Electrochemical Behavior of 2M5S and Its Influence on Reduction of Cu Pumping and Keep-Out Zone

Abstract

Previously, we have reported the low thermal expansion copper electrodeposited in solution containing 2-Mercapto-5benzimidazolesulfonic acid sodium salt dihydrate (2M5S). In this research, we investigated the electrochemical behavior 2M5S additive by CVS and LSV measurements. The 2M5S additive showed an inhibition effect during electrodeposition of copper, both in the absence and presence of Cl − . Using a combination of the 2M5S leveler with another SDDACC leveler and SPS accelerator, the thermal expansion of copper was reduced and the TSV was filled without defects. The SEM results showed that the copper pumping height of low TEC copper in PECVD SiO 2 TSV was only 0.5 μm. Meanwhile, the copper pumping height of reference conventional copper in PECVD SiO 2 TSV was about 2 μm. Furthermore, compared with thermal stress curve in Si around the conventional copper TSV, thermal stress curve in Si around the low TEC copper TSV was much lower and the KOZ also was reduced to about 1 μm.

Communication—A Rotating Ring Disk Study to Monitor the Concentration of 2M5S in Copper Low TEC Electrolytes

“…The study of the electrochemical behavior of 2M5S by V. Q. Dinh showed that 2M5S inhibits the copper deposition both in the absence and presence of Cl − . 8 However, in this case, the PEG inhibition effect is much stronger and suppresses the inhibition effect of 2M5S.…”

“…Dinh and K. Kondo. 1,8 They successfully reduced the TEC of copper from 17.2 × 10 −6 °C−1 to 14.5 × 10 −6 °C−1 by using 2 levellers sulfonated diallyl dimethyl ammonium chloride copolymer (SDDACC) and 2M5S. The reduction in copper TEC is explained by the incorporation of 2M5S into the electrodeposited copper.…”

“…The reduction in copper TEC is explained by the incorporation of 2M5S into the electrodeposited copper. 8 However, because of the incorporation, 2M5S is consumed during the copper electrodeposition. This consumption is the main reason for the deterioration of the electrodeposition solution for low TEC copper in which the low TEC electrolytes contain Cl − , SDDACC, 2M5S, and some other additives.…”

“…This consumption is the main reason for the deterioration of the electrodeposition solution for low TEC copper in which the low TEC electrolytes contain Cl − , SDDACC, 2M5S, and some other additives. 1,8 Besides the reduction of copper TEC, 2M5S is also used to modify other physical and mechanical properties of electrodeposited copper. 9,10 K. Yamanishi used 2M5S to increase the tensile strength of copper foil.…”

“…Because of several applications to improve copper properties, there have been studies investigating the electrochemical behaviour of 2M5S. 8,10,11 However, no one has attempted to determine the consumption amount of 2M5S in the electrodeposition solution.…”