MURI 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 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

MURI 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 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 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, Nucleon-Induced MBU Maiz et al. Tosaka et al. Kawakami et al. Hubert et al.

MURI 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

MURI 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 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 Sensitive Node  ED (E) Metallization  M (E) TCAD Neutron Spectrum

MURI 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

MURI 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.

MURI 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

MURI 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 Energy deposition cross section  ED (E)  Cross section to deposit at least E in the sensitive volume Relationship to SEU cross section  SEU =  ED (Q crit ) Energy Deposited (MeV) Charge Generated (fC)

MURI 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 Energy Deposited (MeV) Charge Generated (fC) 0° 45° 90°

MURI Frontside vs backside Backside shows increased cross section

MURI 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 Energy Deposited (MeV) Charge Generated (fC) 0° 45° 90°

MURI Multiple bit multiplicity MBU characterized for bit multiplicity Probability of an event decreases with increasing multiplicity #Events(multiplicity) fluence

MURI 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 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 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