Tungsten chemical vapor deposition using tungsten hexacarbonyl: microstructure of as-deposited and annealed films

Abstract Tungsten (W) films were deposited on Si(100) from tungsten hexacarbonyl, [W(CO)6], by low-pressure chemical vapor deposition (CVD) in an ultra-high vacuum (UHV)-compatible reactor. The chemical purity, resistivity, crystallographic phase, and morphology of the deposited films depend markedly on the substrate temperature. Films deposited at 375°C contain approximately 80 at.% tungsten, 15 at.% carbon and 5 at.% oxygen. These films are polycrystalline β-W with a strong (211) orientation and resistivities of >1000 μΩ cm. Vacuum annealing at 900°C converts the metastable β-W to polycrystalline α-W, with a resistivity of approximately 19 μΩ cm. The resultant α-W films are porous, with small randomly oriented grains and nanoscale ( 95 at.%) polycrystalline α-W, with low resistivities (18–23 μΩ cm) and a tendency towards a (100) orientation. Vacuum annealing at 900°C reduces the resistivity to approximately 10 μΩ cm, and results in a columnar morphology with a very strong (100) orientation.