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### Neutron-Induced Multiple-Bit Upset

Outline

Alan D. Tipton1, Jonathan A. Pellish1,

Patrick R. Fleming1, Ronald D. Schrimpf1,2,

Robert A. Reed2, Robert A. Weller1,2,

Marcus H. Mendenhall3

- Vanderbilt University, Department of Electrical Engineering and Computer Science, Nashville,TN
- Vanderbilt University, Institute for Space and Defense Electronics, Nashville, TN
- Vanderbilt University, W. M. Keck Free Electron Laser Center, Nashville, TN

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

UpdateOutline

- Background
- Multiple-bit upset (MBU)
- Neutron-induced MBU
- Modeling
- Monte-Carlo Radiative Energy Deposition (MRED)
- Results
- Single-bit
- Multiple-bit
- Conclusion
- Future work

Outline

- Background
- Multiple-bit upset (MBU)
- Neutron-induced MBU
- Modeling
- Monte-Carlo Radiative Energy Deposition (MRED)
- Results
- Single-bit
- Multiple-bit
- Conclusion
- Future work

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

Nucleon-Induced MBU

Maiz et al.

Tosaka et al.

Kawakami et al.

Hubert et al.

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

Neutrons induce nuclear reactions

Incident Neutron

- Neutron-induced nuclear reactions
- Secondary products are ionizing particles that induce soft errors

Nuclear Reaction

Heavy-Ion

Sensitive

Nodes

Outline

- Background
- Multiple-bit upset (MBU)
- Neutron-induced MBU
- Modeling
- Monte-Carlo Radiative Energy Deposition (MRED)
- Results
- Single-bit
- Multiple-bit
- Conclusion
- Future work

- 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)

Sensitive

Node

Metallization

Neutron

Spectrum

TCAD

MRED

ED(E)

M(E)

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

Copper lines

Tungsten vias

Single Cell

Silicon bulk

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.

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

n+Si

C+3n+2p++3

- Background
- Multiple-bit upset (MBU)
- Neutron-induced MBU
- Modeling
- Monte-Carlo Radiative Energy Deposition (MRED)
- Results
- Single-bit
- Multiple-bit
- Conclusion
- Future work

Energy deposition cross section

- ED(E)Cross section to deposit at least E in the sensitive volume
- Relationship to SEU cross section

SEU = ED (Qcrit)

Charge Generated (fC)

Energy Deposited (MeV)

0°

90°

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

Charge Generated (fC)

Energy Deposited (MeV)

0°

90°

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

Charge Generated (fC)

Energy Deposited (MeV)

Multiple bit multiplicity

- MBU characterized for bit multiplicity
- Probability of an event decreases with increasing multiplicity

#Events(multiplicity)

fluence

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

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

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

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