Raman Spectroscopy And Electrochemical Study On Adsorption Behavior Of Nitrogen-containing Additives In Acidic Solution On Copper Electrode Surface

Additive is a key factor in the copper electroplating process,the addition of organic or inorganic additives can cause significant changes in the coating,such as improved brightness,smoothness,hardness and ductility.Various additives synergize with each other but compete with each other,and the combination of additives with appropriate concentration can ensure good electroplating performance.This paper mainly studied the adsorption behavior of organic additives on the surface of copper electrodes by in-situ Raman spectroscopy,and illustrated the role of additives in the electroplating process through actual copper electroplating experiments,so as to provide theoretical guidance for the application and development of additives.The specific research contents were as follows:1.Adsorption behavior of thiourea（TU）on the surface of copper electrodeThiourea was mainly adsorbed on the surface of the copper electrode by sulfur atoms and-NH₂.It not only can adsorb on the surface of the electrode to inhibit the reduction of copper ions,but also have a strong complexation with Cu²⁺and Cu⁺.The formation of the complex can effectively reduce the rate of electron reduction of Cu²⁺to copper,and can also inhibit the disproportionation reaction of Cu⁺in the acid copper plating system,preventing the direct nucleation and reduction of Cu⁺to copper.In addition,it is found that thiourea and its complex will preferentially adsorb on the convex part of the uneven copper surface,which can hinder the copper electrodeposition in this area.2.Adsorption behavior of crystal violet（CV）on the surface of copper electrodeCrystal violet molecules showed different adsorption modes under different voltages,mainly in the form of lying on the copper electrode surface.It has a strong adsorption effect on the current density during copper deposition,and inhibits the reduction of Cu²⁺.Moreover,the adsorption mode of crystal violet has an obvious process of first adsorption and then desorption with the negative shift of the potential.3.Adsorption behavior of benzotriazole（BTAH）,sodium 3-mercapto-1-propanesulfonate（MPS）and Cl^-on the surface of copper electrodeBTAH has a strong adsorption effect on the copper electrode surface,which affects the deposition potential of copper.The presence of MPS and Cl^-at the same time show the role of promoting copper deposition.Raman spectroscopy experiments proved the strong adsorption of BTAH,and it is mainly in the form of Cu（I）BTA polymer adsorption at the vicinity of the relatively positive voltage,while in the form of BTAH molecular adsorption at the negative voltage region.MPS is mainly adsorbed on the copper electrode surface with thiol end.When BTAH,MPS and Cl^-exist at the same time,the strong adsorption of BTAH dominates,but MPS still occupies part of the active sites on the surface to synergize with Cl^-,thereby locally promoting copper electrodeposition.