Inhibition of multi-site adsorption of polyethylene glycol during copper via-filling process

Abstract

The inhibitory effect of molecular weight (Mw) of polyethylene glycol (PEG) on the through-hole filling by copper electroplating was investigated by the electrochemical testing method and energy change with DFT. The cathodic polarization, electron transfer resistance, and diffusion coefficient of PEG with different Mw and concentration were assayed by cyclic voltammetry and electrochemical impedance spectroscopy; The inhibitory effect of different PEG Mw was demonstrated and examined by cross-sectional images using OLYMPUS confocal laser microscope, and the thickness of the copper layer and TP value were important measurement standards. The adsorption behavior on copper surfaces was calculated using the first principles. As PEG Mw and concentration are increased, the best TP value and diffusion coefficient of the plating formula is gained when PEG Mw and concentration are 20000 g/mol and 250 mg/L, they are 148.56% and 2.34 × 10-7, respectively. Better adsorption energy can be obtained as the adsorption sites of PEG increases, and the adsorption energy of PEG5 is − 1.99 eV. The experimental and theoretical results show that PEG with small Mw has no inhibitory effect, and even accelerates the deposition rate of Cu2+/1+. Only when the Mw and concentration exceed 2000 g/mol and 150 mg/L, PEG can inhibit the deposition of Cu2+/1+, and the best effect of through-hole electroplating is 20000 g/mol and 250 mg/L.