Reduction of molybdenum resistivity by a seed layer of Ti-W

A seed layer of TiW reduces the resistivity of sputter deposited molybdenum by up to 50%. With interposed TiW, molybdenum resistivity is constant at ca. 9 µΩ cm in the thickness range 25–800 nm while without the seed layer it is ca. 13 µΩ cm in the thickness range 300–800 nm, rising up to 18 µΩ cm for 25 mn thick film. TiW layer as thin as 2.5 nm is adequate for producing the effect. Molybdenum films both with and without the TiW nucleation layer have similar grain size and cubic structure with (110) as the strongest reflection. Strong crystallite clustering observed by AFM and FE-SEM is thought to be the reason for resistivity reduction. The TiW seed layer slows down the oxidation and wet etching rates of molybdenum, probably through surface area/porosity reduction.