QCM Analysis of the Deposition Process in the Presence of the Additives for Copper Foil

Abstract

The copper film electrodeposited from the bath in the presence of some sort of additives such as brightener like Bis-(3-sulfopropyl)-disulfide (SPS) shows the decrease of Vickers hardness and tensile strength during keeping it even at room temperature. We have already reported that 2-Mercapto-5-benzimidazole (2M-5S) had the effects for preventing such a property change. In this report the incorporation processes of above additives were investigated under various electrolytic conditions by use of Quartz Crystal Microbalance (QCM) Method. The incorporation process depended on their electrolytic conditions. That is, under the electrolytic condition in the case of high concentration of all bath components and high current density and vigorous stirring of the bath, the incorporation process of the additives under linear sweep voltammetry mode was slightly different from that under the electrolytic condition in the case of low concentration of all bath components and low current density and no stirring of the bath.

Sulfur-Containing Additives for Mitigating Cu Protrusion in Through Silicon via (TSV)

“…11 However, this inhibition effect was weakened by the addition of 2M5S, which is known to form a complex layer (Cu(I)-2M5S) on the Cu surface by combining with Cu ions. 27,29,30 The formation of Cu(I)-2M5S is accelerated by iodide ions, as shown in the following reaction steps, 30 and accompanies the dissolution of the CuI inhibition layer, increasing the reduction current.…”

“…It is well known that, during Cu electrodeposition, 2M5S adsorbs strongly on the Cu surface and is incorporated into the Cu. 27,29 This process is accelerated by the catalytic effect of iodide ions. 30 The incorporated 2M5S induced a pinning effect, effectively mitigating Cu protrusion.…”

“…27 However, the sulfurcontaining additives with N atoms are strongly adsorbed on the Cu surface, and is known to accumulate at high levels in the Cu matrix. 27,28 These Impurities accumulated in the Cu grain boundaries, causing a so-called pinning effect 21,27,29,30 that inhibits the grain growth of Cu. To incorporate impurities into Cu-TSV, 2-mercapto-5-benzimidazole sulfonic acid (2M5S) and thiourea (TU) were additionally used during the TSV filling with iodide ions, which are an inorganic leveler.…”