Optical Properties And Structyres Of Transparent Oxide Semiconductor Hfo₂

The transparent oxide semiconductor HfO2,which has high transmittance in the visible region and high reflectivity in the infrared region,belongs to the third generation Wide Band-gap Semiconductors.It has been widely used in many fields such as microelectronics and optoelectronics.As the rapid shrinkage of integrated circuit(IC)transistors,the direct tunnel leakage current and dissipation rate of the traditional silicon dioxide(SiO2)gate dielectric increase rapidly.The development of the IC transistors is hardly to be satisfied with SiO2 in the future.We need to find out some new materials with high dielectric(K)to replace SiO2 as soon as possible.Among all the high-k materials,Hf02 is one of the best candidates for new gate dielectric materials,because it has high dielectric constant,wide band gap,high breakdown electric field,and good thermal stability on Si substratesIn this paper,a series of nano-scale HfO2 thin film samples were grown by atomic vapor deposition with the different of Si substrate temperatures and oxygen flow rates.Multiple analytical techniques,including X-ray photoelectron spectroscopy(XPS),grazing incidence X-ray diffraction(GIXRD),multi-angle ellipsometry(VASE),and Rutherford backscattering spectroscopy(RBS),were applied to characterize these films and penetrative analyses were performed.The composition ratio of the elements at surface of the HfO2 thin films were obtained from XPS.The chemical shift mechanism of the Hf 4f peaks was well explained by the change of intensity ratio between Hf4+ 4f and Hfx+ 4f peaks in photoelectron spectroscopy;the thickness,optical constant and optical band gap of the HfO2 thin films were determined accurately by VASE;through the simulation of RBS experimental data,the thickness and elemental composition ratio of HfO2 films were obtained;via GIXRD,it was found that all of the monoclinic,orthorhombic,and tetragonal phase were existed in the HfO2 thin films.As the increased thickness of the HfO2 thin film,the orthorhombic and tetragonal phases gradually disappear,and the crystallite size becomes smaller.In summary,The HfO2 film deposited on Si substrates at higher deposition temperature and oxygen flow rate is polycrystalline with higher quality;and as the film thickness increases,the crystal phase tends to be single.