Research On The Preparation Of Hafnium-Based Ferroelectric Gate Structure And The Effects Of Multiple Annealing On Its Electrical Properties

Properties including large remnant polarization,small thickness,low leakage current and high radiation resistance are neceesory for ferroelectric thin film applied in ferroelectric memory.Because of minimun thinkness limit,plannar ferroelectric capacitor route is adopted for current ferroelectric memory commercial product,which also prohibits its storage capacity development.Undoutedly,recently emerging HfO₂-based FeFET-type ferroelectric memory is a effective solution for this problom.Hence,this paper focuses on the research of the gate structure of HfO₂-based FeFET.The main research contents are as follows:?1?Metal/ferroelectric/insulator/semiconductor?MFIS?ferroelectric gate structure of TiN/Hf_0.5Zr_0.5O₂/HfO₂/Si was fabricated by atomic layer deposition?ALD?method.Scanning Electron Microscopy?SEM?and Energy Dispersive Spectroscopy?EDS?characterization results show that these ferroelectric gate have almost impeccable structure and clear interface.The electrical performance test of the prepared gate structure shows that the polarization characteristics were greatly affected by voltage,frequency and capacitor scale.Ferroelectric gate with an electrode radius of 100?m was selected as the experimental sample.Under testing conditions with voltage of 11 V and frequency of 1 kHz,the remnant polarization value 2P_r was 32.4?C/cm²,and the coercive electric field 2E_c 5.035 MV/cm.At the mean time,the hysteresis loop acquires good saturation state and rectangularity chacteristics.Small leakage current density,and excellent retention characteristic attained for these sample while the anti-fatigue characteristic was not so good.?2?The effects of heat treatment conditions and ambient temperature on the performance of ferroelectric gate were studied.It was found that the polarization,leakage current and anti-fatigue properties of ferroelectric gate were improved with the increase of annealing temperature at the annealing temperature range from 300°C to500°C.However,when the annealing temperature exceeded 500°C,the performance was reduced but the retention characteristics were less affected by temperature,indicating that the optimal annealing temperature is about 500°C.It was found that the performance of the prepared gate structure was affected by the environmental temperature and would gradually deteriorate when working at condition of environment temperature up to 75°C.?3?According to the characteristics of multiple high temperature process in the development process of ferroelectric transistor memory,the effect of multi-temperature annealing on the electrical performance of ferroelectric gate structure was studied in this paper.It was found that the polarization characteristics and leakage current characteristics were slightly reduced after three consecutive annealing treatments,and the retention characteristics remained in a good state,and the anti-fatigue properties was improved by three orders of magnitude from the first 10⁶ times.Under the condition of gate injection,the leakage current mechanism of samples after multi-temperature treatment are Ohmic Conduction mechanism at low electric field,Schottky Emission?S-E?mechanism at middle electric field,and Fowler-Nordheim?F-N?Tunneling mechanism at high electric field.The experimental results show that the hafnium oxide-based MFIS ferroelectric transistor gate structure has great temperature compatibility with the complementary metal oxide semiconductor?CMOS?process.