Fabrication of Cu-Ag Interconnection Using Electrodeposition: The Mechanism of Superfilling and the Properties of Cu-Ag Film

Abstract

The dimensions of Cu interconnections in electronic devices have been rapidly reduced to achieve high integration. The continual down scaling considerably increases both the electrical resistivity and the probability of electromigration failure. The addition of a secondary metal into Cu can improve the resistance against electromigration. However, the co-deposition of a secondary metal inevitably reduces the electrical conductivity. Thus, the main consideration in alloying with Cu is to find a secondary metal that shows the lowest resistivity. Ag has been known as the most appropriate. In this research, the superfilling of Cu-Ag and its mechanism are investigated. The area reduction at the surface with negative curvature induces the accumulation of adsorbed accelerators, finally resulting in local increment of the deposition rate of Cu-Ag at the bottom of a trench. Additionally, the microstructure of Cu-Ag film is investigated, and it is confirmed that Cu-Ag film exhibits superior oxidation resistance and mechanical strength without severe deterioration of the electrical conductivity compared to pure Cu.Cu has been widely used to fabricate the metal interconnections in various electronic devices through the damascene process, which involves the deposition of an intermetallic dielectric, the patterning of trenches or vias through lithography, the deposition of diffusion barrier and Cu seed layers, the electrodeposition of Cu, and chemical mechanical planarization (CMP) in sequence. 1-3 As the dimensions of electronics have been continually reduced to the nanoscale range, the development of new conducting materials with improved electrical conductivity and enhanced electromigration resistance and mechanical strength are now needed to achieve high-speed and reliable electronic microprocessors. 4-8

Bottom-Up Electrodeposition of Zinc in Through Silicon Vias

“…15,16 The additive combinations of accelerator and suppressor associated with Damascene copper superfilling of submicrometer features have also been applied to much larger, lower aspect ratio microvias and more recently higher aspect ratio Through Silicon Vias (TSVs). [17][18][19][20][21][22][23][24][25] However, at these larger length scales electrical and compositional gradients begin to exert a much more important role on feature filling behavior.…”

Electroplating of Fe-Rich NiFe Alloys in Sub-50 nm Lines

“…9, 10 Kim et al further studied and adapted the same system for the electroplating of CuAg into trenches for improvements in the electromigration resistance. 11,12 The accelerating effect of KSeCN was only observed on Ag plating and no impact on Cu plating rate was observed. The super filling performance was improved and enabled by introducing an additional additive, thiourea, into the system, which was believed to slow down the surface mobility of the accelerating KSeCN and promote the CEAC behavior.…”

Accuracy Improvement in Cyclic Voltammetry Stripping Analysis of Thiourea Concentration in Copper Plating Baths

“…20,21,23,24 Various applications of TU as an additive have been studied, including the formation of the Cu twin, Ag superfilling, and the fabrication of CuS nanowire structures. 18,19,[23][24][25][26] TU is known to form thiolate complexes such as [Cu-(TU) ions. [27][28][29] Owing to the various derivatives and their different electrochemical responses, TU shows unique electrochemical behavior unlike typical suppressors or levelers.…”

“…1,2,[6][7][8][9][10][11][12][13][18][19][20][21][22][23][24][25][26][27][28][29] TU is a common additive in Cu and Ag electrodeposition baths and induces leveling and grain refining properties.…”

“…[18][19][20][21][22][23][24][25][26] TU has been used as an additive either solely or in combination with Cl − (TU-Cl − ) in baths used for electrodeposition processes involving various current/potential waveforms such as direct current, pulse-, or pulsereverse waveforms. 20,21,23,24 Various applications of TU as an additive have been studied, including the formation of the Cu twin, Ag superfilling, and the fabrication of CuS nanowire structures.…”