Preparation And Dielectric Properties Of Aluminlum Oxide Thin Films Grown By Atomic Layer Deposition

As the size of field effect transistor shrinking down to nanoscale,the high dielectric film materials with excellent performance are urgently needed to replace the traditional Si O2 gate dielectric layer,which resulting in lager tunneling current due to its thickness restriction.In this thesis,Al₂O₃ thin film on silicon wafer was fabricated via atomic layer deposition technology.To further promote the dialectical property,nanostacked structure was also prepared.The research can provi de theoretical basis and technical support for high dielectric film material to improve dielectrical property and application in electronics field.Al₂O₃ film was synthesized utilizing atomic layer deposition technique.The influence of deposition process,film thickness and annealing treatment on dielectrical property was investigated.The structure and electrical properties were studied by XRD,XPS,LCR Meter and AFM method.As a result,Al₂O₃ film showed optimum performance at 225 ℃ when impulse time of TMA is 0.3 s and the number of deposition circles is 300 cycle.Annealing temperature exerts a tremendous influence on Al₂O₃ dielectric film.When annealing temperature was 500 ℃,dielectric constant is 8.15 and minimum drain current is obtained.The leakage current is 6.12×10-8 A/cm2 when voltage is 3 V.Al₂O₃/Hf O2/Al₂O₃ gate with nano-stacked structure was fabricated so as to improve thedielectrical property of Al₂O₃ film.The effect of surface morphology,composition and ratio of cycle time was studied.As a result,the Al₂O₃/Hf O2/Al₂O₃ film showed excellent properties.The optimal ratio of Al₂O₃/Hf O2/Al₂O₃ gate is 1:2:1 and the dielectric constant rises from 8.15 to 10.28,which can restrain leakage current effectively.The leakage current decreases from 6.12×10-8 A/cm2 to 2.37×10-8 A/cm2 when the voltage is 3 V.Al₂O₃/Hf O2/Al₂O₃ film was applied to transistor while ZnO film was used as active layer.As a result,the stacked structure showed excellent regulatory effect.The on/off ratio is 106 and the off-current is 10-11 A.The device showed lower power consumption which can make it work stably.