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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 new ternary amorphous compound thin film was used as a barrier layer for Cu interconnection. The heterojunction of Cu (120 nm) / Ni-Al-N (10 nm) / Si was fabricated by RF magnetron sputtering. The transport properties, microstructure and surface morphology of high vacuum annealed samples at different temperatures were investigated by four-probe tester, X-ray diffraction and atomic force microscopy. The results show that the amorphous Ni-Al-N film can remain amorphous after high temperature treatment at 650 ℃ without obvious reaction and mutual diffusion between the films, indicating that amorphous Ni-Al-N has a good barrier effect , Can be used as a barrier material for Cu interconnects. In addition, compared with the Ni-Al diffusion barrier material, the incorporation of N fills the defects of the barrier layer, reduces the roughness of the Cu film and makes the surface of the film more smooth and compact, thereby playing the role of grain refinement. The research on the failure mechanism of the Ni-Al-N barrier shows that the failure mechanism of the Ni-Al-N barrier is different from the conventional Cu-Si interdiffusion mechanism. The stress in the Cu film causes the particles to coalesce to form large clusters, Peeling from the barrier can lead to Cu / Ni-Al-N / Si structure failure.