Detection of Cuprous Ions By Micro Ring Electrodes on a TSV Side Wall

Abstract

Copper electrodeposition in through silicon via (TSV) occurs in two steps with the intermediate is cuprous which has a certain role in filling of the TSV. The inhibition of the TSV outside is not only by inhibitors but also by the dispersion of cuprous complexes. Further, cuprous complexes remain inside of the via are almost deposited, and contribute to the acceleration of the via bottom filling. In this research, micro ring electrodes were made using silicon processing (Fig. 1). Five 5x5µm size micro electrodes, which were formed by platinum sputtering on a silicon substrate, have 10µm pitch. The microelectrodes were wired out. A SiO2 layer was covered over wires and left a 10x50µm space on the microelectrodes. A silicon substrate cap has a groove, size of 10µm width, 10m height and 50µm depth, was sputtered copper then it was pronated on the micro electrodes. Electrolyte baths using in the experiments contained 200g/L Cu2SO4.5H2O and 25g/L H2SO4 and were added additives depending on measurements. The cap was the disk electrode working at -50mV vs SCE, the micro platinum electrodes connected to a switch which wired to the ring cable of a potentiostat/galvanostat working at 500mV vs SCE. The disk currents were stable and the value was in the range -2µA to -3µA. The ring current was in the range of 0.2nA to 0.5nA. Measurement of three electrodes E1, E3, E5 showed that the ring current was highest at the electrode E5 without additives, however, in the present of Clˉ and SPS the electrode E1 had the highest current. Figure 1