Effect Of Nickel Silicide Electrode On Electrical Properties Of Hf_0.5Zr_0.5O₂ Ferroelectric Thin Films

Ferroelectric memory is currently regarded as one of the most promising emerging memories with clear advantages such as non-volatility,high reading/writing speed,low power consumption and good radiation hardness.HfO₂-based ferroelectric materials offer many advantages in terms of scalability and complementary metal-oxide-semiconductor（CMOS）compatibility,which are promising candidates for various applications,including ferroelectric capacitor type,ferroelectric field-effect transistor（Fe FET）type and ferroelectric tunnel junction type memories.Metal nickel silicide has excellent properties such as good oxidation resistance and small resistivity,and its crystal structure and lattice parameters match well with those of HfO₂-based ferroelectric thin films.In this dissertation,metal-ferroelectric-metal（MFM）and metal-ferroelectric-semiconductor（MFS）capacitors are prepared for capacitor type and Fe FET type ferroelectric memory applications.The capacitors are fabricated with Hf_0.5Zr_0.5O₂（HZO）thin films and nickel silicide electrodes.After determination of the optimal annealing temperature,the capacitor structure is optimized.Moreover,mitigation of wake-up effect and improvement of endurance for the ferroelectric HZO thin films are realized by studing the effect of nickel silicide electrode on electrical properties of HZO thin films.The main research contents and results are summarized as follows:（1）The effects of the crystallinity of the NiSi₂ bottom electrode and the annealing temperature of the capacitors on the electrical properties of HZO ferroelectric thin films are studied based on MFM capacitors.It is found that the electrical properties of the HZO ferroelectric films are effectively improved by the NiSi₂ bottom electrodes with a high crystallinity.Thus,using NiSi₂ bottom electrodes with a high crystallinity,the HZO MFM capacitors annealed at 450^oC exhibit excellent ferroelectric properties.Moreover,the wake-up effect of the HZO film can be effectively weakened by the NiSi₂ electrodes.It is also found that the endurance of the HZO thin film is significantly improved by the NiSi₂ gate electrodes based on the study of the MFS capacitors,but the ferroelectric performance of MFS capacitors is not improved by the NiSi₂ gate electrodes.（2）The effects of the crystallinity of the NiSi bottom electrode and the annealing temperature of the capacitors on the electrical properties of HZO ferroelectric thin films are studied based on MFM capacitors.It is found that the electrical properties of the HZO ferroelectric thin films are not obviouly affected by the crystallinity of the NiSi bottom electrodes.The HZO MFM capacitors annealed at 450^oC exhibited large polarization and almost no wake-up effect.The results indicate that NiSi is more suitable to be used as the gate electrodes of MFS capacitors.It can not only significantly improve the endurance of the MFS capacitors,but also enhance the remant polarization.