High-Aspect-Ratio Copper Via Filling Used for Three-Dimensional Chip Stacking

Abstract

Through-chip electrodes with high aspect ratios can offer the shortest interconnection and reduce signal delay. Copper has been selected as that electrode material because of its good compatibility to conventional multilayer interconnection in large-scale integration and back end-of-line processes. In this paper, filling vias with higher aspect ratio, 10 m 2 and 70 m depth, used for through-chip electrodes is reported. Removing overhang at via tops is important to achieve perfect via filling. Upon testing a series of electrodeposition conditions, conformal electrodeposits were obtained. With those conformal electrodeposits, seams and voids always remained at the via center. Perfect via filling was achieved by the pulse reverse plating method and by increasing Janus Green B concentration up to 20 mg/L in the plating bath.

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

“…In Fig. 1(a), copper deposition potentials at 10 mA/ * Corresponding author, E-mail: jhlee@hongik.ac.kr 2 were analysed with time. The addition of tetronic 701 increased the copper deposition overpotential.…”

“…One of the most promising technologies in 3D packaging is through silicon via (TSV). 1,2) It can achieve high density of packaging and minimize signal delay. Low electric resistance is achieved by interconnecting through via holes due to its short wire length.…”

“…It is also compatible with multilayer and back-end processes. [1][2][3] In this study, high aspect ratio via was lled by electroplating method. The inside of via hole should have no void or seams and it can be achieved by bottom-up deposition in ne trenches called super lling .…”

“…[6][7][8][9][10] However, the decomposition of these organic additives process have been known to cause contamination of bath. 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.…”

Polyquaternium-2: A New Levelling Agent for Copper Electroplating from Acidic Sulphate Bath

“…9 The addition of leveler, for example Janus Green B (JGB), can significantly enhance the performance of a plating formula because the forced convection acting on the board surface is always stronger than that at the middle of the TH during electroplating. 16,17 It is a very time-consuming work to search or design additives for TH electroplating. Until now, only few additives used for TH electroplating have been reported.…”