Plating Uniformity of Bottom-up Copper Pillars and Patterns for IC Substrates with Additive-assisted Electrodeposition

Abstract

Electrochemical behaviors of the base electrolyte containing different additives were investigated by galvanostatic potential transient measurements (GM), cyclic voltammetry tests (CV) and potentiostatic measurements. Copper deposits on sputtering copper seed from physical vapor deposition (PVD) were examined by a scanning electron microscope and X-ray diffraction spectra. Cross sections of copper pillars and fine line patterns were observed by metallographic microscope. GM result revealed ethylene oxide-propylene oxide co-polymer (EO/PO) performed a further inhibition on copper deposition in the presence of 60ppm chloride ions as the increment of EO/PO concentration. GM, CV and potentiostatic results indicated that copper deposition was accelerated by synergetic effects of additives in the base electrolyte containing 60ppm chloride ions, 20mg/L EO/PO and 0.7mg/L bis-(sodium sulfopropyl)-disulfide. Sputtering PVD copper seed with even deposit surface was recommended to form the uniformity of copper deposition through increasing the growing density of copper particles. Oscillatory was employed to form uniform distribution of copper deposits in thickness. Copper grain growth was preferentially [111] textured. Bottom-up copper pillars and fine line patterns with plating uniformity were fabricated to meet the requirement of an accurate impedance and the high density interconnection for IC substrates.