Zhao-Yun Wang,Lei Jin,Guang Li,Jia-Qiang Yang,Wei-Qing Li,DongPing Zhan,Yan-Xia Jiang,Fang-Zu Yang,Shi-Gang Sun
An organic additive, gentian violet (GVT), is explored for the first time as a novel leveler with excellent property in through-holes (THs) metallization of Cu electronic plating in acidic medium for printed circuit board (PCB) applications. Studies of galvanostatic measurements with a platinum rotation disk electrode and density functional theory calculations demonstrate that the GVT behaves the fundamental leveler's characteristics of mass transfer adsorption, and displays a strong inhibition effect on electro-reduction of cupric ions at high rotating rate. Although the adsorption ability of GVT on Cu surface is weaker than that of commercial leveler Janus Green B (JGB), the potential difference of cupric ion reduction between low and high rotating rates is larger in case of GVT than that of JGB at same current density. Cyclic voltammetry measurements indicate that the Cu amounts of cathodic deposition and that of anodic stripping tend to the same at both low and high rotating rates when GVT, Cl − , polyethylene glycol (PEG) and bis-(sodium sulfopropyl)-disulfide (SPS) coexist in the solution, demonstrating excellent synergistic action of these additives and super leveling effect. In situ FTIR spectroscopic analysis combined with cyclic voltammetry measurements illustrate that the GVT adsorbs on Cu surface and thus affects the electro-reduction of cupric ions, which reveals the very complicated synergistic actions of these additives, i.e., the adsorption ability of GVT can be slightly enhanced by Cl − , while it has been greatly enhanced in the presence of PEG which nevertheless decreases slightly the inhibition effect of PEG on electro-reduction of cupric ions; the SPS plays an antagonistic effect with GVT due to their competitive adsorption. Based on the characterization of GVT as a novel leveler, we developed a GVT-based formula of THs metallization of Cu electronic plating, and demonstrated an excellent efficiency of a throwing power of 97.6% at 10 mA·cm −2 in a real PCB THs metallization of Cu electronic plating.
Ke Li,Qifei Xia,Lei Jin,Rongbin Xu,Yi Zhong,Daquan Yu
Leveler additives for Cu electrodeposition are critical for achieving bottom-up filling in micrometer scale and high aspect ratio (AR) through-silicon vias (TSVs). This study explores a highly effective imidazolium-based leveler electroplating formulation, which successfully achieves void-free filling of TSVs with a diameter of 3 μm and a depth of 45 μm (with an ultra-high AR of 15:1). Molecular dynamics simulations reveal that the leveler, 1,2-dimethyl-3-propylimidazolium iodide (DMPII), demonstrates a strong adsorption effect on the Cu surface. Electrochemical tests show that DMPII enhances the inhibitory effect of polyethylene glycol (PEG) while simultaneously amplifying the accelerating effect of bis-(sodium sulfopropyl)-disulfide (SPS). The complex interplay among these additives ultimately leads to a significant inhibitory effect on the electrochemical reduction of Cu ions at the TSV sidewalls, while promoting deposition at the bottom of the TSV. Furthermore, minimal impurities are detected in the electroplated Cu layer. These findings suggest that this DMPII-based electroplating formulation holds significant promise for the fabrication of ultra-high AR TSVs to enable future high-density 3D integration.
Tao Song,Zhao-Yun Wang,Jia-Qiang Yang,Yi Zhao,Fang-Zu Yang,Dongping Zhan
A phosphorus-containing new compound of tributyl(hexyl)phosphonium chloride (TBHP), but not the commonly used nitrogen-containing heterocycles and quaternary ammonium salts, is successfully applied for the superconformal copper filling of microvia in acid sulfate electroplating bath for the application of electronic industry. The molecular interaction mechanisms of TBHP combined with suppressor (polyethylene glycol, PEG) and accelerator (bis-(sodium sulfopropyl)-disulfide, SPS) are investigated in detail. Galvanostatic measurements at platinum rotation disk electrode indicate that the leveler of TBHP among with the suppressor and accelerator behaves the key characters of inhibition and convection-dependent adsorption during copper ions electroreduction for the bottom-up filling of microvia. Cyclic voltammetry measurements and in-situ FTIR spectroscopy further reveal that TBHP synergistically interacts with the suppressor to inhibit copper ions electroreduction at the mouth of microvia; while TBHP competes for adsorption with the accelerator, behaving as TBHP gradually replaced by the accelerator at the bottom. Based on the sufficient theoretical supports, the practical copper electroplating is conducted for the verification of microvia void free filling. In the developed novel copper plating formula containing TBHP, PEG and SPS, the void free filling is successfully achieved and the filling percentage (FP) is high in 95.5%.
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