Prediction and Effect Verification of Thiamine as a Leveling Agent in Chip Wafer Electroplating

Thiamine, a nitrogen-containing heterocyclic compound, is explored for the first time as a novel leveling agent in this study. Based on the density functional theory (DFT) calculations and molecular dynamics (MD) simulations of the adsorption process of thiamine and the commonly used leveling agent JGB, the average values of the binding energies after equilibrium of thiamine and JGB are similar, which indicates that the thiamine molecules have strong bonding ability with the surface of copper and can be adsorbed tightly on the surface of copper. By cyclic voltammetry (CV) curve, thiamine was found to inhibit copper deposition and the inhibition effect was stronger than JGB. The chrono potential curve (CP) test found that the potential difference △η = 87 > 50 mV at high and low speeds of thiamine, which indicates that thiamine has the potential to be used as a leveling agent. Electrochemical impedance spectroscopy (EIS) testing found that thiamine inhibited copper precipitation by inhibiting the reactions of Cu2+ → Cu+ and Cu+ → Cu. According to electroplating experiments, thiamine has a leveling effect on wafer electroplating and can be used as a leveling agent because the copper layer on the wafer obtained by adding it has a smoother surface compared to the copper layer obtained without adding it. It was found that wafer electroplating does not require PEG, and only adding 55 mg/L Cl–, 6 mg/L SPS, and 4 mg/L thiamine as additives can achieve a good filling effect.