Study On Preparation And Electrical Properties Of Al-doped Hafnium Oxide Thin Films

Hafnium oxide（Hf O₂）is a simple binary metal oxide with wide band gap,high dielectric constant,high refractive index,high transmission,high resistance to laser damage and high melting point.It has a wide application in the field of optical and electronic devices.Since Intel first used Hf O₂as a high dielectric gate material in2007,Hf O₂has been regarded as a standard grid dielectric material in industry and widely used in advanced metal-oxide-semiconductor field effect transistors.Hf O₂is extensively applied in logic devices and non-volatile memory due to its excellent ferroelectric and resistive properties and good compatibility with CMOS processes.Hf O₂has a variety of crystal structures and is very conducive to control its performance.In addition,element doping（such as Si,Al,Gd or Y）can also be used to tune the phase structure and thereby change its performance.Among them,Aluminium-doped Hf O₂,as an excellent high dielectric material,has the advantages of low leakage current density,good stability,and good compatibility with CMOS process,exhibiting good potential application in next generation integrated circuits and non-volatile memory devices.Herein,homogeneous and dense doped Hf O₂thin films were prepared by atomic layer deposition（ALD）,and their microstructures and electrical properties were studied.The main research contents and results are as follows:（1）Aluminum-doped Hf O₂thin films with high quality can be controllable prepared by ALD.The structure,composition and morphology of the Hf O₂thin films were characterized.The influence of doping concentration and doping method on the performance of the films was studied.The results show that the grain size of the annealed film increases with the increase of doping concentration.The doped film prepared by ALD has good surface morphology,and the increase of doping concentration increases the roughness of the film,which is related to the phase transition of the film caused by doping.In addition,the film roughness annealed in O₂is better than that annealed in N₂atmosphere.With the increase of doping concentration,the amorphous oxygen defects in the film increase,and the characteristic peaks of the elements shift to the direction of high binding energy.（2）Through I-t,Tafel,MC-V,Mott-Schottky tests on high quality thin film devices prepared by different processes,and the electrical performance of the devices is studied.The results show that as the thickness of the film increases,the leakage current decreases,the capacitance strength in the depletion zone decreases,and the charge capture ability decreases.The device with sandwich structure has higher leakage current when doped with high Al content,indicating Hf O₂film has smaller leakage current than Al₂O₃film.Besides,32A+64H+32A sandwich process devices have larger hysteresis windows and better stability.For multilayer stacked structures,4（16A+16H）process devices have better charge capture performance and larger hysteresis window.The results show that the 32A+64H+32A sandwich device has good electrical performance,storage performance and stability.Increasing oxygen vacancy concentration is responsible for better charge capture performance and larger storage window.