Structural and morphological characteristics of nanocrystalline copper electrodeposits from acid sulphate electrolytes

Abstract

Copper is the presently favoured and future interconnect material in high-end microprocessors and memory devices because of its low electrical resistivity and higher electromigration than aluminium. The present investigation deals with the electrodeposition of nanocrystalline copper onto brass metallic foil from electrolytes containing copper sulphate (CuSO₄·5H₂O) as the source of metal ion and sulphuric acid (H₂SO₄). Benzotriazole (0.5 g L^− 1) and sodium lauryl sulphate (0.1 g L^− 1) were used as additives. The electrolyte was mechanically agitated and the temperature was maintained at 3°C ± 2°C. These additives have been found to be effective in reducing the grain size, grain boundaries and improving surface morphology of the copper films. They also improve the throwing power of the deposition electrolytes and hardness of deposits. X-ray diffraction (XRD) patterns obtained for the electrodeposited copper films showed polycrystalline cubic structure. The crystal size of the copper films was calculated by both XRD and atomic force microscopy (AFM) analysis. A uniform and pore free surface morphology was observed under SEM, and AFM investigation revealed the grain refining brought about by the additives.

Keywords:

• Additive
• Atomic force microscopy
• Copper electrodeposition
• Nanocrystalline
• SEM analysis
• XRD studies