Preparation And Physical Properties Of Silicon Substrate Metal Hafnium Thin Films Magnetron Sputtering And Physical Property Study

Transition group refractory metal hafnium（Hf）has important application value in the field of electronic devices,and one of its variantsα-Hf has a lattice constant that closely matches the third-generation semiconductor GaN,Si is currently the most mature in the semiconductor field,and it has the advantages of high quality and low cost.In the process of heteroepitaxy growth of GaN on Si substrates,α-Hf will play an important role as a lattice-matched buffer layer.α-Hf and GaN not only have the advantages of lattice matching,but also have good conductivity and light reflection characteristics,which is of great value for the research of GaN devices in optoelectronic applications.In this paper,α-Hf thin film materials were prepared on Si substrate by DC sputtering technology,and the influence of experimental parameters on film morphology,spatial structure,electrical properties and optical properties was studied.XRD（X-ray diffractometer）and SEM（scanning electron microscope）were used to characterize the microscopic morphology of thin film materials,such as phase,crystal structure and surface morphology,and the relationship between the preparation conditions and the micromorphology of thin films was analyzed.The effects of the preparation conditions on resistivity,I-V characteristics,light absorption and light reflection characteristics of thin films were studied by four-probe method,UV-visible-NIR spectrophotometer,I-V curve and spectral ellipsomemeter.The XRD results showed that the c-axis（002）of theα-Hf-50 W sample had a higher degree of preferential orientation,and the peak angle size and crystal plane spacing were closer to the data values of the standard powder phaseα-Hf.Different substrate temperatures had obvious effects on the crystallization quality of the film,and the samplesα-Hf-450℃ andα-Hf-550℃ both achieved（002）preferred orientation growth,among which the crystallinity of theα-Hf-550℃ sample was the best,the peak strength of the main diffraction peak（002）was the largest,the degree of preferred orientation was higher,and the peak angle and crystal plane spacing were closer to the data values of the standard powder phaseα-Hf.Theα-Hf-650℃ sample did not have obvious（002）diffraction peaks due to the high substrate temperature and poor crystallization quality.The SEM results showed that the surface of theα-Hf-50 W sample was denser and flatter,and the thickness of the film layer was smaller,which was due to the small sputtering power and slow deposition rate of sputtered particles,so the Hf atoms had enough time to move to a stable state,and the small thickness of the film layer was attributed to the low yield of sputtered particles.Different substrate temperatures had obvious effects on the morphology and growth mode of the film,α-Hf-450℃ was a combination of layered and island growth mode,α-Hf-550℃ was a two-dimensional layered growth mode,andα-Hf-650℃ was columnar growth,which was attributed to the energy provided by the substrate affecting the migration process of particles near the substrate.The electrical test results show that the resistivity of theα-Hf-550℃ film is6.957×10^-5Ω·cm,which is the smallest compared to other samples,because the higher crystallization quality reduces the barrier of free electron movement.The results of the I-V characteristic curve show that Schottky contact is formed betweenα-Hf and Si substrate,which has obvious rectification effect,and and its rectification ratio magnitude is in the range of 10³～10⁵.The optical test results show that the flatness and compactness of the surface of the film are related to light absorption and light reflectivity.α-Hf-100 W light reflectance was greater,which was attributed to the large diffuse reflection on its surface.α-Hf-550℃ film has greater light reflectivity due to its higher density and flatness.The light absorption ofα-Hf film was mainly related to the thickness of the film layer,and the larger the film thickness,the smaller the light absorption.Through the study of the microstructure and photoelectric properties ofα-Hf films,it is known that under certain conditions,α-Hf films achieve better（002）preferred orientation growth,soα-Hf films are powerful lattice-matched buffer layer candidates in the GaN growth process.