Research Of Negative Ferroelectric Field Effect Transitors

The subthreshold swing of ferroelectric negative-capacitor transistor can be lower than the theoretical limit of 60mV/dec,which is one of the key technologies to break through the transistor working voltage V_DDD and power consumption in the future.Since the concept of ferroelectronegative capacitor transistor was proposed in 2008,it has been widely concerned by scholars in the related researching region due to its simple device structure and excellent electrical performance.Compared with conventional transistors,negative-capacitor transistors have two advantages when applied to low-power circuits:?1?the swing of sub-threshold can be lower than 60mV/dec,the on-off current ratio does not decrease when the working voltage of the circuit is reduced,and in the same time the static leakage current does not increase;?2?smaller device size can reduce the circuit area.However,such transistors based on ferroelectric materials with negative capacitance characteristics are still faced with a series of problems such as the instability of negative capacitance,the influence of ferroelectric flip on their performance,and the lack of accurate models.Firstly,this paper studied and analyzed the physical mechanism and mathematical model of negative capacitance,simulated the transient response of ferroelectric negative capacitance by TCAD software,and studied the influence of ferroelectric material types and parameters on device performance.In addition,the hysteretic curve of the negative capacitance is measured by simulation,and the exact model parameters of the negative capacitance can be obtained by fitting the curve with experimental data.Secondly,the paper also designed a double gate negative capacitance transistor,and used Sentaurus to generate a three-dimensional structure of the device,and simulated its electrical performance.The simulation results confirmed that when the channel length of double-gate negative capacitance transistor is 40 nm,the cascade gate structure of ferroelectric capacitor and oxide layer capacitor has a good ability of gate controll.The saturation current and shut off current ratio is more than 10⁸,which is a very high switching current ratio,and the minimum SS of the device is 53 mv/dec.In addition,this article studied a negative capacitance transistor based on the 200nm SOI technology,Sentaurus structure and device simulation tools are used to get the electrical properties of the SOI negative capacitance transistor,the minimum sub-threshold swing SS of the SOI negative capacitance transistor can reach 30 mv/dec,and during the simulation,the channel surface voltage is recorded by the software,which confirmed the voltage amplification property of the negative capacitance.When the low sub-threshold swing is realized,the saturation current and turn-off current ratio of SOI negative capacitance transistor is greater than 10⁵,which means it has a good switching characteristic.