XPS analysis of the interface between CVD-W and aluminum underlayer

This paper reports x-ray photoelectron spectroscopy (XPS) analysis of the interface between CVD-W and aluminum performed to examine the feasibility of selective tungsten plug for via-filling application. Tungsten was deposited on aluminum surface from WF6 with H2. W-CVD at high temperatures greatly reduced the amount of native aluminum oxide in the W/Al interface. A significant difference was not observed in the fluorine content at the interface for the samples prepared at different deposition temperatures (350, 450 degrees C). Therefore, aluminum fluoride seems to play a minor role in the deposition temperature dependence of contact resistance than aluminum oxide. However, in Al reduction W-CVD process, an AlF3 layer was observed as an insulating layer which causes high contact resistance