Investigation of Bis-(3-sodiumsulfopropyl disulfide) (SPS) Decomposition in a Copper-Electroplating Bath Using Mass Spectroscopy

Abstract

Bis-͑3-sodiumsulfopropyl disulfide͒ ͑SPS͒ is a well-known accelerator used to promote "bottom-up filling" in the semiconductor copper ͑Cu͒ electroplating process. However, the gap-filling capability and the defect performance of Cu electroplating are impacted as the SPS molecules are decomposed or oxidized. In this study, by-products generated from SPS decomposition and oxidation were identified and quantized using mass spectroscopy. It was found that 1,3-propanedisulfonic acid ͑PDS͒ was the most stable species among the SPS by-products. The PDS concentration increased with the increasing surface area of immersed Cu metals. The relationship between the consumption rate of SPS and the generation rate of PDS with different surface areas of Cu metals was particularly investigated. Furthermore, an equivalent circuit was developed and then examined using electrochemical impedance spectroscopy to characterize the properties of the aged bath with the decomposition of SPS.

Studies of Bis-(Sodium-Sulfopropyl)-Disulfide and 3-Mercapto-1-Propanesulfonate on/into the Copper Electrodeposited Layer by Time-of-Flight Secondary-Ion Mass Spectrometry

“…Molecular and elemental characterisation of compositions and its by-products in the electroplating bath were provided by mass spectroscopy [ 15 , 16 , 17 ], liquid chromatography mass spectrometry (LC-MS) [ 18 ], and high-pressure liquid chromatography (HPLC) [ 19 ].…”

Copper Electroplating with Polyethylene Glycol: Part II. Experimental Analysis and Determination of Model Parameters

“…Various analytical techniques, including cyclic voltammetric stripping (CVS), high-performance liquid chromatography (HPLC), and mass spectroscopy (MS), haven been applied to investigate the degradation of additives. [41][42][43][44][45][46] According to those studies, accelerator additives are less stable 41,[43][44][45] than suppressor additives. The concentration of the latter was found to be stable even after hundreds of hours of deposition under standard conditions.…”

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

“…The widely used additive bis-(3-sulfopropyl) disulfide (SPS) has been shown to decompose to 1,3propane 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). 32 In 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.…”