Electroplated Cu is being used by the major semiconductor .manufacturers as an interconnect material, because it offers a lower line resistance and better electromigration performance over conventional A1 metallization. This paper describes the mechanism of "super-fill" as well as gap fill, microstructure, and film composition of electroplated copper. A combination of optimized Cu plating additive chemistry and current waveform enable complete gap fill of 0.07 -0.1 pm features (AR > 10: 1) as well as strong (1 1 1) texture, large grains (> 3 pm) with a large fraction of twin grain boundaries and controlled impurities content in electroplated Cu films. Electroplating process stability was maintained through the on-line analysis (p/t <0.3) of organic and inorganic bath ingredients and their replenishment. IntroductionIt has been reported in the literature (1, 2) that copper electroplating (EP) has the ability to provide bottom up fill or "super-fill" resulting in the complete gap fill of narrow trenches and vias. This is commonly assigned to the action of organic additives added in small amounts to the plating bath. However, the mechanism of action of these additives is still unclear. The role of the additives, current conditions, and substrate texture on the microstructure and impurities incorporation into plated Cu film is also not well understood. We will review in this paper the mode of action of plating additives and provide simulation and experimental results of gap fill in sub 0.1 pm features. The simulations were on wafer and reactor levels such as tertiary current distribution on the wafer surface and fluid flow in the plating reactor as well as feature level including shape evolution. Cu electrodeposited structure as a function of current density, inhibition strength and substrate texture will be discussed. Impurities were also studied in the plated copper vs. plating conditions.
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