The Prediction And Research Of The Single Event Effect Of Photon Based On GEANT4

With the rapid development of space technology, more and more integrated circuit components have been applied to all kinds of avionics system. However, a large number of high-energy particles in the space environment, such as protons, heavy ions, gamma rays, etc., will induce the semiconductor devices to produce the single event effect which will have a significant impact on the reliability of electronic devices. Especially with the continuous improvement of integrated circuit technology, in the orbiting spacecraft reliability and service life. Single event effect has become an important factor that affects the reliability and service life of spacecraft.We usually use the cross sections and the effective LET threshold to assess the anti-single event effect of semiconductor devices. The radiation experiment method is commonly used to evaluate the anti-single event effect, but it costs too much, is not easy to operate, and can’t evaluate the anti-single event effect of device which is still in the design stage. Therefore, researchers at home and abroad have adopted various means to study the anti-single event effect of device, expecting to find a reliable method which is easy to operate, is not cost too much, and can predict the anti-single event effect of device that is still in the design stage.Based on the limitations of the existing prediction methods of anti-single event effect. This paper introduces an effective method which is developed by TCAD and Geant4 to evaluate the single event upset of SRAM. The method uses photons to simulate, and obtain the saturated cross section and the critical LET. The main research work of this paper is as follows:1. In this paper, the main radiation effects of device and various space radiation environment are briefly introduced. The physical mechanism of the single event effect of photons and heavy ions are described in detail, and the similarities and differences between the two are compared with. Taking 6T SRAM for example, we analyze the mechanism of SEU in detail; This paper focuses on the RPP model and the multiple sensitive volume model, and the advantages and disadvantages of both are compared with.2. According to the existing empirical formula, on the condition of linear absorption the equivalent LET(linear energy transfer) formula for laser pulse is deduced. In this article, we have modified the calculation formula by considering the influences of nonlinear absorption effect, reflection and refraction on device surface and other factors. Finally, a practical example is used to verify the correctness of the equivalent LET formula, and the reason of the deviation is analyzed in detail.3. The structure, physical characteristics and the principle of hybrid simulation of TCAD software are introduced in detail in this paper. The 3D modeling and calibration of 45 nm SRAM by TCAD software is described in detail. The center of drain region of the cut-off NMOS is perpendicularly radiated by heavy ions with different LET, record the LET of heavy ions when the voltage of drain node just inverts, so this LET is the critical LET of NMOS, the corresponding effective charge collected by the drain node is the critical charge of SEU. By changing the incident position of heavy ions, we extract the geometric parameters and sensitivity coefficients of the multiple sensitive volume, which are necessary for Geant4 simulation.4. Based on the Geant4 software, the materials of detector, geometry, physical process of photon transportation, primary photons and other parameters are defined; Based on the effective charge which is collected by drain sensitive node, the module of SEU judgment is developed, and the number of events cycle is set up, and the number of SEU is counted. By Geant4 simulation, the SEU cross section of different energy photons is obtained, the ?-LET curve is acquired by the curve fitting of Weibull function. The obtained simulation curve is compared with the experimental results of heavy ions accelerator, and the possible reasons for the deviation are analyzed. Through the study of the metal interconnect layer covered on the surface of the device, it is indicated that the metal interconnection layer has a certain shielding effect on the energy of the photons.