Preparation,Optical And Electrical Properties Of Titanium Nitride Thin Films

Titanium nitride(TiN_x) is a transition metal nitride which has a structure combined with covalent bond,ionic bond and metal bond.Because of its interesting physical and chemical properties,such as high hardness,high melting point,high chemical stability,good electrical conductivity and high optical reflectivity in the infrared band,in recent decade,TiN_x thin films were widely studied and used in cutting tools,decoration and in the field of anti-friction.Though the high hardness,high melting point and high chemical stability of TiN_x thin films has been extensively investigated,the electrical and optical properties of TiN_x thin films remain to be further studied.In this work,TiN_x thin films were prepared by DC magnetron reactive sputtering on p-type Si(111) substrates.The influence of chamber pressure,substrate temperature,flow ratio of Ar/N₂ and sputtering current on the structure and properties of TiN_x thin films were investigated.The crystallinity and crystal orientation of the TiN thin films were investigated by X-ray diffraction diffractometer(XRD).The surface morphologies were characterized by AJ-3 atomic force microscope(AFM) operation in tapping mode.The sheet resistance was conducted by SDY-5 four-point probe.The thickness of the thin films is measured by DEKTAK 6M step profilometer. The optical properties of the thin films were analyzed by measuring the reflectivity using a SHIMADZU UV-3101PC spectrophotometer.The main contents and results of the work include:1.The influence of chamber pressure on the structure and properties of TiN_x thin filmsFor investigating the influence of chamber pressure on the structure and properties of TiN_x thin films,samples were prepared under different chamber pressure(other technological parameters were fixed).It is shown that the main component of the TiN_x thin films is cubic TiN with(200) prefered orientation.As the chamber pressure increase,the lattice constants and resistivity of the TiN_x thin films increase,whereas the thickness and average reflectivity in near-infrared band decrease.What is more, the mean grain size analyzed by AFM off-line software closed to that calculated by Scherer's formula in XRD experiment within a maximum relative error 10%.2.The influence of substrate temperature on the structure and properties of TiN_x thin filmsFor investigating the influence of substrate temperature on the structure and properties of TiN_x thin films,samples were prepared under different substrate temperature(other technological parameters were fixed).It is shown that the main component of the thin films is cubic TiN with(111) preferred orientation when the substrate temperature is below 240℃,there is a transition of the preferred orientation from(111) to(200) when the substrate temperature increase,when the substrate temperature increase,The resistivity of TiN_x thin films increase gradually,while the average reflectivity in near-infrared band exist a maximal value at 330℃.3.The influence of the flow ratio of Ar/N₂ on the structure and properties of TiN_x thin filmsFor investigating the influence of the flow ratio of Ar/N₂ on the structure and properties of TiN_x thin films,samples were prepared under different flow ratio of Ar/N₂(other technological parameters were fixed).It is shown that the main component of the TiN_x thin films is cubic TiN with(200) prefered orientation.The intensity of(200)-peak increases as the flow ratio of Ar/N₂ increases.When the flow ratio of Ar/N₂ increases,the thickness decrease and the resistivity of TiN_x thin films has a minimal value,while the the average reflectivity in near-infrared band exists a maximal value.4.The influence of sputtering current on the structure and properties of TiN_x thin filmsFor investigating the influence of sputtering current on the structure and properties of TiN_x thin films,samples were prepared under different sputtering current(other technological parameters were fixed).It is shown that the main component of the TiN_x thin films is cubic phase TiN.With the increase of sputtering current,there is a transition of the preferred orientation from(111) to(200),the thickness and rms roughness of the TiN_x thin films increase,the resistivity of TiN_x thin films has a minimal value,while the average reflectivity in near-infrared band exists a maximal value.The structure and properties of the TiN_x thin films depend obviously on the technological parameters,such as chamber pressure,substrate temperature,the flow ratio of Ar/N₂ gas and sputtering current.The TiN_x thin films with best optical and electrical properties,that is,lowest resistivity(33.7μΩ·cm) and highest average reflectivity in near-infrared band(85%),were deposited by optimized technological parameters(chamber pressure 0.3 Pa,substrate temperature 330℃,the flow ratio of Ar/N₂ gas 15:1,sputtering current 0.35A and deposition time 3h).