Influence of SPS Decomposition Product 1,3-Propane Disulfonic Acid on Electrolytic Copper Via Filling Performance

Abstract

Formation of interlayer connections in semiconductor and printed circuit board packaging can be accomplished by filling vias using three additive component electrolytic copper deposition. One of the essential additives that enables filling performance, bis-(3-sulfopropyl) disulfide (SPS) oxidized during electrolysis to give 1,3-propane disulfonic acid (PDS). In order to further elucidate the plating chemistry and improve performance, the electrochemical effects and the effects of PDS content in the electrolyte on resulting copper deposits were investigated. The crystallite structure and crystal structure transitions were investigated using X-ray diffractometry and the influence on physical properties of the deposit by internal strain analysis and extensibility. Combustioninfrared absorption spectrometry was used to determine the C and S content in the respective deposits. In all examinations, PDS content in the electrolyte was found to influence plating performance and deposit characteristics. The results suggested that PDS masked SPS and that co-deposition of PDS affected the deposit physical properties. In the late 1990s, package densification had been achieved by adoption of electrolytic copper sulfate via fill plating for interlayer connection in printed circuit board (PCB) manufacture. Since then, this technology has been used for fabrication of highly functionalized PCBs found in high-end electronic devices such as smartphones, and has been predicted to gain in importance. [1][2][3][4][5][6][7][8][9][10][11][12][13] The filling performance of the plating bath has been known to manifest from the action of organic additives.14-27 However due to additive decomposition, in industrial application periodic active carbon treatment and bath renewal is performed, where specifications have been determined by practical experience. With the more recent adoption of copper sulfate plating as an essential technology in semiconductor and high-end PCB manufacture, investigation of the bath aging phenomena and establishment of quantitative bath management methods may contribute to evolution of the technology.Due to the growing necessity for high performance via fill technology, decomposition mechanisms of the additives used in copper sulfate via fill plating and the effects of decomposition products on filling performance have been examined. The widely used additive bis-(3-sulfopropyl) disulfide (SPS) has been shown to decompose to 1,3-propane disulfonic acid (PDS) by oxidation during electrolysis. [28][29][30][31] Furthermore, detrimental effects of PDS on filling performance has been reported (Figure 1), where electrochemical analysis revealed that PDS countered the depolarizing effect of SPS on copper deposition (Figure 2). 32In consideration of the substantial influence of PDS on copper plating, analysis of the effects of PDS on the physical properties of copper deposits plated from baths containing PDS is necessary to achieve high performance from plating baths. To accomplish this, deposits from PDS containing baths we...

Effects of Leveler Concentration in High Aspect Ratio Via Filling in 3D SiP

“…1,2) This contamination problem can cause reliability problems in the devices and reduce the life time of the solution. 11,12) Therefore, an alternative plating process employing a plating solution which has lower additive concentration has been studied. [11][12][13][14][15][16][17] The objective of this study is to nd optimum leveler concentration to ll via without using accelerator and suppressor.…”

“…11,12) Therefore, an alternative plating process employing a plating solution which has lower additive concentration has been studied. [11][12][13][14][15][16][17] The objective of this study is to nd optimum leveler concentration to ll via without using accelerator and suppressor. In this study, accelerator and suppressor were not added to reduce the concentration of organic additives.…”

Observation of Bis-(3-sulfopropyl) Disulfide (SPS) Breakdown at the Cu Cathode and Insoluble Anode under Open-Circuit, Unpowered Closed-Circuit, and Electrolysis Conditions

“…Because of this, an aged electroplating bath results in defects or failure, such as a void (or seam) in a trench (or via) filling, rough surface, or pinhole. [17][18][19][20][21][22] To understand the origin of bath failure, the decomposition mechanisms of organic additives under open-circuit and electrolytic conditions have been studied in many papers. 23 Especially, SPS decomposition has been intensively studied, 16,[24][25][26][27][28][29][30][31] because it is most vulnerable under an electrolytic condition, and its breakdown product strongly influences bath performance.…”

The Degradation Behavior of Brightener on Dimensionally Stable Anodes during the Copper Electrodeposition

“…However, the brighteners, e.g., SPS, are usually troublesome because they are small molecules containing the active thiol group which is easily oxidized to form the oxygen-attached functional groups (e.g., sulfonate group). 6,23,31,32 Once the exposed thiol ligand is fully replaced with the inactive sulfonate group, the depolarizing ability of MPS/SPS completely disappears and the stable 1,3-propane disulfonic acid (PDS) is formed and accumulated in the plating bath. The presence of PDS slightly increases the overpotential of Cu deposition and causes the detrimental filling result if its concentration is too high.…”