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

Tungsten (W) films were deposited on Si(100) from tungsten hexacarbonyl, TW (CO),I, by low-pressure chemical vapor deposition (CVD) in an ultra-high va cuum (UHV)-compatible reactor. The chemical purity, resistivity, crystallog raphic phase, and morphology of the deposited films depend markedly on the substrate temperature. Films deposited at 375 degrees C contain approximate ly 80 at.% tungsten, 15 at.% carbon and 5 at.% oxygen. These films are poly crystalline P-W with a strong (211) orientation and resistivities of >1000 mu Omega cm. Vacuum annealing at 900 degrees C converts the metastable beta -W to polycrystalline OL-W, With a resistivity of approximately 19 mu Omega cm. The resultant alpha-W films are porous, with small randomly oriented g rains and nanoscale ((100 nm) voids. Films deposited at 540 degrees C are h ighpurity (>95 at.%) polycrystalline a-W, with low resistivities (18-23 mu Omega cm) and a tendency towards a (100) orientation. Vacuum annealing at 9 00 degrees C reduces the resistivity to approximately 10 mu Omega cm, and r esults in a columnar morphology with a very strong (100) orientation. (C) 2 000 Elsevier Science S.A. All rights reserved.