J. Phys. IV France 09 (1999) Pr8-827-Pr8-833
Deposition of tungsten by plasma enhanced chemical vapour depositionM.F. Bain, B.M. Armstrong and H.S. Gamble
Northem Ireland Semiconductor Research Centre, Department of Electrical and Electronic Engineering, The Queen's University of Belfast, Belfast BT7 1NN, Ireland
The standard method of depositing tungsten is by LPCVD using SiH4-H2-WF6 chemistry at temperatures of >300°C. This work has studied the use of PECVD with H2-WF6 for tungsten deposition. It was found that at deposition temperatures below 200°C, the layers are polycrystalline beta phase tungsten, resistivity 50µΩcm. Annealing at 900°C decreases the resistivity to 10µΩcm. The tungsten layers deposited at 200°C and above are of the alpha phase and exhibit an as deposited resistivity of 15µΩcm for 150nm layers. For the layers deposited on titanium at T>300°C the initial deposition is dominated by the reduction of WF6 by the titanium until a self limiting thickness is produced. This results in titanium fluoride species being incorporated at the titanium-tungsten interface.
© EDP Sciences 1999