Investigation On Microstructure And Mechanical Properties Of W(N) Thin Films

The W?N?film has excellent physical properties such as high hardness,high melting point,high electrical conductivity,and stable chemical properties.These characteristics make it has a very wide range of application prospects,and can be specifically applied to the resistance diffusion barrier of microelectronic devices,the gate electrode of a metal oxide semiconductor field effect transistor,and a hard wear-resistant protective coating of a cutting tool.In addition,many studies have shown that the application performance of W?N?thin films is determined by the phase structure and component composition,that is,they have a very close relationship with the parameters of the preparation process,but because the relationship between them is more complex,Therefore,we must systematically study the relationship between them in order to obtain the optimal film structure.So far,there are many methods for preparing W?N?thin films,such as pulsed laser deposition,ion beam sputtering deposition,reactive magnetron sputtering,atomiclayerdeposition,organometallicchemicalvapordeposition,and plasma-enhanced chemical vapor deposition.Among these methods,reactive sputtering is of particular interest because of its features of being able to synthesize thin films with high quality and large area under low deposition temperature conditions.The microstructure and mechanical properties of the reactive sputter deposited W?N?thin film are affected by experimental parameters such as nitrogen flow rate?FN₂?,substrate bias?V_b?,and temperature?T?.Since WN_x has a lower formation heat than TiN,NbN,and ZrN,WN_x should be more difficult to synthesize than TiN,NbN,and ZrN.Therefore,in order to clarify the relationship between the hardness of the film and the structure,we need to carry out systematic experimental research.In this thesis,we prepared W?N?thin films by RF magnetron sputtering.The influences of deposition parameters such as nitrogen flow,substrate bias,and deposition temperature on phase microstructures,surface morphology,deposition rate,and hardness are investigated.There have been a lot of reports on small-atom doped in transition metal to improve the mechanical properties of transition metal.Supersaturated solid solutions were observed in these transition metals.Small atom doping has a great improvement in its mechanical properties.However,investigations of nitrogen atom doping have not been reported yet.In this thesis,nitrogen doping W?N?films were prepared using a radio frequency magnetron sputtering through changing gas flow rate.The results show that nitrogen-doped tungsten supersaturated solid solutions were formed.