This paper provides a historical review of the literature on the effects of radiation-induced displacement damage in semiconductor materials and devices. Emphasis is placed on effects in technologically important bulk silicon and silicon devices. The primary goals are to provide a guide to displacement damage literature, to offer critical comments regarding that literature in an attempt to identify key findings, to describe how the understanding of displacement damage mechanisms and effects has evolved, and to note current trends. Selected tutorial elements are included as an aid to presenting the review information more clearly and to provide a frame of reference for the terminology used. The primary approach employed is to present information qualitatively while leaving quantitative details to the cited references. A bibliography of key displacement-damage information sources is also provided.

Review of displacement damage effects in silicon devices

CREME96 is an update of the Cosmic Ray on Micro-Electronics code, a widely-used suite of programs for creating numerical models of the ionizing-radiation environment in near-Earth orbits and for evaluating radiation effects in spacecraft. CREME96, which is now available over the World-Wide Web (WWW) at http://crsp3.nrl.navy.mil/creme96/, has many significant features, including: (1) improved models of the galactic cosmic ray, anomalous cosmic ray, and solar energetic particle ("flare") components of the near-Earth environment; (2) improved geomagnetic transmission calculations; (3) improved nuclear transport routines; (4) improved single-event upset (SEU) calculation techniques, for both proton-induced and direct-ionization-induced SEUs; and (5) an easy-to-use graphical interface, with extensive on-line tutorial information. In this paper we document some of these improvements.

CREME96: A Revision of the Cosmic Ray Effects on Micro-Electronics Code

The use of nonionizing energy loss (NIEL) in predicting the effect of gamma, electron, and proton irradiations on Si, GaAs, and InP devices is discussed. The NIEL for electrons and protons has been calculated from the displacement threshold to 200 MeV. Convoluting the electron NIEL with the slowed down Compton secondary electron spectrum gives an effective NIEL for CO/sup 60/ gammas, enabling gamma-induced displacement damage to be correlated with particle results. The fluences of 1 MeV electrons equivalent to irradiation with 1 Mrad(Si) for Si, GaAs, and InP are given. Analytic proton NIEL calculations and results derived from the Monte Carlo TRIM agree exactly, as long as straggling is not significant. The NIEL calculations are compared with experimental proton and electron damage coefficients using solar cells as examples. A linear relationship is found between the NIEL and proton damage coefficients for Si, GaAs, and InP devices. For electrons, there appears to be a linear dependence for n-Si and n-GaAs, but for p-Si there is a quadratic relationship which decreases the damage coefficient at 1 MeV by a factor of approximately 10 below the value for n-Si. >

Damage correlations in semiconductors exposed to gamma, electron and proton radiations

Trends in terrestrial neutron-induced soft-error in SRAMs from a 250 nm to a 22 nm process are reviewed and predicted using the Monte-Carlo simulator CORIMS, which is validated to have less than 20% variations from experimental soft-error data on 180-130 nm SRAMs in a wide variety of neutron fields like field tests at low and high altitudes and accelerator tests in LANSCE, TSL, and CYRIC. The following results are obtained: 1) Soft-error rates per device in SRAMs will increase x6-7 from 130 nm to 22 nm process; 2) As SRAM is scaled down to a smaller size, soft-error rate is dominated more significantly by low-energy neutrons (<; 10 MeV); and 3) The area affected by one nuclear reaction spreads over 1 M bits and bit multiplicity of multi-cell upset become as high as 100 bits and more.

Impact of Scaling on Neutron-Induced Soft Error in SRAMs From a 250 nm to a 22 nm Design Rule

The occurrence of single-event upset (SEU) in aircraft electronics has evolved from a series of interesting anecdotal incidents to accepted fact. A study completed in 1992 demonstrated that SEUs are real, that the measured in-flight rates correlate with the atmospheric neutron flux, and that the rates can be calculated using laboratory SEU data. Once avionics SEU was shown to be an actual effect, it had to be dealt with in avionics designs. The major concern is in random access memories (RAMs), both static (SRAMs) and dynamic (DRAMs), because these microelectronic devices contain the largest number of bits, but other parts, such as microprocessors, are also potentially susceptible to upset. In addition, other single-event effects (SEEs), specifically latch-up and burnout, can also be induced by atmospheric neutrons.

Single-event effects in avionics

The authors review various single event effects (SEE) testing and rate prediction methodologies and recommend standard approaches. This discussion is limited to single event upset (SEU) rate prediction for direct-ionization-induced effects. The standard approach being recommended is based partially on a different way of viewing the results of SEU cross-section measurements. The measurements are not measuring a distribution of cross-sections. They are measuring a distribution of device sensitivities, due to differences of sensitive region critical charges and to differences of charge collection. The linear energy transfer (LET), at which 50% of the cell population upsets, corresponds to the charge deposition necessary to upset the median cell in the circuit array. The threshold LET corresponds to the most sensitive region being hit in its most sensitive location, and does not represent the entire array. The shape of the cross-section curve is described by an integral Weibull distribution. The upset rate for a device should then be calculated using the differential rate of each sensitive region, combined with an integral weighting given by the Weibull distribution that describes the measured cross-section curve. >

Rate prediction for single event effects-a critique

Examines a number of possible geometrical effects that may show up in either upset measurements or upset calculations. The geometrical effets are with respect to a number of unusual experimental measurements, and an attempt is made to fit these results into a common set of concepts. In most cases, the results will not be decisive and there will still be room for alternative analysis. In some of these cases, it may be necessary to perform detailed charge collection or microbeam experiments in order to reach closure. However, the authors believe that the concepts and questions that they introduce are fundamental for a complete understanding of single event upsets in modern devices. In particular, they continue to maintain that the basic upset cross section curve can be represented by a single smooth curve. They summarize the knowledge of the funnel effect and indicate approaches for including the funnel in upset rate predictions. >

Geometrical factors in SEE rate calculations

High-energy knock-on atoms produced by incident protons are much more important in determining the total nonionizing energy deposited in GaAs than in Si, due to the relative size of the Lindhard correction for partitioning the recoil energy. High-energy recoils are mainly produced by inelastic nuclear interactions between the incident protons and the target atoms. A review of previous calculations indicates that both the fast cascade and the evaporation phases of the elastic interaction contribute to the average energy of the recoiling ion. New calculations are presented for the energy dependence of the nonionizing energy deposited in GaAs as a result of inelastic interaction with protons over the energy range 10-1000 MeV. These calculations are combined with the previously determined contribution from elastic interactions to obtain the energy dependence of the total nonionizing energy deposited in GaAs by protons. The calculation is compared with both new and earlier experimental data for ion-implanted GaAs resistors irradiated with protons over the energy range 40-188 MeV, in order to form a basis whereby proton displacement effects in GaAs structures can be predicted. It is shown that results obtained for 10 MeV protons, for example, can be used to predict results to be expected at much higher energies. >

Displacement damage in GaAs structures

The Small Explorer Data System (SEDS) is a spaceflight command and data handling system for the small explorer (SMEX) program at Goddard Space Flight Center (GSFC). A key component in this system is the SEDS MIL-STD-1773 Fiber Optic Multiplexed Data Bus. The 1773 bus provides a means of passing telemetry and commands between spacecraft subsystems. This bus is currently being considered for additional spaceflight programs inside and outside of the NASA realm. The SEDS 1773 bus uses integrated optoelectronics as part of its electrical subsystem (or user) to optical interface. Generic proton and heavy ion test results have been previously reported. Herein is presented proton test results for continuing this investigation under actual subsystem interface conditions (MIL-STD-1773) as well as for generic devices using the proton test facilities at University of California, Davis (UCD). This testing was undertaken as a joint effort between NASA/GSFC and the Naval Research Laboratories (NRL).

E.L. Petersen

Papers

CREME96: A Revision of the Cosmic Ray Effects on Micro-Electronics Code

Rate prediction for single event effects-a critique

Geometrical factors in SEE rate calculations

Displacement damage in GaAs structures

Proton irradiation SEU test results for the SEDS MIL-STD-1773 fiber optic data bus: integrated optoelectronics