The Electrodeposition Conditions of Functional Gold Films for Microelectronics

Abstract

The morphology and physico-mechanical properties of electrodeposited gold films have been studied. The electrodeposition was performed in the phosphoric bath. The formulation and deposition condition were following: 0.05M KAu(CN)2 + 0.25M (NH4)H2HPO4 + 0.40M (NH4)2HHPO4 without and with additives of surfactants, namely 10 mg l–1 oxyethylendiphosphoric acid (H4OEtDP) + 0.75 mg l–1 cyanethilendiamine (CyEn), at pH 5.6, 60 – 70 °C and current density 0.2 – 0.6 A dm–2. The morphology of obtained films was studied by means of SEM, and texture of obtained films on a brass substrate was studied by means of X-ray diffractometry. The gold films consist of crystallites which size varies 0.8 to 1.6 μm. Correlation between texture and mechanical stresses in the deposits is discussed.
The physico-mechanical properties (internal stress, porosity, microhardness) of gold coatings electrodeposited from the phosphoric acid bath on the brass substrate depend on current densities and strongly correlate with their morphology.
The adding of H4OEtDP and CyEn into phosphoric gilding bath enables to obtain the gold films possessing reasonable properties for the microelectronics application in wider range of current densities (up to 0.6 A dm–2).