Preparation Of High-? Dielectric Strontium Oxide Film And Its Application In Thin Film Transistors

With the continuous advancement and development of information society,21th century has become panel display era,however,most of flat-panel display devices are active matrix liquid crystal display?AMLCD?devices.The key component is TFT that plays an important role in AMLCD.The conventional amorphous-Si TFTs exhibited low mobility and strong photo-sensitive,and polycrystalline-Si TFTs exhibited complicated fabrication technology,these factors limited the application in boarder areas.The metal oxide semiconductors are introduced into TFTs that can increase mobility sharply and reduce cost effectively,so that they are fabricated and applied in large area.However,we can hardly reduce the operating voltage in SiO₂-based TFTs due to its small dielectric constant.To solve this problem,we need to explore new high-k dielectrics to replace SiO₂ dielectric so that can fabricate high performance and low operating voltage TFTs.In this thesis,the history,operating principle,application and fabrication of TFTs were introduced firstly.In the first section,the high-k dielectric SrO_x thin films were fabricated using simple and low-cost sol-gel process.The formation and properties of SrO_x thin films with various annealing temperatures?400,500,600 and 700 ^oC?were investigated systematically.The electrical analysis indicated the insulating property of SrO_x thin film were improved with increasing annealing temperatures.The SrO_x thin films annealed at temperature high than 400 ^oC exhibits low leakage current density(¹0^-8 A cm^-2)and large capacitance density(>350 nF cm^-2).To further explore the potential applications of the SrO_x thin film for thin-film transistors,the SrO_x thin films were integrated into In₂O₃ TFTs.The optimized In₂O₃/SrO_x TFT shows a high average field effect mobility of 5.61 cm² V^-1 s^-1,a small SS value of 110 mV dec^-1 and large on/off ratio of 10⁷.Finally,to demonstrate the potential of In₂O₃/Sr O_x TFT toward more complex logic application,the resistor-loaded inverter was constructed and exhibited a gain of 9.7.In the second section,the passivation layer Al₂O₃ thin films with various concentrations of precursor solutions were investigated,and also integrated into In₂O₃/ZrO₂ TFTs for testing.The transfer characteristics indicated the Al₂O₃ thin films can modulate the performance and also improved operating stability.The optimized Al₂O₃/In₂O₃/ZrO₂ TFT shows a high average field effect mobility of 21.22 cm² V^-1 s^-1,a small SS value of 100 mV dec^-1,a large on/off ratio of 10⁷ and a negligible hysteresis voltage.Dynamic measurements demonstrated the Al₂O₃/In₂O₃/ZrO₂ TFTs have stronger operating stability clearly.Finally,Al₂O₃-0.04/In₂O₃ TFT was introduced into low-voltage resistor-loaded inverter and exhibited a gain of 9.8.All the device parameters were obtained at 3 V,which represent a step toward portable and low-consumption electronics and circuits.