Leveling of Microvias by Electroplating for Wafer Level Packaging

Abstract

The filling of microvias with diameters between 30 and 100 µm and aspect ratios up to 2.5 in silicon wafers, was investigated to determine the performance of copper electroplating. An electrolyte with a low leveler concentration was only suitable for filling microvias with aspect ratios below 1. An increase of the leveler concentration enabled the filling of microvias with higher aspect ratios. The fill-up evolution shows a bottom-up plating behavior. Electrochemical measurements show that for conditions prevailing at the bottom of the via, the electrodeposition rate is enhanced while for conditions prevailing at the top, it is inhibited. This difference originates from a concentration gradient of leveler inside the via and different convection conditions inside and outside the via.

Potential Oscillations in Galvanostatic Cu Electrodeposition: Antagonistic and Synergistic Effects among SPS, Chloride, and Suppressor Additives

“…Janus Green B (JGB), − a prototypical monomeric leveler of low molecular weight, produces copper films with a contamination level that is significantly higher than the one reported in the present study (see Supporting Information). The leveling concept of JGB makes particular use of such a consumptive inclusion into the deposit in combination with mass transfer effects as crucial prerequisite for its mode of action, e.g., in context of the 3D-TSV copper plating. ,, Electroplated copper films typically undergo a postdeposition self-annealing even at room temperature with an actual self-annealing rate that was discussed to depend on the overall contamination level in the copper deposit …”

“…The leveling concept of JGB makes particular use of such a consumptive inclusion into the deposit in combination with mass transfer effects as crucial prerequisite for its mode of action, e.g., in context of the 3D-TSV copper plating. 19,53,56 Electroplated copper films typically undergo a postdeposition self-annealing even at room temperature with an actual self-annealing rate that was discussed to depend on the overall contamination level in the copper deposit. 19 In order to correlate the oscillatory behavior seen in the chronopotentiometry and the SIMS with the resulting film morphology, we performed complementary FIB experiments.…”

Copolymers of Imidazole and 1,4-Butandiol Diglycidyl Ether as an Efficient Suppressor Additive for Copper Electroplating

“…It is used in context of the socalled Damascene process 1,2 and in the upcoming Through-Silicon-Via (TSV) technology [3][4][5] to build up interconnect architectures in logic and memory devices. 6,7 For the defect-free bottom-up fill of trenches and vias, one has to deposit the copper in the presence of particular plating additives. It is their sophisticated interplay that suppresses copper growth on the wafer surface and upper side-walls of those features whereas the copper deposition is accelerated at the bottom of those features.…”

Influence of Aromatic Functionality on Quaternary Ammonium Levelers for Cu Plating

“…22,23 Lu ¨hn, et al determined that the concentration gradient of the leveler along the via profile is important for achieving complete fill. 24 Kim and coworkers showed that the chain length of the leveler aliphatic tail and counter ion can influence the effectiveness of the suppression layer formed by the leveler. 11 Several studies examine methods to minimize defects in the Cu electrodeposit by varying electrodeposition pulse time, current density and additive concentrations.…”