非晶Ni-Al-N薄膜用作Cu互连阻挡层的研究

Growth of Ni-Al-N Diffusion Barrier Films in Cu Metallization

以一种新的三元非晶化合物薄膜作为Cu互连的阻挡层,采用射频磁控溅射法构架了Cu(120 nm)/Ni-Al-N(10nm)/Si的异质结。利用四探针测试仪、X射线衍射仪和原子力显微镜研究了不同温度下高真空退火样品的输运性质、微观结构与表面形貌。实验发现非晶Ni-Al-N薄膜经过650℃的高温处理仍能保持非晶态,各膜层之间没有明显的反应和互扩散存在,表明非晶Ni-Al-N具有良好的阻挡效果,可以用作Cu互连的阻挡层材料。另外,相对于Ni-Al扩散阻挡层材料,N的掺入填充了阻挡层的缺陷,降低了Cu膜粗糙度,使薄膜表面更加平整致密,起到了细化晶粒的作用。对Ni-Al-N阻挡层的失效机制的研究表明Ni-Al-N阻挡层的失效机制有别于传统的Cu-Si互扩散机制,Cu膜内应力导致其颗粒内聚形成大团簇,与阻挡层剥离会导致Cu/Ni-Al-N/Si结构失效。

A novel type of amorphous ternary films was developed by RF magnetron sputtering to effectively block the diffusion in Cu metallization of Si device fabrication.The impact of annealing temperature on the film quality was studied.The microstructures and transport behavior of the Cu（120 nm）/Ni-Al-N（10 nm）/Si hetero-junction were characterized with X-ray diffraction,atomic force microscopy and conventional probes.The results show that the compact,smooth,amorphous Ni-Al-N films,annealed at 650℃,worked very well as a diffusion barrier,and that the annealing temperature strongly affects its microstructures.Possible mechanisms were also tentatively discussed.