How Can Chips Live Under Radiation?
Interactions of different types of radiation in silicon are discussed together with effects on devices. Long-term irradiations cause ‘Total-Ionization-Dose’ degradation and ‘Single Event Effects’ occur when dense ionization upsets a small area in a chip.
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How Can Chips Live Under Radiation? Erik H.M. Heijne
Abstract Interactions of different types of radiation in silicon are discussed together with effects on devices. Long-term irradiations cause ‘Total-Ionization-Dose’ degradation and ‘Single Event Effects’ occur when dense ionization upsets a small area in a chip. At the CERN Large Hadron Collider LHC we expect a severe radiation environment, yet sophisticated chips are needed. Some remedies against radiation effects are illustrated. One can use changes in technology, in device geometry, in circuit design or in layout. At system level one can recover loss of functions or data. Trends in CMOS technology call for continuous study of behaviour of new devices under radiation. The increased use of chips for critical functions everywhere imposes study of rare effects of radiation, not only in extreme conditions. With large areas of silicon in operation worldwide, low probabilities do result in real incidents.
11.1
Introduction
Radiation of all kinds generates free charge carriers in semiconductors, as long as the energy of the incident quantum exceeds the bandgap energy. This can be desirable, as in an imager or a solar cell, or very bad if the radiation upsets the normal device functions. Semiconductor devices have been introduced just a couple of years after the second world war, and military and space applications soon suffered from this problematic sensitivity to radiation. A series of yearly conferences started, the Nuclear and Space Radiation Effects Conference NSREC, reported in the Transactions on Nuclear Science of the IRE, later IEEE, and these continue today. A specialized industry developed for the supply of adequately hardened circuits for E.H.M. Heijne (*) CERN PH Department, CH1211 Gene`ve 23, Switzerland IEAP-CTU, Prague, Czech Republic NIKHEF, Amsterdam, The Netherlands e-mail: [email protected] A.H.M. van Roermund et al. (eds.), Nyquist AD Converters, Sensor Interfaces, 203 and Robustness: Advances in Analog Circuit Design, 2012, DOI 10.1007/978-1-4614-4587-6_11, # Springer Science+Business Media New York 2013
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Fig. 11.1 Average values of cosmic ray particles at sea level, 45 geomagnetic latitude, from Ziegler [2]. Large variations with time and place are possible
this class of users. The earliest spectacular, radiation–related, public incident was the failure of the TELSTAR communication satellite, soon after its launch in 1962. Civilian applications of devices and integrated circuits at first appeared unaffected, until ~1975 it was discovered that alpha particle impact could change the state of semiconductor memory cells [1]. In 1979 James Ziegler at IBM showed that also sea level cosmic rays could influence silicon devices [2]. He concluded that the technology had just gone over a threshold in miniaturization, beyond which the radiationgenerated charge becomes comparable with the charges that determine the function of the device. Ever since, radiation has, or should have been a concern in the operation of integrated circ
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