1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T K.124 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2016) SERIES K: PROTECTION AGAINST INTERFERENCE Overview of particle radiation effects on telecommunication systems Recommendation ITU-T K.124 Rec. ITU-T K.124 (12/2
2、016) i Recommendation ITU-T K.124 Overview of particle radiation effects on telecommunication systems Summary Recommendation ITU-T K.124 provides basic guidance on soft errors that are caused by particle radiation and that affect telecommunication systems. This Recommendation details the phenomena o
3、f soft errors that arise from particle radiation. A brief explanation of the procedures for design, test and mitigation measures are also included in this Recommendation. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T K.124 2016-12-14 5 11.1002/1000/13140 Keywords LSI, neut
4、ron, particle radiation, single event upset, soft error. * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T K.124 (12/2016) FORE
5、WORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying
6、 technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups w
7、hich, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO a
8、nd IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (
9、to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such wor
10、ds does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position conc
11、erning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by p
12、atents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2017 All rights reserved. No part of this pu
13、blication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T K.124 (12/2016) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation . 1 4 Abbreviations and acronym
14、s 1 5 Conventions 2 6 Mechanism by which particle radiation causes soft errors . 2 6.1 Particle radiation which causes soft errors . 2 6.2 Effect of geographical conditions and solar activity on soft error rate 5 6.3 The effect of building and installation conditions on soft error occurrence in tele
15、communication equipment . 7 6.4 Types of soft errors . 10 7 Impact of soft errors generated in telecommunication equipment and mitigation methods . 10 7.1 The increase of soft errors in telecommunication equipment 10 7.2 Impact of soft errors on operation of telecommunication systems and mitigation
16、measures 11 7.3 Mitigation measures for soft errors in telecommunication equipment . 13 8 Necessity of this Recommendation for soft errors . 14 9 Development procedures for telecommunication equipment . 15 Bibliography. 17 iv Rec. ITU-T K.124 (12/2016) Introduction As more highly integrated semicond
17、uctor devices are deployed in telecommunication equipment, soft errors caused by particle radiation occur more frequently on carrier telecommunication networks and have a more severe impact on network operations and the quality of signal transmission. Accordingly, measures to mitigate the effect of
18、soft errors are required for telecommunication equipment. A large amount of telecommunication equipment is installed in remotely supervised telecommunication networks. A single soft error within a piece of telecommunication equipment can have a disastrous impact on services if the equipment is not a
19、ppropriately designed to mitigate the effect of soft errors. Therefore, it is important during the design and development of telecommunication equipment to determine the impact of soft errors and to apply additional measures to mitigate this impact in order to achieve the target quality of the syste
20、m. Rec. ITU-T K.124 (12/2016) 1 Recommendation ITU-T K.124 Overview of particle radiation effects on telecommunication systems 1 Scope This Recommendation presents an overview of the effects of particle radiation and design methods to mitigate the impact of soft errors. The Recommendation is applica
21、ble to the telecommunication equipment that composes a terrestrial carrier telecommunication network, including core network equipment (i.e., link and node equipment) and access network equipment that are installed in telecommunication centres. 2 References The following ITU-T Recommendations and ot
22、her references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encourage
23、d to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone documen
24、t, the status of a Recommendation. None. 3 Definitions 3.1 Terms defined elsewhere None. 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 neutron irradiation test : A means to evaluate soft error quality through the use of neutron irradiation emitted by
25、 a neutron source driven by a compact accelerator. 3.2.2 soft error: A phenomenon in which one or more bits within the data on the device have their values reversed. A soft error does not constitute damage to the actual semiconductor device. 3.2.3 soft error rate: Occurrence number of soft error in
26、a unit time. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: CRAM Configuration Random Access Memory DICE Dual Interlocked Storage Cell ECC Error Correction Code EUT Equipment under test FIT Failure In Time FPGA Field-Programmable Gate Array LSI Large
27、Scale Integration 2 Rec. ITU-T K.124 (12/2016) MCU Multiple Cell Upset NE Network Equipment RCC Replication, Comparison, Checkpointing SCU Single Cell Upset SEB Single-Event Burnout SEL Single-Event Latch-up SEU Single-Event Upset SRAM Static Random Access Memory TMR Triple Modular Redundancy 5 Conv
28、entions None 6 Mechanism by which particle radiation causes soft errors A soft error does not damage the semiconductor device itself; instead it is a phenomenon that affects the data within the device by reversing the value of one or more bits within the data. The semiconductor device itself is not
29、damaged, therefore its operation will be restored to normal operation condition after the reversed bit is rewritten to the device or the semiconductor device is initialized in order to reset the data in memory to its default values. This Clause will explain the phenomena that produces particle radia
30、tion, which is the cause of soft errors, as well as the mechanism by which soft errors occur in semiconductor devices. 6.1 Particle radiation which causes soft errors Soft errors are mainly caused by particle radiation of neutrons and alpha particles. Neutrons are generated by cosmic rays and alpha
31、particles are generated by minute quantities of radioisotopes contained in materials used within the semiconductor devices. 6.1.1 Mechanism by which alpha particles cause soft errors Materials for the packages and wiring that compose an integrated circuit contain minute quantities of radioisotopes s
32、uch as uranium238 or thorium232. When an alpha particle produced by the radioisotope invades the interior of the material used in an integrated circuit, electron hole pairs are generated along the path of the alpha particle as shown in Figure 6-1. The electron hole pairs generated in and around the
33、depletion layer drift and accumulate within the memory cell. Once the accumulated charge exceeds a threshold level specific to the semiconductor gate, the value of the bit within the memory cell is reversed (from 0 to 1 or 1 to 0). The occurrence of soft errors caused by alpha particles can be reduc
34、ed by using high purity materials such as low alpha particle plastics. Rec. ITU-T K.124 (12/2016) 3 Figure 6-1 Invasion of alpha particles in semiconductor material causes soft errors 6.1.2 Mechanism by which cosmic rays cause soft errors Ultra-high energy particles are included in cosmic rays that
35、are flying about in cosmic space. As shown in Figure 6-2, two types of cosmic rays cause soft errors: solar cosmic rays produced by solar activity and galactic cosmic rays that originate outside of the solar system. Both types of cosmic rays are composed of such elements as electrons, protons and al
36、pha particles. As cosmic rays enter the atmosphere of the earth, they collide with nuclei in the atmosphere and cause a nuclear reaction that produces secondary particles such as neutrons, -mesons, electrons and protons. Unlike other types of particles, the energy and flux density of neutrons during
37、 travel in the atmosphere is not significantly reduced because a neutron does not have an electric charge. The energy spectrum of neutrons at the earths surface is shown in Figure 6-3. The mechanism by which neutrons generate soft errors in semiconductor devices differs depending upon neutron energy
38、. High-speed neutrons with energy of 1 MeV or higher cause nuclear reactions with the silicon nuclei in the semiconductor chip and the secondary ions produced in these reactions cause soft errors. Thermal neutrons with energy of around 25 meV cause a capture reaction with the 10B within the semicond
39、uctor device and generate alpha particles, which cause the soft error. Figure 6-4 shows the mechanism by which high-speed neutrons cause soft errors. The collision of a high-speed neutron with an atom in the chip material (such as a silicon atom) has some probability of causing a nuclear reaction an
40、d when such a reaction occurs it generates secondary ions. Electron hole pairs are generated along the path of the secondary ions in the chip and a soft error occurs. 4 Rec. ITU-T K.124 (12/2016) Figure 6-2 Cosmic rays Figure 6-3 High-energy neutron spectrum at sea level in New York City b-JEDEC Rec
41、. ITU-T K.124 (12/2016) 5 Figure 6-4 Invasion of high-energy neutron causing soft errors 6.2 Effect of geographical conditions and solar activity on soft error rate The flux level of neutrons from space differs depending on such factors as geographical conditions (i.e., location on the earth and alt
42、itude) and solar activity and has an effect on the probability of generating soft errors. Neutron flux is higher at higher altitudes since neutrons are generated within the atmosphere at high altitudes and reduced in number as they travel to lower altitude locations. The relationship between neutron
43、 flux and altitude is shown in Figure 6-5. The path of high energy protons in the cosmic rays that generate neutrons in the atmosphere is affected by the magnetic field since the high energy proton has a positive charge. The neutron flux generated by cosmic rays is lower at locations closer to the e
44、quator since the repulsive force of the magnetic field produced by geomagnetism is stronger and cosmic rays are repelled more. Conversely, the flux level at high latitudes near the North and South poles is higher since the repulsive force is weaker there. The ratio of neutron flux at major world cit
45、ies compared to that of New York as a reference is shown in Table 6-1. Neutron flux level also depends on solar activity, which periodically changes between high and low levels at an approximately 11-year cycle. During periods of high solar activity, less neutron flux is observed on the earth since
46、solar magnetic flux, which reduces the amount of galactic cosmic radiation entering the solar system, is stronger than in other periods. In the event of a largescale solar flare, the amount of neutron flux shows a temporary spike because the emitted solar cosmic radiation increases enormously at the
47、 time of such an event. The change in sunspot number and neutron flux is shown in Figure 6-6, which shows that solar activity increases when sunspot number decreases. The level of neutron flux depending on geographical conditions as well as solar activity can be obtained by computer simulations of f
48、lying path of galactic rays and their reaction upon collision with atmospheric gases. As a result, the occurrence of soft errors for a specific location and degree of solar activity can be evaluated based on the ratio of cosmic-ray neutron flux versus the reference level at New York. 6 Rec. ITU-T K.
49、124 (12/2016) Figure 6-5 Neutron flux variation with altitude Table 6-1 Ratio of cosmic-ray neutron flux level in cities relative to New York b-JEDEC City or location Latitude () Longit ( E) Elevat. (m) Atm. Depth (g/cm2) Cutoff Rigidity (GV) Relative Neutron Flux Active Sun Low Quiet Sun Peak Avg. Bangkok, Thailand 13.4N 100.3 20 1031 17.4 0.51 0.53 0.52 Beijing, China 39.9N 116.4 55 1027 9.4 0.71 0.76 0.73 Berlin, Germany 52.5N 13.4 40 1028 2.8 0.94 1.08 1.01 Bogot, Colombia 4.6N 285.9 2586 753 12.3 3.7 4 3.85 Chicago, IL, USA 41.9N 272.4 180 1011 1.8 1.0
