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

In this paper, we describe a Monte Carlo approach for estimating the frequency and character of single event effects based on a combination of physical modeling of discrete radiation events, device simulations to estimate charge transport and collection, and circuit simulations to determine the effect of the collected charge. A mathematical analysis of the procedure reveals it to be closely related to the rectangular parallelepiped (RPP) rate prediction method. The results of these simulations show that event-to-event variation may have a significant impact when predicting the single-event rate in advanced spacecraft electronics. Specific criteria for supplementing established RPP-based single event analysis with Monte Carlo computations are discussed.

Monte Carlo Simulation of Single Event Effects

This document describes the radiation environments, physical mechanisms, and test philosophies that underpin radiation hardness assurance test methodologies. The natural space radiation environment is presented, including the contributions of both trapped and transient particles. The effects of shielding on radiation environments are briefly discussed. Laboratory radiation sources used to simulate radiation environments are covered, including how to choose appropriate sources to mimic environments of interest. The fundamental interactions of radiation with materials via direct and indirect ionization are summarized. Some general test considerations are covered, followed by in-depth discussions of physical mechanisms and issues for total dose and single-event effects testing. The purpose of this document is to describe why the test protocols we use are constructed the way they are. In other words, to answer the question: “Why do we test it that way”?

Radiation Hardness Assurance Testing of Microelectronic Devices and Integrated Circuits: Radiation Environments, Physical Mechanisms, and Foundations for Hardness Assurance

Experimental results are presented on single-bit-upsets (SBU) and multiple-bit-upsets (MBU) on a 45 nm SOI SRAM. The accelerated testing results show the SBU-per-bit cross section is relatively constant with technology scaling but the MBU cross section is increasing. The MBU data show the importance of acquiring and analyzing the data with respect to the location of the multiple-bit upsets since the relative location of the cells is important in determining which MBU upsets can be corrected with error correcting code (ECC) circuits. For the SOI SRAMs, a large MBU orientation effect is observed with most of the MBU events occurring along the same SRAM bit-line; allowing ECC circuits to correct most of these MBU events.

Single-Event Upsets and Multiple-Bit Upsets on a 45 nm SOI SRAM

Experimental data are presented that show low-energy muons are able to cause single event upsets in 65 nm, 45 nm, and 40 nm CMOS SRAMs. Energy deposition measurements using a surface barrier detector are presented to characterize the kinetic energy spectra produced by the M20B surface muon beam at TRIUMF. A Geant4 application is used to simulate the beam and estimate the energy spectra incident on the memories. Results indicate that the sensitivity to this mechanism will increase for scaled technologies.

Muon-Induced Single Event Upsets in Deep-Submicron Technology

Direct ionization from low energy protons is shown to cause upsets in a 65-nm bulk CMOS SRAM, consistent with results reported for other deep submicron technologies. The experimental data are used to calibrate a Monte Carlo rate prediction model, which is used to evaluate the importance of this upset mechanism in typical space environments. For the ISS orbit and a geosynchronous (worst day) orbit, direct ionization from protons is a major contributor to the total error rate, but for a geosynchronous (solar min) orbit, the proton flux is too low to cause a significant number of events. The implications of these results for hardness assurance are discussed.

A. D. Tipton

Papers

Impact of Low-Energy Proton Induced Upsets on Test Methods and Rate Predictions