Study On The Characteristics Of Nd₂O₃-doped HfO₂ High-k Gate Dielectric Films Prepared By Atomic Layer Deposition

Since 2007,Intel introduced HfO2 high-k material into the 45nm Penryn core Xeon processor,HfO2 gate dielectric material has been widely studied and put into use.However,with the further development of the technical node(which has been developed below 16 nm),the transistor device size is gradually reduced;the thickness of the gate dielectric film is getting smaller and smaller.Hafnium base film oxygen vacancy defects and interface transition zone has more and more influence on device performance and reliability,the improve of the hafnium-based high-k material has become the focus of the current research.In this paper,the effects of Nd2O3 doping on the chemical structure and electrical properties of Hafnium-based high-k thin films were studied.The Hf-Nd-O films with different Nd2O3 doping ratios were prepared and annealed.The structure and characterization of Hf-Nd-O films were investigated to discusse the possibility of application of Hf-Nd-O thin films in the new technical nodes of semiconductor industry.The results are as follows:(1)Study on Optimization of Hf-Nd-O process parameters by ALD technology.The HfO2 thin films were prepared on the n-Si(100)substrate by different carrier gas(N2,Ar)and different oxygen sources(O3,H2O,O2-plamsa)using PE-ALD atomic layer deposition system.The Hf/O atomic ratio in the HfO2 film prepared by O3 as the oxygen source and Ar as carrier gas is closer to the ideal stoichiometric ratio,and the oxygen vacancy content in the film is the least through the XPS and PL analysis;Through electrical performance test,also found that the HfO2 film prepared by Ar as carrier gas and O3 as oxygen source has the minimum leakage current.The structure of pt/Hf-Nd-O/SiO2/Si/Ag MOS was prepared with Hf/Nd atomic ratio of 1:1 at different temperatures.It founds that the Hf-Nd-O film deposited at 340? has the highest capacitance and the minimum leakage current.(2)Study on The effect of Nd2O3 doping on the chemical structure and electrical properties of HfO2 thin films.Hf-Nd-O films with different Nd2O3 doping ratios were deposited on the n-Si(100)substrate by atomic layer deposition system.The results show that the composition of Hf-Nd-O films is more stoichiometric compared with pure HfO2 thin films,and the oxygen vacancy of the Hf-Nd-O thin film is reduced.The doping of Nd2O3 reduces the leakage current density and improves the film quality of the Hf-Nd-O film.The dielectric constant of the film was obtained by preparing Hf-Nd-O thin films with different thickness.It was found that when the doping content of Nd reached 30%,the dielectric constant of the film increased from 15.3 in HfO2 to 19.8(3)Study on the effect of Nd2O3 doping on the crystallization temperature and electrical properties of HfO2 thin films.The Hf-Nd-O films with Nd content of 30%were annealed in N2 atmosphere to study the electrical properties of pt/Hf-Nd/O/IL/Ag MOS structures with and without RTA annealing.The results show that the smaller leakage current density can be obtained when annealing at 700 ?.The leakage current density reaches to 2.7×10-6A/cm2@Vg=(Vfb+1)V,and when the annealing temperature is increased,the leakage current increases.The addition of Nd2O3 increases the crystallization temperature of HfO2 film to around 900?.It is found that the incorporation of Nd inhibits the formation of oxygen vacancy in the hafnium-based thin film,improves the dielectric constant of the film and reduces the leakage current density.The Hf-Nd-O as a gate dielectric material is expected to meet the requirements of the semiconductor industry new process node.