Highly corrosion resistant bright silver metallization deposited from a neutral cyanide-free solution

In this paper, we describe a new method for preparing the high-quality silver films that can be used for packaging level interconnects. Silver has excellent optical and electrical properties but its application in microelectronics is compromised due to its tendency to sulfide corrosion. Another problem is hazardous cyanide electrolytes/bath technology that has to be improved. We present bright silver films obtained by electrodeposition from near to neutral non cyanide solution. High corrosion resistance was achieved by Ag protection with organic SAMs. The SAM protection power was quantified by comparison of para-amino phenol (PAP) peak current decrease in Cyclic Voltammetry (CV) and the Electron (charge) Transfer Resistance (CTR) increase from Electrochemical Impedance Spectroscopy (EIS). The accelerated tarnishing tests in H2S atmosphere well support the electrochemical test results.

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► Mirror bright Ag coatings from neutral non cyanide 4-component electrolyte.
► Organic SAMs (thiols) increase Ag corrosion resistance by a factor of hundreds.
► Methods for SAM protective power quantification – Cyclic Voltammetry and Electrochemical Impedance Spectroscopy.
► Both CV and EIS support that region between n = 9 and 11 is critical in crumbly to dense SAM transition.
► While T-8 still presents poor barrier, T-12 and, especially, T-18 provide excellent corrosion protection.