铜互连扩散阻挡层工艺优化

针对金属线间击穿电压小、可靠性差的问题，对铜扩散阻挡层（包括钽阻挡层厚度和氮化硅阻挡层薄膜质量）进行研究优化。使用自对准双重图形（SADP）方法能够使金属互连线的特征尺寸缩小，使得互连线扩散阻挡层的厚度期望降低。通过制备不同厚度的钽阻挡层对金属互连体系电阻和击穿电压做详细对比分析，发现硬质的钽金属对化学机械研磨（CMP）产生影响，导致互连体系电阻和击穿电压随着钽阻挡层厚度减小而增加，过薄的阻挡层会导致阻挡性能降低、整体晶圆均一性变差；铜线界面上存在的氧元素极大地降低了氮化硅的黏附性，影响阻挡层性能。在氨气预处理阶段通入不同流量的氨气，在预沉积阶段改变预沉积时间，增加过渡阶段，通过实验分析氮化硅的黏附性，结果证明:氨气流量的增加、预沉积时间的减少、过渡阶段的增加能提高氮化硅的黏附性，改善了薄膜阻挡能力。 

Optimization of diffusion barrier process on copper interconnection

Facing the problems about low breakdown voltage and poor reliability of the metal interconnection, the copper diffusion barrier including the thickness of the tantalum barrier and the quality of silicon nitride barrier film was studied and optimized. The Self-Aligned Double Pattern (SADP) method can reduce the critical dimension of metal interconnection and cut down the thickness expectation of the interconnection wire diffusion barrier. In this paper, the resistance and breakdown voltage of metal interconnetion system are compared and analyzed in detail by preparation of tantalum barriers with different thickness. It is found that the hard tantalum material has an impact on Chemical Mechanical Polish (CMP). As the thickness of tantalum decreases, the resistance and breakdown voltage of the interconnection system will increase, and the over-thin barrier will degrade the performance of the barrier and make the uniformity of the whole wafer worse. Meanwhile, the presence of oxygen at the copper wire interface can greatly reduce the adhesion of silicon nitride, which degrades the performance of the silicon nitride barrier. In this experiment, the adhesion of silicon nitride is analyzed by feeding different flow rates of ammonia during the ammonia treatment stage, changing the pre-deposition time and increasing the transition stage in the pre-deposition stage. Experiments show that the adhesion of silicon nitride can be improved with the increase of ammonia flow rate, the decrease of pre-deposition time and the addition of the transition stage, and the blocking ability of film is improved.