Investigation of Working Mechanism of Bis-(3-sulfopropyl) Disulfide (SPS) during Cu Electroless Deposition Using Real-Time Observation Method

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.

Section: Interaction Mechanism Of the Accelerators With CL − And Peg ...mentioning

confidence: 99%

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

Luo¹,

Li²,

Shi³

et al. 2019

“…39 Upon the addition of formaldehyde the potential of the WE reaches −0.86 V, consistent with prior literature where potentials are reported between −0.8 and −0.95 V depending on pH and complexing agent. 1,8,[31][32][33][34][35]40,41 The −0.86 V is more positive than the potentials reached in the case of BP. The change in potential, −0.5 V, with formaldehyde addition, however, is similar to that seen with BP.…”

Section: Resultsmentioning

confidence: 73%

“…−0.3 to −0.5 V upon the addition of a complexing agent. [31][32][33][34][35] The drop is associated with the dissolution of Cu/Cu oxides yielding more Cu(0) at the electrode surface and is dependent on the complexing agent and amount of oxidation. 33 A negative shift in the Cu reduction potential from complexation may also contribute to the drop in potential.…”

Section: Resultsmentioning

confidence: 99%

Effect of Ni on Electroless Cu Plating Rates in the Presence of 2,2′-Bipyridyl and 2-Mercaptobenzothiazole

Lindsay,

Rohde,

Bernhard

et al. 2023

Electrochemical measurements and Surface Enhanced Raman Spectroscopy (SERS) are used to evaluate the effect of Ni addition on the rate of Cu electroless deposition in the presence of 2,2′-bipyridyl (BP) and 2-mercaptobenzothiazole (MBT). Ni addition is found to increase the rate of electroless Cu deposition in the presence of BP but had no effect on the rate in the presence of MBT. In situ SERS obtained at the potential of electroless deposition shows that BP is destabilized from the Cu surface in the presence of Ni, likely due to the increased positive charge present with Ni-incorporated Cu. The BP deficient surface exhibits a higher electroless deposition rate relative to a surface with substantial BP. In contrast, SERS shows that Ni addition does not alter MBT adsorption to Cu, due to the increased affinity of MBT to the electrode surface relative to BP.

“…It can be seen that bottom-up filling occurred in the microvias by using MPS as the accelerator, which was in accordance with the reported literatures. 10,32 When DMPS was used as the accelerator, the deposited copper layer on the surface was thicker than that obtained at the bottom of the microvia which means DMPS showed a bad filling performance in such conditions. However, the accelerating effect of DMPS on copper deposition was much stronger than that of MPS.…”

Section: Resultsmentioning

confidence: 99%

“…[6][7][8][9] One of the functional additives was accelerator, which was usually small organic molecules containing sulfur atom, such as 3mercapto-1-propanesulfonate (MPS) and bis-3-sulfopropyl-disulfide (SPS). 3,10,11 According to convection-dependent adsorption (CDA) mechanism, accelerator molecules mainly adsorbed at the bottom of the microvia due to the weak convection there. 12,13 As a result, the copper deposition inside the microvia was greatly accelerated, which finally led to bottom-up deposition.…”

mentioning

confidence: 99%

Function of Sulfhydryl (–HS) Group During Microvia Filling by Copper Plating

Zhao¹,

Pang²,

Wang³

et al. 2020

In this work, 3-mercapto-1-propanesulfonate (MPS) with one sulfhydryl (-HS) group and 2,3-dimercapto-1-propanesulfonate (DMPS) with two -HS groups were used as model additives to reveal the function of -HS group during copper plating. Chronopotentiometry was employed to characterize the different electrochemical behaviors of the two model additives. It indicated that DMPS showed stronger accelerating effect than MPS in the plating bath containing Cl − , which could be attributed to its enhanced adsorption caused by two -HS groups. The pre-adsorption and desorption experiments demonstrated the synergistic effects and competitive adsorption between Cl − and the model additives. Moreover, the accelerating mechanism was investigated by cyclic voltammetry combined with rotating ring-disk electrode (RRDE), demonstrating MPS could accelerate the ratedetermining step (RDS) of copper deposition only if Cl − was present, whereas DMPS could enhance the RDS whether Cl − existed or not. Finally, microvia filling experiments were carried out to evaluate the filling performance of the two model additives. The results indicated that in the plating bath containing PEG and Cl − , MPS showed good filling performance, while DMPS did poorly. However, after the introduction of JGB, the filling performance of DMPS was greatly improved, which was resulted from the competitive adsorption between DMPS and PEG being balanced by JGB.