Formation of tungsten MOS gate structures using an integrated RTO/PVD process

Tungsten metal gate structures formed with air exposure between the process steps were compared to those formed using integrated sequences where the wafer was passed in vacuum (1E-7 torr) between steps. The wafers used were 150-mm, <100>, p-type silicon with bulk resistivity of 3-9 Ω-cm. All oxidations were done within 15 min of the HF dip used to remove the native oxide. Tungsten metal capacitors formed on thin silicon dioxide showed improvement in breakdown field and fixed oxide charge density when the samples were handled under vacuum between the oxidation and metal deposition steps. Annealing after metal deposition lowered the sheet resistance of the film as well as the fixed oxide charge density