Trench filling을 위해 사용된 Pulse current에 의해 증착된 Ni-W의 물성 연구

초록

In recent years, much attention has been paid to MEMS(Micro Electro Mechanical Systems) and deposition of metal inside vias or trenches becomes the important fabrication processes for making the mechanical elements of MEMS device. Electrodeposition has several advantages over alternative techiques, such as the high deposition rate, the easy control forthickness and low cost. Ni-W alloy has distinct properties of highhardness, high corrosionresistance and high thermal stability. Filling phenomena of Ni-W electrodeposition are strongly influenced by the current density and the current-off time. Better filling phenomena are observed with the increase of current-off time due to the decreasing concentration gradient between top and bottom in trench. In this work, we investigated the effect of current pulse waveform on Ni-W alloy electrodeposition to fill trench with aspect ratio 1:2 for MEMS applications. Applied current density, pulse time, and duty rtios affect the filling morphology inside trenches and optimum superfilling conditions were actively sought. Current densities were controlled by an EG＆G PAR273A potentiostat ＆galvanostat and various pulse times and duty cycles were superimposed with the function generator. Energy dispersive X-ray spectroscopy(EDS) 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).