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Neutron-Induced Multiple-Bit Upset Alan D. Tipton 1, Jonathan A. Pellish 1, Patrick R. Fleming Neutron-Induced Multiple-Bit Upset Alan D. Tipton 1, Jonathan A. Pellish 1, Patrick R. Fleming 1, Ronald D. Schrimpf 1, 2, Robert A. Reed 2, Robert A. Weller 1, 2, Marcus H. Mendenhall 3 1. Vanderbilt University, Department of Electrical Engineering and Computer Science, Nashville, TN 2. Vanderbilt University, Institute for Space and Defense Electronics, Nashville, TN 3. Vanderbilt University, W. M. Keck Free Electron Laser Center, Nashville, TN MURI 2007 alan. [email protected] edu 1

Update • Objective • Results overview – Model multiple-bit – MBU for neutron upset Update • Objective • Results overview – Model multiple-bit – MBU for neutron upset for 90 nm CMOS irradiation exhibits an technology angle dependence – Calibrate to – MBU for neutron experimental neutron irradiation exhibits data frontside/backside dependence • Status • Future work – Device description created – Begin modeling of 65 nm technology – Simulation is good agreement with – Characterize impact of experimental data angular dependence on error rate MURI 2007 alan. [email protected] edu 2

Outline • Background – Multiple-bit upset (MBU) – Neutron-induced MBU • Modeling – Monte-Carlo Outline • Background – Multiple-bit upset (MBU) – Neutron-induced MBU • Modeling – Monte-Carlo Radiative Energy Deposition (MRED) • Results – Single-bit – Multiple-bit • Conclusion • Future work MURI 2007 alan. [email protected] edu 3

Outline • Background – Multiple-bit upset (MBU) – Neutron-induced MBU • Modeling – Monte-Carlo Outline • Background – Multiple-bit upset (MBU) – Neutron-induced MBU • Modeling – Monte-Carlo Radiative Energy Deposition (MRED) • Results – Single-bit – Multiple-bit • Conclusion • Future work MURI 2007 alan. [email protected] edu 4

Multiple-bit upset increases with scaling • Reliability – Memory design – Testing • Multiple-bit Multiple-bit upset increases with scaling • Reliability – Memory design – Testing • Multiple-bit upset (MBU) has been shown to increase for smaller technologies • Feature size small relative to radiation events MURI 2007 Nucleon-Induced MBU Maiz et al. Tosaka et al. Kawakami et al. Hubert et al. from Seifert, et al. , Intel. IRPS, 2006. alan. [email protected] edu 5

Neutrons induce nuclear reactions • Neutron. Nuclear induced Reaction nuclear reactions • Secondary products Neutrons induce nuclear reactions • Neutron. Nuclear induced Reaction nuclear reactions • Secondary products are ionizing particles that induce soft errors MURI 2007 alan. [email protected] edu Incident Neutron Heavy-Ion Sensitive Nodes 6

Outline • Background – Multiple-bit upset (MBU) – Neutron-induced MBU • Modeling – Monte-Carlo Outline • Background – Multiple-bit upset (MBU) – Neutron-induced MBU • Modeling – Monte-Carlo Radiative Energy Deposition (MRED) • Results – Single-bit – Multiple-bit • Conclusion • Future work MURI 2007 alan. [email protected] edu 7

Modeling methodology • 90 nm SRAM model • Sensitive node Sensitive Node Metallization – Modeling methodology • 90 nm SRAM model • Sensitive node Sensitive Node Metallization – Charge collection volume • Technology Computer Neutron Aided Design (TCAD) Spectrum Model • Simulation - MRED (Monte. Carlo Radiative Energy Deposition) Code • Energy deposition cross section - ED(E) • Multiple node cross section - M(E) MURI 2007 alan. [email protected] edu TCAD MRED ED(E) M(E) 8

MRED irradiated the TCAD device • TCAD structure Copper created from layout lines and MRED irradiated the TCAD device • TCAD structure Copper created from layout lines and process information for a 90 nm SRAM • Device imported into MRED and simulated Tungsten using Los Alamos Neutron Lab (LANL) vias WNR beam line Silicon neutron spectrum bulk MURI 2007 alan. [email protected] edu Single Cell 9

LANL neutron beam • WNR beam spectrum imported into MRED • Fluence comparable to LANL neutron beam • WNR beam spectrum imported into MRED • Fluence comparable to cosmicray neutron fluence B. E. Takala, “The ICE House: Neutron Testing Leads to More Reliable Electronics, ” Los Alamos Science, 30 November 2006. MURI 2007 alan. [email protected] edu 10

MRED simulates ionization and nuclear processes • MRED tracks energy deposition Sensitive through all MRED simulates ionization and nuclear processes • MRED tracks energy deposition Sensitive through all Nodes layers • Energy deposition at each sensitive node is calculated MURI 2007 alan. [email protected] edu Cell Array n+Si C+3 n+2 p++3 11

Outline • Background – Multiple-bit upset (MBU) – Neutron-induced MBU • Modeling – Monte-Carlo Outline • Background – Multiple-bit upset (MBU) – Neutron-induced MBU • Modeling – Monte-Carlo Radiative Energy Deposition (MRED) • Results – Single-bit – Multiple-bit • Conclusion • Future work MURI 2007 alan. [email protected] edu 12

Energy deposition cross section Charge Generated (f. C) • ED(E) Cross section to deposit Energy deposition cross section Charge Generated (f. C) • ED(E) Cross section to deposit at least E in the sensitive volume • Relationship to SEU cross section SEU = ED (Qcrit) Energy Deposited (Me. V) MURI 2007 alan. [email protected] edu 13

Single volume energy deposition • ED(E) is the corresponding cross section to deposit energy Single volume energy deposition • ED(E) is the corresponding cross section to deposit energy E or greater in a single sensitive volume • Exhibits a slight angle dependence – Shape of sensitive volume MURI 2007 Charge Generated (f. C) 0° 45° 90° Energy Deposited (Me. V) alan. [email protected] edu 14

Frontside vs backside • Backside shows increased cross section MURI 2007 alan. tipton@vanderbilt. edu Frontside vs backside • Backside shows increased cross section MURI 2007 alan. [email protected] edu 15

Multiple volume energy deposition • MBU 2 or more physically adjacent bits • M(E) Multiple volume energy deposition • MBU 2 or more physically adjacent bits • M(E) is the corresponding cross section to deposit energy E or greater in multiple volumes • Exhibits a slight angle dependence – Cell spacing – Kinematics of reaction products MURI 2007 Charge Generated (f. C) 0° 45° 90° Energy Deposited (Me. V) alan. [email protected] edu 16

Multiple bit multiplicity • MBU characterized for bit multiplicity • Probability of an event Multiple bit multiplicity • MBU characterized for bit multiplicity • Probability of an event decreases with increasing multiplicity #Events(multiplicity) fluence MURI 2007 alan. [email protected] edu 17

The fraction of MBU exhibits an angle dependence • Fraction of MBU (# of The fraction of MBU exhibits an angle dependence • Fraction of MBU (# of MBU events) (# of upset bits) • Fraction of MBU increases for neutrons at grazing angles • Testing and error calculations must account for angular dependencies MURI 2007 alan. [email protected] edu 18

Conclusion • Multiple-bit upset is increasing for highly-scaled devices • Neutron irradiation has been Conclusion • Multiple-bit upset is increasing for highly-scaled devices • Neutron irradiation has been modeled using MRED for a 90 nm CMOS technology • Cross section differs between frontside and backside irradiation • Fraction of MBU exhibits an angle dependence for neutron irradiation – Fraction increases at grazing angles – Neutron testing must account for these dependencies MURI 2007 alan. [email protected] edu 19

Future work • Finish 90 nm work and publish findings – Model 90 nm Future work • Finish 90 nm work and publish findings – Model 90 nm experimental neutron data • Begin work on 65 nm technology – Create process and design based model – Proton and heavy-ion testing Fall/Winter 2007 – Examine impact of angular dependence on error rate MURI 2007 alan. [email protected] edu 20