Bis-(sodium sulfoethyl)-disulfide: A Promising Accelerator for Super-conformal Copper Electrodeposition with Wide Operating Concentration Ranges

Accelerators are indispensable additives for super-conformal copper electrodeposition, which has been widely applied in the fabrication of integrated circuits (ICs), printed circuit boards (PCBs), and advanced semiconductor packaging substrates. Currently, bis-(sodium sulfopropyl)-disulfide (SPS) and sodium 3-mercapto-1-propanesulfonate (MPS) are the most widely used accelerators for super-conformal electroplating. However, owing to the limited operating concentration range, frequent measurements of the SPS (or MPS) concentration during the electroplating process are needed to manage the accelerator concentration in a suitable range, which makes the application of SPS (or MPS) tedious and unreliable. In our previous study, bis-(sodium sulfoethyl)-disulfide (SES), which has a molecular structure that is similar to that of SPS but with shorter alkyl chains, was determined to be a weaker depolarizer than SPS. The weaker antagonistic effect against suppressor and leveler imply that the higher concentration of SES maybe applicable to achieve the super-conformal electroplating. In this study, SES was investigated in detail, and it was found that in combination with Cl−, PEG, and JGB, the SES-containing electrolytes can provide the positive potential difference Δη, excellent microvia filling performance, and good copper deposition physical properties in a wide operating concentration range. SES is a promising accelerator for the super-conformal copper electroplating.