Research On Electrical Stress And Total Dose Radiation Coupling Effect Of Nano-MOS Devices

Since the transistor was developed,it has played an irreplaceable role in all walks of life and has had a profound impact on people's lives.At the same time,due to the constant replacement of transistor manufacturing technology and people's increasingly high requirements for transistor performance,transistors are being scaled down in accordance with Moore's Law.At present,the size of integrated circuits has been reduced to the nanometer range,reaching a process node of several nanometers.Due to the size reduction,the internal electric field of the device will increase,which will have a greater impact on the reliability of the device.Moreover,MOS devices that have been working in a radiation environment for a long time will also be irradiated by rays to produce defects inside the device,forming a total dose effect and causing device failure.This article uses a combination of simulation and experiment to analyze the MOSFET electrical stress and total dose radiation coupling effect in depth.Firstly,the 28nm PMOSFET is simulated,and the electrical stress related model is used to analyze the impact of electrical stress on PMOS devices through software.It is found that after a negative gate voltage is applied,the threshold voltage of the PMOSFET shifts negatively,and the absolute value of the threshold voltage increases,which indicates that a positive interface trap is generated at the Si/SiO₂ interface;the potential in the channel region decrease with the stress time increase,which weakens the control effect of the gate.At the same time,the concentration of H atoms and H₂in each time period was extracted,and it was found that the concentration of H atoms was not linear between 10^-6s?10s,but showed a linear relationship after 10s;the concentration of H₂ was positively correlated with stress time within 10s,H₂ diffuses after 10s,and the degree of diffusion is negatively correlated with time.Under the same stress time,the fracture rate of the Si-H bond is proportional to the rate of formation of interface traps,and the rate of repassivation is inversely proportional to the rate of formation of interface traps.In addition,the influence of high temperature and strong field on the threshold voltage shift is also simulated,and it is found that as the electric field or temperature increases,the threshold voltage shift increases.Secondly,the 28nm NMOSFET was subjected to electrical stress experimental analysis.Under the positive gate voltage,the threshold voltage shifted in the positive direction,indicating that the combined effect of the interface trap and the oxide layer charge is negative.According to the modified model,the trap charge concentration is calculated,which is in good agreement with the actual test results.In terms of noise,the noise of the stressed NMOS device near the threshold voltage becomes larger,the noise is more sensitive to the trap,and the trap energy distribution is more uniform after the stress.In the comparison of different sizes,it is found that for devices with the same gate length,the wider the gate width,the greater the threshold voltage shift,which is mainly related to the uneven distribution of oxygen vacancies;for devices with the same gate width,the shorter the gate length,the greater the threshold voltage shift,which is mainly related to the gate edge effect.Finally,the influence of the coupling effect of electrical stress and total dose radiation on MOS devices is studied.It is found that the combined effect of electrical stress and radiation reduces the degradation of characteristic parameters such as threshold voltage,and the radiation effect weakens the final degradation of the device.One of the reasons is that the electrons introduced by the radiation effect will destroy part of the hydrogen(H)bonds,and the H bonds also play an important role in the process of electrical stress.Secondly,in the process of applying positive gate stress,electrons tunnel into the oxide layer,neutralizing part of the positive charge generated during the radiation process,which also reduces the degradation of the device.In terms of structure,the radiation effect will generate a parasitic gate in the STI region,and the influence of the parasitic gate on the threshold voltage increases as the gate width decreases.In this paper,the electrical stress simulation and experimental study of 28nm process MOSFET are carried out,and the coupling effect between the electrical stress and the total dose effect is compared and analyzed.The research results provide theoretical guidance for the anti-radiation reliability.