Development of Measurement and Analysis System for Electrolytic Current and Application to Multilayer Electrodeposition with a Coulomb Controller

Abstract

In order to investigate the growth processes of nanometric multilayers electrodeposited using the single bath technique, we have developed a system that provides high-speed and high-resolution measurement and analysis of long time current. An attempt was made to analyze the current during Co-Cu/Cu multilayer electrodeposition using this system. Multilayers were electrodeposited using the single bath technique under potential control with a coulomb controller, and the target thickness of each layer (5 nm) was controlled according to the quantity of electricity. During electrodeposition of approximately 25 min, the current was measured every 0.1 ms and analyzed. Cross-sectional observation by field emission-scanning electron microscopy (FE-SEM) showed a multilayered structure of which the layer thicknesses were close to 5 nm. The quantities of electricity used for each layer were controlled exactly; however, the deposition times used varied for each Cu layer. The deposition time for each of the Co-Cu layers was constant; however, the current during each Co-Cu layer deposition was found to increase slowly. During electrodeposition, current peaks caused by overshooting were observed at every switching of the substrate potential. The estimated non-faradaic current included in the peak was sufficiently small with respect to a 5 nm layer thickness.