Fabrication And Devices Performance Investigation Of Hf-based High-k Gate Dielectric Thin Films By Sol-gel

With the development of very large scale integrated circuit and MOSFET device feature size shrinking,the traditional gate dielectric SiO₂ film has reached its physical limits because it has a low dielectric constan??3.9?.Because of quantum tunneling effect,the leakage current of gate dielectric layer has increased dramatically.It led to a sharp decline in reliability and stability of the device and affect the service life of the device seriously.In recent years,the Hf high dielectric material became the ideal alternatives to traditional SiO₂ gate dielectric material because of its higher values of k,good thermal stability and excellent interface with Si substrate,larger band gap and larger valence band and conduction band offset.It has attracted more and more attention and research.As the core of the flat panel display,thin film transistor?TFT?devices plays a decisive role to improve the performance of flat panel display.The gate insulation layer of the TFT device directly affects the performance of the device.The Hf-based high dielectric constant material can effectively reduce the leakage current of the device and reduce the threshold voltage with high dielectric constant instead of the traditional SiO₂ gate dielectric.And it can improve the regulation of the current between the source and the drain.At present,there are many methods for the preparation of Hf-based high dielectric film materials.Atomic layer deposition?ALD?is the mainstream technology for the fabrication of gate dielectrics in the industry.However,ALD technology requires a high vacuum environment and a very slow film growth rate,which is not conducive to large-scale modernization produce.The preparation of Hf-based high dielectric film material by sol-gel method is low,the operation is simple and the material composition is easy to control.Therefore,the use of sol-gel method for the preparation of Hf-based high-k gate dielectric films and devices is of great importance for the development of integrated circuits.Because the film is prepared using a solution,the sol-gel method must be heat treated for curing,and the temperature of the heat treatment has a direct effect on the quality of the film.Based on the previous reports,it can be seen that the hafnium-based gate dielectrics prepared by most methods hinder their continued application in MOSFETs and TFTs due to low crystallization temperature,not too high dielectric constant,and deteriorated interface characteristics at high temperatures.Based on these thorny problems,this paper adopts Ti,Al and other elements to effectively improve the properties of HfO₂ film,regulating the performance of MOS and TFT devices.1.The HfO₂ films were prepared by sol-gel method.The effects of different annealing temperatures on the structure,optical and electrical properties were investigated.The experimental results show that the HfO₂ thin films have different crystal structures at different annealing temperatures,and the annealing temperature effectively regulates the optical band gap of the HfO₂ films.The electrical test shows that the 400? annealed samples show the optimized electrical properties.2.Ti-doped HfO₂ gate dielectric thin films were prepared by sol-gel method.The effects of different baking temperatures on the structure,optical and electrical properties of the films were investigated.When the baking temperature is 200?,the electrical properties of the films are the best,and their dielectric constant increases obviously with respect to HfO₂ films.3.Al-doped HfO₂ gate dielectric films were prepared by sol-gel method.The effects of different annealing temperatures on the optical and electrical properties of the films were investigated.Electrical tests show that samples annealed at 400?show optimized electrical performance and are significantly inhibited by leakage current.4.The InZnO/HfAlOx thin film transistor was fabricated by sol-gel method.The effect of the insulating layer on the performance of the thin film transistor was studied by changing the annealing temperature of HfAlOx film and the thickness of the insulating layer.The results show that the InZnO/HfAlOx thin film transistor exhibits better performance when the HfAlOx film is annealed at 600?.