Electrodeposition of Ni-W alloy inside trench by current modulation

초록

In recent years, much attentiion has been paid to MEMS( Micro Electro Mechanical Systems ) and deposition of metal into vias or trenches is one of the important fabrication processes for making the mechanical elements of MEMS device. And electrodeposition has important advantages over alternative techniques, such as the high deposition rate,the easy control for thickness and low cost. Especially, Ni-W alloy electrodeposition might have some excellent properties such as high hardness, high corrosion resistance and high thermal stability. Filling phenomena of Ni-W electrodeposition are strongly influenced by the current density and the current waveform. Better filling phenomena are observed with increasing current off time in PC plating because of decreasing concentration gradient between top and bottom in trench. This work is aimed to investigate the effect of pulse current on Ni-W alloy electrodeposition to fill trench with aspect ratio 1:2 for MEMS applications. Various pulse current conditions were used to investigate the properties of nanocrystalline Ni-W electrodeposits. Current densities were controlled by potentiostat & galvanostat and various pulse times and duty cycles were applied by the function generator. Energy dispersive X-ray spectroscopy was used to analyze elemental compositions of the Ni-W alloys. Structural analysis of the deposits was performed by means of X-ray diffraction(XRD) and scanning electron microscopy(SEM).