Deposition of tungsten by plasma enhanced chemical vapour deposition

The standard method of depositing tungsten is by LPCVD using SiH4-H-2-WF6 c hemistry at temperatures of >300 degrees C. This work has studied the use o f PECVD with H-2-WF6 for tungsten deposition. It was found that at depositi on temperatures below 200 degrees C, the layers are polycrystalline beta ph ase tungsten, resistivity 50 mu Omega cm. Annealing at 900 degrees C decrea ses the resistivity to 10 mu Omega cm. The tungsten layers deposited at 200 degrees C and above are of the alpha phase and exhibit an as deposited res istivity of 15 mu Omega cm for 150nm layers. For the layers deposited on ti tanium at T>300 degrees C the initial deposition is dominated by the reduct ion of WF6 by the titanium until a self limiting thickness is produced. Thi s results in titanium fluoride species being incorporated at the titanium-t ungsten interface.