Effects of phase of underlying W film on chemical vapor deposited-W film growth and applications to contact-plug and bit line processes for memory devices

This article presents the effects of phases of underlying nucleation layers prepared using two different reaction schemes, one is with B2 H6 and W F6 and the other with Si H4 and W F6, on the properties of chemical vapor deposited (CVD)-tungsten (W) thin film. From the x-ray diffractometry and transmission electron microscopy analysis, the B2 H6 -based nucleation layer was found to form as a poorly crystallized metastable Β -phase W while Si H4 -based one as a well-crystallized equilibrium α phase. The subsequently grown CVD-W film, as deposited with α phase, has significantly larger grains and, consequently, mitigated the increase of CVD-W resistivity due to size effect as well as lower resistivity on the B2 H6 -based nucleation layer than on Si H4 -based one. CVD-W film on the B2 H6 -based nucleation layer integrated on memory devices disclosed the improved electrical properties of interconnection such as lowered contact resistance at the metal line to bit line contact, lowered bit line resistance, and reduced parasitic capacitance. These improved electrical properties are explained with the enlarged grain size of CVD-W film on the B2 H6 -based nucleation layer compared to that on the Si H4 -based one, which is determined by the nucleation and growth behaviors on each nucleation layer.