Transformation of highly (111)-oriented nanotwinned Cu films to (200)- or (211)-oriented films at 400oC annealing using Ta and Co adhesion layers

• Main Authors: Cho, Meng-Yi, 卓孟毅
• Other Authors: Chen, Chih
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/4nfqc6

碩士 === 國立交通大學 === 工學院半導體材料與製程設備學程 === 107 === In back-end-of-line (BEOL) metallization, TaN/ Ta has been widely used for Cu interconnect barrier layer to prevent Cu atoms from penetrating into porous low-k materials. As the continuous scaling in microelectronic devices to 28nm and beyond, Cu interconnects in BEOL face reliability challenges, especially in electromigration (EM). A thin adhesion enhancement Co layer between TaN/ Ta and Cu become a popular material to improve BEOL Cu interconnect systems reliability. Electroplated (111)-oriented nanotwinned Cu (nt-Cu) as a novel interconnect and packaging industry has attracted a lot of attention in recent years because it has a higher strength than regular Cu, but possesses the same resistivity as bulk Cu. Another excellent property of nt-Cu is extremely anisotropic single crystal growth, which has potential for reducing grain boundary scattering problem in BEOL Cu interconnect for 28nm and beyond. Therefore, the grain growth of direct-current electroplated (111)-oriented nt-Cu on 10nm Ta and Co adhesion layer at 400oC annealing are studied. The microstructure of the nt-Cu films are analyzed using X-ray diffraction, focused ion beam and electron backscatter diffraction. In this paper, Ta/nt-Cu and Co/nt-Cu systems are compared for their crystallinity of seed layers, electroplated layers, and additional metal capping layers before and after 400oC annealing for 1 hour. The results indicated that after annealing, nt-Cu with strong (111)-oriented Cu seed layer on the Ta adhesion layer would transform to (200)/(211)-oriented Cu films, and with big grain size of Cu seed which contains (200)-oriented grains on Co adhesion layer would transform to highly (200)-oriented large crystals. However, Ta/nt-Cu film can also grow to highly (200)-oriented large crystals by increasing deposited temperature of Cu seed layer from -14oC to 60oC.