Studies On The Characteristics Of RRAM Device Based On Hafnium Oxide

With the development of the semiconductor industry in the information age,the demand for various electronic products,especially information storage products,has shown a rapid upward trend.At present,flash is the most mainstream memory on the market.It is based on a floating gate structure.However,due to the miniaturization trend of the entire semiconductor industry,the physical size of flash has approached its theoretical limit and cannot continue to adapt to the future.People have begun to study some new non-volatile memory devices.Among them,the resistive memory has attracted people's attention due to its simple structure,fast read and write speed,high endurance,long data retention time,and multi-value storage capability,which is one of the research hotspots in recent years.There are many intermediate dielectric layer materials that can generate resistive switching phenomena.Among all of them,the preparation technology of HfO₂ is mature and compatible with the COMS technology.In addition,the RRAM device based on the HfO₂has good stability and can be doped,so that we can regulate its resistive switching performance.The RRAM devices based on HfO₂ are prepared and studied in this dissertation.The main contents and achievements are as follows:1.In this paper,Ti/HfO₂/Pt RRAM devices are prepared.And their characteristics investigated from DC switching,resistive switching mechanism,and conductive mechanism.The study found that the prepared Ti/HfO₂/Pt RRAM devices have good retention ability(>10⁴s),better cycling endurance(>10²),and suitable ON/OFF ratio(?10²).The resistive switching of the devices is caused by the formation and dissolution of the conductive filaments(CFs),which is composed of oxygen vacancies.The conduction mechanism of Ti/HfO₂/Pt RRAM device in low resistance state is ohmic conduction mechanism,and the conduction mechanism in high resistance state is SCLC mechanism.2.Ti/Al₂O₃:HfO₂/Pt RRAM devices are prepared,which doped Al in the HfO₂ film.The purpose is to improve the problem of scattered performance parameters and poor uniformity.After doping treatment,the resistive switching characteristics of the deices were improved,such as lower forming voltage,SET/RESET voltage and better electrical uniformity.Because the doping of Al increases the concentration of oxygen vacancies,so that the operating voltage of the device is reduced.In addition,the randomness of conductive filaments were reduced after Al doping,so that the uniformity of the electrical performance of the device were improved.Doping has little effect on the conductive mechanism of the devices.The conduction mechanism of Ti/Al₂O₃:HfO₂/Pt RRAM devices are consistent with that of Ti/HfO₂/Pt RRAM devices.3.The multilevel memory characteristics of Ti/Al₂O₃:HfO₂/Pt RRAM devices were studied.Different low resistance values were obtained by controlling the compliance current during the SET process.The compliance current during the SET process has a greater impact on the low-resistance resistance value and the RESET current(linear relationship in double logarithmic coordinates),but has a small impact on the SET/RESET voltage.By controlling the stop voltage during the RESET process,different high resistance values were obtained.In logarithmic coordinates,the high-resistance resistance value increases with the increase of the stop voltage during the RESET process,the SET voltage value increases slowly with the increase of the stop voltage.The RESET voltage value and RESET current value did not show a significant change trend with the increase of the stop voltage.