长等待时间下铜互连线形成球状缺陷的机理研究及解决方案

Formation Mechanism and Solution for Hillock in Cu Interconnection Due to Long Q-Time

随着集成电路向高密度小尺寸方向发展,铜互连已成为目前集成电路主要使用的互连技术,但球状缺陷的形成会影响产品的质量.本文研究了长等待时间下铜互连线中球状缺陷的形成机理,分析了其造成器件失效的原因,并提出了相应的解决方案.研究显示,前道工序应力残留致铜晶界处应变再结晶是这种形式球状缺陷形成的主要原因.球状缺陷会使两层金属之间形成额外通孔,从而引起短路或漏电,导致器件失效.最后提出了相应的解决方案,通过正交实验发现铜电镀退火温度降低50℃,氮化硅淀积速率降低1 nm/s,氮化硅的膜厚提高10 nm能够有效改善这一现象.

With integrated circuit （IC） becoming higher in density and smaller in size, Cu interconnec tion has developed into a dominant interconnection technology. However, the formation of hillock would affect the product quality. The formation mechanism of hillock due to long queue time （Qtime） was ana lyzed in this paper to explore the device failure mode and a corresponding solution was put forward . The results show that the main hillockformation factor is the stress residual on grain boundaries of copper at oms from previous procedure. Hillock brought about excessive via bridge between metal layers 4 and 5, which would induce current leakage or short circuit, thus leading to device failure. The orthogonal test showed that the yield of product was improved significantly when electro chemical plating （ECP） annea ling temperature decreased by 50 ℃, silicon nitride （SiN） deposition rate decreased by 1 nm/s and SiN film thickness increased by 10 nm.