Bis-(sodium sulfoethyl)-disulfide: A Promising Accelerator for Super-conformal Copper Electrodeposition with Wide Operating Concentration Ranges
Zhen Li, Baizhao Tan, Minghao Shi, Jiye Luo, Zhifeng Hao, Jun He, Guannan Yang, Chengqiang Cui
Abstract
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 Δ η , 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.