Neutron-Induced Multiple-Bit Upset

MURI 2007 [email protected]

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Neutron-Induced Multiple-Bit UpsetAlan D. Tipton1, Jonathan A. Pellish1,Patrick R. Fleming1, Ronald D. Schrimpf1,2,Robert A. Reed2, Robert A. Weller1,2,Marcus H. Mendenhall3

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


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Update• Objective

– Model multiple-bit upset for 90 nm CMOS technology

– Calibrate to experimental neutron data

• Status– Device description created

– Simulation is good agreement with experimental data

• Results overview– MBU for neutron irradiation exhibits an angle dependence

– MBU for neutron irradiation exhibits frontside/backside dependence

• Future work– Begin modeling of 65 nm technology

– Characterize impact of angular dependence on error rate


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Outline• Background

– Multiple-bit upset (MBU)– Neutron-induced MBU

• Modeling– Monte-Carlo Radiative Energy Deposition (MRED)

• Results– Single-bit– Multiple-bit

• Conclusion• Future work


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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

from Seifert, et al., Intel. IRPS, 2006.

Nucleon-Induced MBU

Maiz et al.

Tosaka et al.Kawakami et al.

Hubert et al.


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Neutrons induce nuclear reactions• Neutron-induced nuclear reactions

• Secondary products are ionizing particles that induce soft errors

Incident Neutron

Nuclear Reaction

Heavy-Ion

Sensitive Nodes


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• 90 nm SRAM model• Sensitive node

– Charge collection volume

• Technology Computer Aided Design (TCAD) Model

• Simulation - MRED (Monte-Carlo Radiative Energy Deposition) Code

• Energy deposition cross section - ED(E)

• Multiple node cross section - M(E)

Modeling methodology

MRED

SensitiveNode

ED(E)

Metallization

M(E)

TCADNeutronSpectrum


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MRED irradiated the TCAD device• TCAD structure created from layout and process information for a 90 nm SRAM

• Device imported into MRED and simulated using Los Alamos Neutron Lab (LANL) WNR beam line neutron spectrum Silicon

bulk

Copper lines

Tungsten vias

Single Cell


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LANL neutron beam• WNR beam spectrum imported into MRED

• Fluence comparable to cosmic-ray neutron fluence B. E. Takala, “The ICE House: Neutron Testing Leads to More

Reliable Electronics,” Los Alamos Science, 30 November 2006.


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n+Si

C+3n+2p++3

MRED simulates ionization and nuclear processes

• MRED tracks energy deposition through all layers

• Energy deposition at each sensitive node is calculated

Sensitive Nodes

Cell Array


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Energy deposition cross section

ED(E)Cross section to deposit at least E in the sensitive volume

• Relationship to SEU cross sectionSEU = ED (Qcrit)

Energy Deposited (MeV)

Charge Generated (fC)


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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



0°45°90

°


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Frontside vs backside• Backside shows increased cross section


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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



0°45°90

°


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Multiple bit multiplicity• MBU characterized for bit multiplicity

• Probability of an event decreases with increasing multiplicity

#Events(multiplicity)

fluence


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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


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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


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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

Documents

Neutron-Induced Multiple-Bit Upset