| With the development and strategic requirement of national aerospace industry,the radiation response of underlying integrated circuits and semiconductor devices todifferent radiation environment has been widely studied and investigated in the fieldof radiation effects and the related radiation-hardened technology project. Singleevent effects (SEEs), as a vital factor to result in parametric degradation or functionalfailure in devices exposure to radiation resources, has been concerned andinvestigated in areas of defense and space navigation. The currently usedsemiconductor devices are mainly in the technological scale of Micro/Nano, whichare more sensitive to the SEEs susceptibility than that of conventional sizes. Forinstance, edge effect within SEEs becomes more serious when the device features arescaling down to Micro/Nano, and the ion profile and device internal property hasessential influence on the SEEs.This dissertation has characterized, examined and analyzed the single event upsetsensitivity of static random access memories (SRAMs) of Micro/Nano scales and theunderlying physical mechanism, based on the theoretical model/computer simulation.The main research approaches and results of this dissertation are as follows,(1) The MUlti-Functional Package for SEEs Analysis (MUFPSA) has beensuccessfully constructed to characterize the SEEs evaluation and assessment. Wehave programmed the package to approach the performance including thevariances of ion-beam profile, device property, physical process, etc. Based on theGEANT4, it is necessary to point out that advantages of MUFPSA are mainlypresented about integration of classical model of Rectangular Paralleled-piped (RPP) and charge diffusion-collection process, flexibility for altering devicegeometry, SRAMs array construction and detection of multiple-bit upset (MBU)probability/multiplicity. With the aid of MUFPSA, the devices applied inaerospace can be evaluated and assessed in advance, and these correspondingresults als provide the supplemental evidences and theoretical guidance for SEEscharacterization.(2) Influence of the dimensions of sensitive volume (SV) on single event upset (SEU)occurrence have been identified and the edge effect aroused by it at obliqueincidence has been quantified as the difference of deposited energy between theincident way of randomly strike and traverse on the center of SV. It is proven thatthe SEU rate predictiondepends to some extent on the dimensions of SV, butconcerning the funnel effect, it is more likely rely on the specific property ofdevice. In addition, the difference of deposited energy induced by differentincident ways has been quantitatively and qualitatively investigated on thecondition that the size varied at the vertical and horizontal direction. The resultsshow that, a) the on-orbit SEU rate of aerospace semiconductor devices has thedependence on the dimensions of SV. Additionally, it is noted that the parameterof P should be taken into consideration when using the RPP model to predict theSEU rates. As the thickness of depletion layer is ranged from0to4μm, tomitigate the serial errors from the LET, the parameter of P should be selected asno less than1and hence the SEU rate prediction is more accurate and reasonable.The hypothetical length of funnel relys on the device structure and internalparameters; b) the regularity of loss of deposited energy induced by9.5MeV/u209Bi and20MeV/u132Xe respectively are almost identical for a certain surfacearea or thickness variances. However, it is observed that the difference ofdeposited energy is more sensitive to the factor of surface area of SV than to thevariance of thickness, and as increasing the incident angle, the trend of curves inthe sequence of the deposited energy relys more on the surface area. In contrary,the difference of deposited energy becomes terminally saturation in the case of changeable thickness, because of the limited electron-hole density and therestrained critical angle in geometry.(3) The relationship between SEU susceptibility in SRAMs within Micro/Nano scalesand ion-beam profile has been modeled. Primarily, we have explored the influencefactors about critical charge, distance between adjacent cells and over-layer onSEU/MBU sensitivity. Moreover, according to the radial profile of ion track, theapplication of LET as a metric for characterizing SEEs has been discussed. Usingthe same value of LET but different species and energy of incident ions todistinguish the radiation response of Micro/Nano scales SRAMs, the results havebeen presented on the single cell and multiple cells, respectively. The results showthat, a) the orientation of ion beams and device with different critical charge exertindispensable effects on MBU. Additionally, with the decrease of spacing distancebetween adjacent cells or the dimensions of the cells, the device is moresusceptible to SEEs, especially to MBU at oblique incidence; b) the influence ofdimensions of device on MBU sensitivity is more involved in device structure,especially its over-layers; c) LET alone is not accurate enough to characterizeSEU because MBU distribution induced by incident ions with the same LET aredifferent, particularly reflected in the MBU probability. Furthermore, twoparameters derived from ion track structure, i.e., track radius and ion relativevelocity, are taken into consideration, which turns out that the ability of incidentions triggering MBUs follows132Xe185.08MeV>209Bi140.63MeV>132Xe1231.33MeV>209Bi7625.26MeV. The explanation is that the lower ion-velocitywould produce higher radial density of e-/h+pairs and hence cause higher chargedensity.(4) The physical mechanisms of proton-induced and heavy ion-induced SEUoccurrence have been incorporated and compared with each other. It isinterestingly noted that the new phenomenon about MBU occurrence has beenobserved in45nm SRAMs, which is further analyzed through energy depositionprofile. From the standpoint of radiation damage, we have bridged theproton-induced and heavy ion-induced SEU occurrence. Based on the common-used on-orbit SEU rate prediction model, the relation of SEEs inducedby proton and heavy ion has been elucidated. It is validated that low-energyprotons have the ability to trigger SEU occurrence, and the new situation aboutMBU occurrence has been deep analyzed. The results show that, a) based on theconsistent of SEU induced by heavy ion and proton, it is observed that the SEUcross section presents the relevance in two saturation curves; b) with theintegration of the SEU rate prediction model, the heavy ion data can be insertedinto the model for equivalently predicting the rate induced by proton; c) the SEUcross-sections on the45nm SRAMs are compared with previous research work,which not only validated the simulation approach used herein, but also expose theexistence of saturated cross-section and the induced MBU when the incidentenergy is less than1MeV.(5) Technical methods for analysis of SEEs micro-mechanism have beensystematically proposed. These approaches are constructed upon the RPP model,including the deposited energy or the dispersion of it, radial ionization profile,traversing time within device, and the fixed model of collected charge at obliqueincidence. The results show that SEEs can be comprehensively characterized bythe combination of above deterministic methods. The employed approachesprovide a deep understanding of the micro-mechanism of SEEs. |
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