Special electrochemical behaviour of sodium thiazolinyl-dithiopropane sulphonate during microvia filling

In this work, galvanostatic measurements were employed to study the electrochemical behaviour of thiazolinyl-dithiopropane sulphonate (SH110) in a copper plating process, which indicated that it had a critical concentration of 12.5 mg L−1. At this critical concentration, it would accelerate copper deposition at strong forced convection but inhibit copper deposition at weak forced convection. To get more insight into SH110, its potential decomposition products, 3-mercapto-1-propanesulphonate (MPS) and 2-thiazoline-2-thiol (H1), were also investigated. It was found that MPS always presented an acceleration effect with its concentration increasing, whereas H1, with a simple molecular structure, also had a critical concentration, which was 1.25 mg L−1. As expected, superfilling can be achieved by using H1 as the single additive. Finally, the interaction between SH110 and H1 was studied to prove the decomposition of SH110, as well as to illustrate its action mechanism.