Study On The Total Ionizing Dose Effect Of Nano-MOS Devices

The continuous development of aviation,nuclear industry and other businesses has led to higher requirements for the precision and integration of their internal electronic instruments.Smaller feature size transistors bring higher computing power,lower power consumption and even cost reduction to chips.The use of nanoscale devices to form devices used in the aviation and nuclear industries is essential,so the study of the degradation mechanism of devices under nuclear radiation or cosmic rays and other cumulative bombardment with high-energy particles,to provide theoretical support for radiation reinforcement and enhance chip reliability has become a research focus.This paper focuses on these key points and proposes and verifies the degradation mechanism of nanoscale MOS devices using a combination of simulation and experiment.This article first uses TCAD Silvaco software to establish a MOS device model,and adjust the parameters to make the model match the electrical characteristics of the actual device.The total dose simulation model is added to obtain the device data after the device is affected by the oxide layer and the trapped charge at the interface,and the electrical parameters are extracted and the degree of degradation is verified.The transfer characteristic curve and potential distribution of the device under different irradiation doses are analyzed,and it is shown that the larger the total irradiation dose,the higher the degradation degree of the device,and the NMOS device has a "rebound" effect due to the opposite electrical properties of the two trapped charges.Finally,the influence of the structural parameters of the device on the total dose effect is discussed.The shorter the channel of the NMOS device,the easier it is to turn on the parasitic transistor,which leads to an increase in the off-state leakage current and the deterioration of the device.The less than the total channel length,the worse the device degradation.In general,the main factor for the degradation of nanoscale devices by the total dose effect is the effect of the trapped charges in the shallow trench isolation region.Then,the analysis focuses on the total dose effect experiments for device size 500 nm/30 nm PMOS devices.The experiments show that γ-radiation degrades the device with negative threshold voltage drift,increased subthreshold swing variation,and increased maximum trans-conductance variation.PMOS oxide layer and interface trap positive charge,shallow slot isolation trap charge Coulomb effect reduces the effective gate length of the device and high K dielectric introduces new trap charge together to make the device threshold voltage negative drift.By modifying the previous simulation model by adding only the shallow slot isolation trap charge and comparing it with actual use,it is verified that the main factor of degradation is the shallow slot isolation oxide trap charge.The increase in subthreshold swing indicates that the device off-state leakage becomes larger with enhanced irradiation,and the cross-conductance reflects the change in carrier mobility,thus irradiation reduces the device mobility,both of which impair the device amplification capability.Finally,it is verified that 1/f noise has a direct correlation with the device electrical parameters,which can reflect the internal trap characteristics of the device.Finally,the influence of the total dose effect on MOS devices under multi-variable conditions is discussed.Changing the structural parameters of the device shows that the shorter the channel,the more serious the degradation of NMOS and PMOS devices.Changing the gate voltage shows that the greater the gate voltage of the NMOS device,the higher the degree of degradation,while the smaller the gate voltage will improve the off-state leakage to a certain extent due to the "bounce" effect.After changing the experimental parameters of the device,the 1/f noise also changes corresponding to the electrical parameters.Both of them are two different representations of the device degradation caused by trapped charges.1/f noise can reflect the characteristics of the density and number of traps inside the device.It can be used for devices of the same material and size without irradiation and other destructive experiments.By measuring the 1/f noise before irradiation,it can be obtained by testing and screening.Batches of devices with better radiation resistance.Finally,a method is proposed to improve the radiation resistance of the device by changing the doping method.Simulation verification shows that this method can better resist the total dose effect.