| In 2000,the team of Professor Hu Zhengming of the University of California,Berkeley proposed the FDSOI transistor structure.Together with the Fin FET transistor concept proposed by the team in 1999,it was considered to be able to overcome the transistor feature size,reduce the gate-to-device and control the attenuation to make the CMOS process.In 2006,the 28 nm FDSOI CMOS transistor developed by European semiconductor research institutions and companies in the laboratory was successful,and mass production was achieved in 2012,and the mass production of 22 nm FDSOI CMOS transistor was achieved in 2017.FDSOI CMOS transistors have the characteristics of high threshold voltage control accuracy,small leakage current,low soft error rate and small parasitic capacitance,and are promising in high-reliability fields such as automotive electronics and aerospace.Among the factors that affect the reliability of MOS transistors,radiation effect has a non-negligible effect on the function and performance of devices,and radiation is everywhere.From the outer space of the atmosphere to the surface,there are charged high-energy particles such as protons,helium ions,electrons,and highly charged ions.These particles produce air spraying when they encounter air molecules in the atmosphere,generating X-rays,protons,mesons,and electrons.Neutrons,helium ions and other ionizing radiation waves and particles.There are also helium ions,electrons,gamma rays produced by the decay of radioisotopes.All ionizing radiation will affect MOS transistors.According to different physical mechanisms,it can be divided into two types,total dose effect and single particle effect.The phenomenon that the dose accumulation of ionizing radiation with small energy that causes the MOS transistor parameters to drift is called the total radiation dose effect.Under gamma irradiation,when the dose accumulated to 100 krad(Si),the threshold voltage drift of the experimental FDSOI MOS transistor mostly reached 10%,the failure threshold,which is related to the lower threshold voltage.The voltage drift is about 30 m V in low threshold voltage transistors,which is a larger proportion of drift than that of regular transistors,which is also related to the introduction of the buried oxide layer to accumulate the dielectric charge that change the threshold voltage of the transistor.The phenomenon that the threshold voltage of the N-type MOS transistor drifts to the negative direction is deteriorated.At the same time,the dielectric charge of the buried oxide layer also degrades the adjustment function of the back-gate bias voltage to the threshold voltage of the device.The phenomenon that a single high-energy particle causes transient circuit malfunction or damage in a CMOS circuit is called the single particle effect.Because the FDSOI MOS transistor has a buried oxide layer to block the conduction path of the body charge,it can be immune to the transient effects generated by the body excited charge,but it is still experimentally found that the charge excited by a single high-energy particle in the thin layer semiconductor can still cause the reversal of node voltage.The significance of this phenomenon is positively related to the operating frequency of the dynamic circuit.This article also found that some of the original methods used to strengthen the radiation resistance of bulk silicon devices are still effective for advanced FDSOI CMOS process transistors. |
