Influence Of Semiconductor Substrate On Characteristics Of Hafnium-Based Ferroelectric Capacitors

HfO2 has high dielectric constant,large band gap and good thermal stability.It is an ideal material to replace the silicon dioxide gate dielectric of traditional CMOS technology.In recent years,HfO2 has been widely used as High-K material in HKMG process below the 45 nm node,which solves the problem of gate leakage caused by carriers tunneling through the gate under the background of size reduction.The discovery of ferroelectric properties of doped HfO2 in 2011 quickly attracted widespread attention from academia and industry.HfO2-based ferroelectric materials have excellent ferroelectric properties at about 10 nm,and are compatible with advanced CMOS processes,breaking through the dilemma of traditional perovskite-type ferroelectric memories with limited integration density,and are new types of memories with great development potential.The paper deeply explores the influence of semiconductor substrates on the performance of hafnium-based ferroelectric capacitors.MFS ferroelectric capacitors are prepared using Si substrates and Ge substrates,and the polarization-electric field curves,saturation rates,and leakage currents of capacitors under different substrates are studied.Density,cycle performance and retention characteristics.Experimental results show that Ge-based devices have greater remnant polarization,faster device saturation rate,better cycle performance and longer retention characteristics,but the leakage current density is slightly larger.On this basis,the paper changed the crystal orientation of the substrate,the thickness of the ferroelectric layer,and the annealing crystallization temperature.The results showed that the ferroelectric properties and leakage current density of Gebased devices were positively correlated with the annealing temperature.Based on this phenomenon,this paper hypothesizes that the difference in ferroelectric properties of MFS capacitors on Si and Ge substrates is due to the thermal diffusion of Ge elements.The thesis further designed the interface layer isolation experiment and the undoped HfO2 experiment.The ferroelectric properties of the devices under the isolation of the interface layer are close,indicating that the substrate is the reason for the difference of the ferroelectric properties of the devices.Undoped HfO2 exhibits ferroelectricity,which provides strong evidence for the thermal diffusion of Ge.The XRD and TEM images show that the HZO film on the Ge substrate has a high proportion of orthorhombic phase,which is consistent with the electrical test results.Combined with the analysis of experimental and material characterization results,the hypothesis that the difference in ferroelectric properties of MFS capacitors on Si and Ge substrates is due to the thermal diffusion of Ge elements is convincing.In this paper,a detailed electrical test and mechanism analysis of the MFS structure capacitor is carried out,which provides a wealth of experimental data and research ideas for the subsequent study of the substrate influence of the hafnium-based ferroelectric memory.