Fabrication and characterization of Cu-Sn-Ni-Cu interconnection microstructure for electromigration studies in 3D integration
Fabrication and characterization of Cu-Sn-Ni-Cu interconnection microstructure for electromigration studies in 3D integration
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DOI：
10.1108/ssmt-10-2015-0031
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发表时间：
2016-04
影响因子：
2
通讯作者：
Ming Xiao;Walid-Madhat Munief;Fengshun Wu;R. Lilischkis;Tobias Oberbillig;M. Saumer;W. Xia
中科院分区：
文献类型：
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作者：
Ming Xiao;Walid-Madhat Munief;Fengshun Wu;R. Lilischkis;Tobias Oberbillig;M. Saumer;W. Xia
目的制备一种新型Cu-Sn-Ni-Cu互连微结构，用于三维集成电迁移研究。设计/方法/方法采用不同电镀工艺的三掩模光刻工艺制备Cu-Sn-Ni-Cu互连微结构。该微结构由衬垫和导电线为底层，直径为10 ~ 40 μm的Cu- sn - ni -Cu柱为中间层，Cu导电线为顶层组成。底层采用升降工艺。采用顺序电镀工艺，采用光刻法制备了Cu-Sn-Ni-Cu柱。为了制备顶层，引入了一层溅射铜层，以防止中间层光刻胶的形成。通过最后的Cu电镀工艺，成功地实现了Cu- sn - ni -Cu互连微观结构。发现铜锡柱的表面形貌是由有序排列的四方锡晶粒密集排列而成的团簇。在Cu/Sn界面处观察到Cu原子向Sn相的扩散。Cu-Sn-Ni-Cu柱表面平整，平均粗糙度为13.9 nm。此外，在Cu-Sn-Ni-Cu柱的Sn层和顶部Cu层之间引入Ni层可以减缓Cu原子向Sn相的扩散。该过程通过使用四点探头测量检查电气性能来验证。本文将三掩模光刻工艺与Cu、Sn、Ni、Cu连续电镀工艺相结合，为今后的电迁移研究提供了一种制备互连微结构的新方法。
Purpose The purpose of this paper is to fabricate a new Cu-Sn-Ni-Cu interconnection microstructure for electromigration studies in 3D integration. Design/methodology/approach The Cu-Sn-Ni-Cu interconnection microstructure is fabricated by a three-mask photolithography process with different electroplating processes. This microstructure consists of pads and conductive lines as the bottom layer, Cu-Sn-Ni-Cu pillars with the diameter of 10-40 μm as the middle layer and Cu conductive lines as the top layer. A lift-off process is adopted for the bottom layer. The Cu-Sn-Ni-Cu pillars are fabricated by photolithography with sequential electroplating processes. To fabricate the top layer, a sputtered Cu layer is introduced to prevent the middle-layer photoresist from being developed. With the final Cu electroplating processes, the Cu-Sn-Ni-Cu interconnection microstructure is successfully achieved. Findings The surface morphology of Cu-Sn pillars consists of densely packed clusters which are formed by an ordered arrangement of tetragonal Sn grains. The diffusion of Cu atoms into the Sn phases is observed at the Cu/Sn interface. Furthermore, the obtained Cu-Sn-Ni-Cu pillars have a flat surface with an average roughness of 13.9 nm. In addition, the introduction of Ni layer between the Sn and the top Cu layers in the Cu-Sn-Ni-Cu pillars can mitigate the diffusion of Cu atoms into Sn phases. The process is verified by checking the electrical performance using four-point probe measurements. Originality/value The method described in this paper which combined a three-mask photolithography process with sequential Cu, Sn, Ni and Cu electroplating processes provides a new way to fabricate the interconnection microstructure for future electromigration studies.