Test Pattern Design for Plasma Induced Damage on Inter-Metal Dielectric in FinFET Cu BEOL Processes

High-density interconnects, enabled by advanced CMOS Cu BEOL technologies, lead to closely placed metals layers. High-aspect ratio metal lines require extensive plasma etching processes, which may cause reliability concerns on inter metal dielectric (IMD) layers. This study presents newly proposed test patterns for evaluating the effect of plasma-induced charging effect on the integrity of IMD between closely placed metal lines. Strong correlations between the plasma charging intensities and damages found in IMD layers are found and analyzed comprehensively.