Effect of Chemical Composition on Adhesion of Directly Electrodeposited Copper Film on TiN

Choe

et al. 2015

J. Electrochem. Soc.

The electrolyte for Cu superfilling generally consists of copper sulfate, sulfuric acid, a chloride ion, an accelerator, and a suppressor. In this study, the characteristics of citric acid-based electrolytes and the interaction between citrate species and accelerators are investigated, with the ultimate goal being the replacement of both sulfuric acid and the suppressor with citric acid. Electrochemical impedance measurements were adopted to measure the changes in solution and charge transfer resistances with respect to citric acid and accelerator concentrations. In addition to a decrease in solution resistance resulting from the addition of citric acid, charge transfer inhibition was observed during Cu electrodeposition, which is likely the result of adsorption of citrate species onto Cu surface. A competitive adsorption between the citrate species and the accelerator was also observed and the new additive system was applied to the feature filling in the absence of the conventional polyethylene glycol suppressor. Using this new copper sulfate, citric acid, chloride ion, and accelerator system, trenches were successfully bottom-up filled, resulting in no internal defects.

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Electrochemical Behavior of Citric Acid and Its Influence on Cu Electrodeposition for Damascene Metallization

Choe

et al. 2015

J. Electrochem. Soc.

“…Kim et al reported that in the pH = 5.8 − 6.5 interval, depending on Cu concentration, (Cu 2 Cit 2 (OH) 2 ) 4− is reported to be the most stable complex species in solution and it suppresses the direct reduction of Cu from the electrolyte [28].…”

Section: Resultsmentioning

confidence: 99%

A Cyclic Voltammetry Study on Electrodeposition of Cu-Zn Alloy Films: Effect of Ultrasonication Time

Yurdal

Karahan

2017

Acta Phys. Pol. A

Copper zinc alloys were electrodeposited in the form of thin films. Electrodeposition process was carried out in non-cyanide aqueous medium, under constant current. Effect of pre-deposition ultrasonication of solution was investigated. In other words ultrasonic treatment was applied only before the electrodeposition. Solutions were subjected to high-energy ultrasonication for increasing times. Cyclic voltammetry was used to understand changes occurring due to duration of ultrasonication. No ultrasonication was applied during deposition. Atomic composition of resultant films were revealed by MP-AES. It was found that implementation of ultrasonic treatment before electrodeposition affects CV characteristics, when compared to non-ultrasonicated solution. Atomic composition of fabricated samples were found to be close to each other, some of them showing more deviation.

“…In a previous study, Cu 2 (Cit) 2 OH 3− was useful to electrodeposit a very thin, uniform Cu film, and CuCit − was effective in promoting interfacial adhesion between Cu electrodeposits and TiN diffusion barrier layer. 34 Thus, it is expected that the dominant formation of CuCit − and Cu 2 (Cit) 2 OH 3− may also be helpful in electrodepositing Cu thin films directly on Ti diffusion barrier layer. Figure 2 shows a CV curve plotted in the cathodic potential region up to −2.0 V in the Cu-Cit electrolyte of pH 3.40.…”

Section: Resultsmentioning

confidence: 99%

Surface Morphology Evolution of Cu Thin Films Electrodeposited Directly on Ti Diffusion Barrier in Citric Acid

2015

J. Electrochem. Soc.

Self Cite

The formation of Cu thin film directly on Ti diffusion barrier by electrodeposition is important for next generation Cu interconnect in Si-based microelectronic devices. It depends on the surface morphology evolution of Cu deposit at the initial stage of nucleation and growth. In this study, we investigated the surface morphology evolution of Cu thin film on Ti in citric acid solution, introducing several simple ways to determine the stages of nucleation, Cu nuclei overlap, and Cu film formation with deposition time. During potentiostatic Cu deposition, studies on morphology change using the chronoamperometry, the change of surface roughness, and the change of sheet resistance and sheet resistivity are carried out along with microscopic observation. Resultant surface morphology of Cu deposit on Ti is greatly influenced by nucleation behavior, and its dependence on deposition potential is also studied in relation with the calculation of critical Cu nucleus size. According to the suggested ways, it is available to indirectly observe the transition of Cu nuclei to Cu thin film on Ti diffusion barrier during electrodeposition. Electrodeposition has been widely used to fabricate Cu interconnect in ultra large scale integrated Si microelectronic device since 1997.1 As the width of Cu interconnect line in the Si device gets shrinking under 45 nm, more sophisticated control of Cu electrodeposition process parameters is required to fill dual-damascene structures with void-free Cu. Many researchers have tried to understand the behaviors of additives like suppresser, leveler, and accelerator in electrolytes, which are valid for Cu growth control within sub-45 nm wide dual-damascene structures of the Si device.2-5 Another effort has been made to give more space for Cu fill within dual-damascene structures by eliminating a seed layer for Cu electrodeposition. It has been reported that seedless Cu electrodeposition directly on diffusion barrier is a promising approach to fabricate sub-45 nm Cu interconnect line.6-12 Cu was electrodeposited directly on non-metallic diffusion barriers such as W 2 N, TiN, and TaN. However, seedless Cu electrodeposition is moderately limited for wafer-level Cu interconnect fabrication. Significant difference of deposition current density across a Si wafer leads to the non-uniformity of thickness and microstructure of an electrodeposited Cu layer because non-metallic diffusion barrier layers have much higher electrical resistivities than a Cu seed layer.Metallic diffusion barriers, which are mostly transition metals such as Ru, W, Ta, Ti, Cr, Ni, Co, Pt, Pd, Nb, Mo, Ir, and Os, have been suggested due to their relatively high electrical conductivity, excellent resistance to Cu diffusion, and immiscible characteristic with Cu. 13-18Ru among them has been most frequently treated for next generation diffusion barrier of Cu interconnect so far. [19][20][21] We have previously reported seedless Cu electrodeposition on W and Ta diffusion barriers with regard to the nucleation and growth of Cu thin film....