A Effect of Halide on Cobalt Electrodeposition for through-Silicon-Via(TSV) Application
Authors: Kim Youjung , Lee Jinhyun , Park Kimoon , Lee Chaerin , Yoo Bongyoung 
Published: February 2020

The size of integrated circuit (IC) devices had gradually decreased. Because of limit to reduction, 3D interconnection technology had emerged. As one of the 3D interconnection technologies, Through Silicon Via (TSV) replaced conventional wire bond by making vertical electrical connections. TSVs could increase the device performance because TSV had advantages such as higher interconnection density, shorter length of interconnection, lower power consumption, and lower electrical resistance [1].

TSV was mainly plated with copper with low resistance and low electro-migration. However, copper annealing process, metal interconnect process and bonding process between chips and chips or wafers and wafers were performed at high temperature in BEOL, which causes problems such as thermal extrusion and keep-out zone. Thermal extrusion is enough to make the defect and crack at insulating layer or metal interconnect on TSV. And the keep-out zone could cause some degradation in device performance [3]. Therefore, Cobalt was used to fill TSV as alternative material which can reduce this problem because the CTE of cobalt was lower than that of copper. However, while many studies on copper TSV filling was reported, studies on cobalt TSV filling was insufficient.

For the TSV bottom-up filling, TSVs were conventionally filled with some additives such as accelerator and suppressor by using the electrochemical deposition. In addition, halide was used to enhance adsorption of suppressor. Many studies confirmed effect of halide in copper electrodeposition [2, 4].

In this study, high-aspect ratio TSVs was filled with cobalt with suppressor as the single additive using the electrochemical deposition. The filling behavior was affected by suppressor concentration and the effect was saturated. In copper electrodeposition, halide ion is added because adsorption of suppressor is affected by chloride [2, 4]. Therefore, chloride, one of the halide, was added to confirm the effect of halide on cobalt electrodeposition. In cobalt electrodeposition, the role of chloride was different from that of copper electrodeposition. Electrochemical analysis explains the effect of chloride concentration in the cobalt filling.

REFERENCES

[1] Sanghyun Jin, Geon Wang, and Bongyoung Yoo, “ Through-Silicon-Via (TSV) Filling by Electrodeposition of Cu with Pulse Current at Ultra-Short Duty Cycle”, Journal of The Electrochemical Society, 2013, 160 (12) D3300-D3305

[2] Liu Yang, Aleksandar Radisic, Johan Deconinck, and Philippe M. Vereecken, “ Modeling the Bottom-Up Filling of Through-Silicon vias Through Suppressor Adsorption/Desorption Mechanism”, Journal of The Electrochemical Society, 2013, 160 (12) D3051-D3056

[3] Suk-Kyu Ryu, Kuan-Hsun Lu, Tengfei Jiang, Jang-Hi Im, Senior Member, Rui Huang, and Paul S. Ho, Fellow,“ Effect of Thermal Stresses on Carrier Mobility and Keep-Out Zone Around Through-Silicon Vias for 3-D Integration”, IEEE TRANSACTIONS ON DEVICE AND MATERIALS RELIABILITY, 2012, 6, VOL. 12, NO. 2, 255-262

[4] Ning Xiao, Deyu Li, Guofeng Cui, Ning Lia, Qing Li, Gang Wu, “Adsorption behavior of triblock copolymer suppressors during the copper electrodeposition”, Electrochimica Acta, 116 (2014) 284– 291