Tuning The Ferroelectric Properties Of Hf_0.5Zr_0.5O₂ Thin Films On Ge Substrates

Hafnium oxide-based ferroelectric materials have the characteristics of compatibility with CMOS process,strong miniaturization ability and wide bandgap,which play an important role in promoting the development of ferroelectric memory.In addition,germanium has a relatively high carrier mobility and can be used as a channel material for ferroelectric field effect transistor?FeFET?.The integration of germanium and hafnium oxide-based ferroelectric thin films is expected to improve the performance of ferroelectric memory.However,the effect of their interface on hafnium oxide-based ferroelectric thin films has rarely been reported.Therefore,Hf_0.5Zr_0.5O₂?HZO?thin films were prepared on germanium substrate by pulsed laser deposition and their electrical properties were studied in this thesis.The detailed research contents are as follows:1.By changing the parameters of substrate temperature,oxygen pressure and annealing temperature,the effects of these parameters on the properties of HZO films in Pt/HZO/Ge capacitor structure were systematically studied.With the increase of substrate temperature,oxygen pressure and annealing temperature,the polarization of HZO films showed an increasing trend and a decreasing trend subsequently.The film obtained at an oxygen pressure of 30 mTorr,a substrate temperature of 300°C and an annealing temperature of 500°C has relatively excellent ferroelectric performance.The remnant polarization 2P_r can reach 16.3?C/cm².At the same time,its endurance test results indicate that the remnant polarization of the film decreased by 47%after 10⁵ switching cycles.In general,the test results show that HZO thin films have obvious ferroelectric properties.2.By changing the parameters of oxygen pressure and annealing temperature,the effects of these parameters on the properties of HZO films in Pt/HZO/ZrO₂/Ge capacitor structure were systematically studied.The films prepared at an oxygen pressure of50 mTorr show excellent ferroelectric performance.With the increase of annealing temperature,the polarization showed an increasing trend and a decreasing trend subsequently.The films annealed at 500°C have excellent performance,and the remnant polarization 2P_r was 9.3?C/cm².Moreover,the films prepared at an oxygen pressure of50 mTorr and an annealing temperature of 500°C show excellent endurance performance.The remnant polarization decreases by 48%after 10⁶ switching cycles.PFM test results show that with the increase of oxygen pressure and annealing temperature,the ferroelectric properties is improved at first,while it is weakened subsequently.3.By changing the parameters of oxygen pressure and annealing temperature,the effects of these parameters on the properties of HZO films in Pt/HZO/ZrO2/HZO/ZrO₂/Ge capacitor structure were systematically studied.With the increase of oxygen pressure and annealing temperature,the polarization of the films showed an increasing trend and a decreasing trend subsequently.The film obtained at an oxygen pressure of50 mTorr has excellent performance.After annealing at 500°C,the remnant polarization2P_r is 13.0?C/cm².Moreover,the film has relatively excellent endurance performance.The remnant polarization decreases by 59%after 10⁷ bipolar switching cycles.Subsequently,the films prepared under different conditions were characterized by PFM.With the increase of oxygen pressure and annealing temperature,the ferroelectric properties is improved at first,while it is weakened subsequently.It has good ferroelectric properties at an oxygen pressure of 50 mTorr and annealing treatment conditions of500°C.4.HZO thin films in Pt/ZrO₂/HZO/ZrO₂/Ge capacitor structure were studied.The results show that the polarization properties of the films is improved as the annealing temperature increases.At the annealing temperature of 600°C,the remnant polarization2Pr is 15.4?C/cm².Endurance test results show that the remnant polarization drops by 10%after 10⁵ switching cycles.Moreover,the PFM hysteresis loop has a good squareness,and the phase changes 157°.The PFM amplitude curve has an obvious butterfly curve characteristics.