Effects of Accelerator Alkyl Chain Length on the Microvia Filling Performance in Copper Superconformal Electroplating

Abstract

In addition to the commercialized accelerator bis-(sodium sulfopropyl)-disulfide (SPS), we designed and synthesized two other disulfide compounds, namely, bis-(sodium sulfohexyl)-disulfide (SHS) and bis-(sodium sulfoethyl)-disulfide (SES), to investigate the effect of their alkyl chain lengths on the microvia filling performance. The galvanostatic measurements show that the addition of Cl − to different accelerator-containing solutions leads to the same synergistic effects at a current density of 20 mA/cm 2 , indicating that the interactions between accelerators and Cl − are independent of their alkyl chain lengths. However, when both Cl − and a suppressor are present, the alkyl chain length in accelerators strongly impacts their anti-suppressor strength, which increases with the growth of the alkyl chain length, reaches a maximum (SPS) and then decreases. A possible adsorption and interaction model was proposed to explain the difference of anti-suppressor effects, and microvia filling plating experiments were carried out to evaluate the effects on the filling performance. It was found that both SES and SPS, which have appropriate molecular lengths and relatively strong antagonistic effects against polyethylene glycol (PEG) and Cl − ensemble, achieved complete microvia filling. For SHS, due to the overlong alkyl chain and weak antagonistic effect against PEG and Cl − , no microvia was completely filled.

Interaction of Bis-(sodium-sulfopropyl)-Disulfide and Polyethylene Glycol on the Copper Electrodeposited Layer by Time-of-Flight Secondary-Ion Mass Spectrometry

“…The electrochemistry of PEG-Cl-SPS has been studied thoroughly [ 5 , 44 , 45 , 46 ]. Unfortunately, there is still a limited number of appropriate experiments oriented toward the combination of cyclic voltammetry experiments with a modern spectroscopic technique that is useful for resolving the interaction of PEG/SPS/Cl.…”

Effects of DPS on Surface Roughness and Mechanical Properties of Electrodeposited Copper Foils

“…[ 40,41 ] This structure's bending and rotating properties can effectively bring the Cu + in solution closer to the electrode surface for achieving rapid discharge and the accelerated deposition of copper. [ 42 ]…”

“…[40,41] This structure's bending and rotating properties can effectively bring the Cu + in solution closer to the electrode surface for achieving rapid discharge and the accelerated deposition of copper. [42] As shown in region-III of Figure 2, the reduction peak potential negatively shifted by about 134 mV after adding HAP compared with VMS curve a, indicating the strong inhibitory effect of HAP. The positive shift of the reduction peak was about 32 and 34 mV after the addition of HP and DPS, respectively.…”

Novel, Simple, and Green Citrate-Based Copper Electronic Electroplating Bath in Microvia Void-Free Filling for Printed Circuit Board Application

“…Owing to the uneven local current contribution, the deposition rate of copper at the mouth is generally higher than that at the bottom of the microvia, resulting in quick sealing of the mouth or the formation of voids. To achieve void-free filling, a high concentration of copper ions and kinds of additives (such as a suppressor, accelerator, and leveler) in low concentration (less than 100 mg/L) are needed. − It can be easily found that the additives and their concentrations are very hard to regulate due to their different consumption rates and complicated synergistic effects. Besides, the high concentration of sulfuric acid is corrosive to equipment.…”