In this work, we combined the computational simulation and experiments to explore the convection on filling characteristics of the micro through-holes (THs) with multiple aspect ratio (ARs). The micro THs with ARs 6.25:1∼1.67:1 (thickness 500 μm) were chosen as research targets. The computational model was established based on the actual state of Haring-Cell, and attention was fixed on the convection distribution in the micro THs. The interaction mechanism of additives with the changing ARs systematically explored by electrochemical measurements. The simulation results show that the convection in the micro THs center declines with the increasing AR. The convection-dependent additives formed diverse adsorption states around the micro THs with different ARs, providing two kinds of Cu filling processes, including defect-free filling and insufficient filling. The weak convection is conducive to the adsorption of the accelerator and detrimental to the adsorption of the suppressor, which accelerates the Cu electrodeposition and elevates the throwing power (TP) value to over 100% to form the defect-free filling. Strong convection is instrumental in the adsorption of the leveler so that a uniform Cu film thickness can be obtained but to create the insufficient filling. Simulation and electroplating experiments show that the AR of 3.33:1 is the cut-off point of the flow field distribution and the electroplating processes. The micro THs with AR higher than 3.33:1 can be fully filled with a uniform bright Cu surface.
Fuliang Wang,Yuhang Tian,Kang Zhou,Rui Yang,Tian Tan,Yan Wang,Wenhao Yao
Through silicon via (TSV) is a promising interconnect technology in three-dimensional (3D) integration which has large packing density, improves efficiency and consumes less energy. Since the optimization process of multi-additives system is complicated to achieve void-free TSV copper filling, the use of a single additive become a new trend. In this paper, the using of a triblock copolymer ethylene oxide (EO) - propylene oxide (PO) - ethylene oxide (EO) as a single additive in TSV copper electrodeposition was investigated. High and low concentration of EPE (0.02 g/L and 0.002 g/L) were used for the filling experiment at different current densities. It was found that low concentration EPE had stronger inhibition ability, and achieved “V shape” filling at 0.3 ASD (A/dm 2 ). However, EPE of high concentration would form micelles in electrolyte, resulting in the decrease of inhibition ability. We proposed a mechanism for the different EPE concentrations to explan the phenomenon. In addition, the effect of ultrasonic agitation on EPE filling performance was investigated. With the ultrasonic agitation , bottom-up filling can be achieved at 0.02 g/L, and filling rates can be increased at 0.002 g/L. This can be attributed to the cavitation of the ultrasound which can promote the mass transfer and clean the activated electrode.
The void-free deposition of small-sized and high-aspect ratio interconnect structures requires stronger suppressors than conventional polyethers. In this work, thioether was introduced into polyether to develop novel suppressors with improved adsorption on electrode. The structure of thioether-modified polyether can be easily tailored by choosing proper polyether and thiol compound, thus providing a simple way to regulate electrochemical properties of the suppressor. The electrochemical and copper filling performance related to the molecular structure of novel suppressors were systematically investigated. Thioether-modified polyether, which retains the strong polarizability of typical suppressor and exhibits high resistance to accelerator desorption, can significantly suppress copper deposition on feature sidewalls. This enabled defect-free filling of narrower features at a concentration much lower than the typical usage concentration of suppressor. The modified polyethers with ethylene-propylene-ethylene (EPE) oxide triblock ether chains exhibited higher polarization strength and concentration dependence, facilitating the higher deposition current at the bottom during filling. The length and block ratio of ether chain further influenced the anti-desorption ability of the modified polyether, thereby impacting their suppression on sidewalls, which is crucial in filling process. The convenient structural adjustments for thioether-modified polyether, combined with the derived structure-property relationship, contribute to the development of new suppressors with strong adsorption performance.
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