challenging step in foundry fabs. Broadband brightfield inspectors are used to meet the sensitivity requirement on low contrast photo-cell monitoring (PCM) process layers. However, the throughput of brightfield inspectors often requires reducing sampling rates and/or reducing wafer inspection coverage. In this paper, we introduce an innovative and highly efficient inspection methodology for 2x/4xnm PCM applications. This new defect inspection scheme utilizes a complementary inspection tool set comprised of an advanced darkfield inspection tool and a high sensitivity brightfield inspection tool. This combination provides effective process monitoring of PCM layers and significantly reduces Cost of Operation (CoO).