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SEE Scaling Effects

SEE Scaling Effects. Lloyd Massengill 10 May 2005. Hierarchical Multi-Scale Analysis of Radiation Effects. Materials. Device Structure. IC Design. Energy Deposition. Defect Models. Circuit Response. Device Simulation. Scaling and SEUs.

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SEE Scaling Effects

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  1. SEE Scaling Effects Lloyd Massengill 10 May 2005

  2. Hierarchical Multi-Scale Analysis of Radiation Effects Materials Device Structure IC Design Energy Deposition Defect Models Circuit Response Device Simulation 10 May 2005

  3. Scaling and SEUs “Unconventional” SEE Mechanisms in Technology Nodes Below 100nm: • Charge Sharing • Distributed effects • Secondary (nuclear) Reactions • Probabilistic effects • Track Size as Large as the Critical Region • Spatial effects • Circuit Speed on the order of Collection Dynamics • Temporal effects 10 May 2005

  4. Scaling and SEUs “Unconventional” SEE Mechanisms in Technology Nodes Below 100nm: • Charge Sharing • Distributed effects • Secondary (nuclear) Reactions • Probabilistic effects • Track Size as Large as the Critical Region • Spatial effects • Circuit Speed on the order of Collection Dynamics • Temporal effects 10 May 2005

  5. Charge Sharing * NFETs PFETs Issue: At the 250nm CMOS technology node, we have observed two “unusual” effects • Heavy Ion – Very low LETth • Laser (2) – N-Well Edge * McMorrow et al, ”Single-Event Upset in Flip-Chip SRAM Induced by Through-Wafer, Two-Photon Absorption”, accepted to the 2005 NSRECWarren et al., “The Contribution of Nuclear Reactions to Single Event Upset Cross-Section Measurements in a High-Density SEU Hardened SRAM Technology”, accepted to the 2005 NSREC 10 May 2005

  6. Charge SharingBackground * H L Distributed-storage hardened SRAM cell: • “Single Node” events cannot produce an upset • Charge collection required at nodes on both legs • Event sequence • Sufficient charge must be collected on one leg to float the opposite leg • The floating leg must then collected enough charge to lose its state * Warren et al., “The Contribution of Nuclear Reactions to Single Event Upset Cross-Section Measurements in a High-Density SEU Hardened SRAM Technology”, accepted to the 2005 NSREC 10 May 2005

  7. Charge SharingSimulations * TCAD SPICE • Mixed-mode simulations (3-D TCAD + compact model) useful for efficiency • We constructed calibrated base structure for SEE mapping • VAMPIRE simulations: 4G Opteron nodes550,000 elements, 1.5 wks per * Olson et al, “Simultaneous SE Charge Sharing and Parasitic Bipolar Conduction in a Highly-Scaled SRAM Design,“ accepted to NSREC 2005 10 May 2005

  8. Charge SharingPreliminary Findings * H L • Functionally disjoint, but physically adjacent nodes share charge • In addition, parasitic conduction affects PFET of opposite rail M7 M2 M0 M8 M9 M4 M10 M5 * Olson et al, “Enhanced Single-Event Charge Collection in Submicron CMOS Due to a Diffusion-Triggered Parasitic LPNP” presented at HEART 05 10 May 2005

  9. Scaling and SEUs “Unconventional” SEE Mechanisms in Technology Nodes Below 100nm: • Charge Sharing • Distributed effects • Secondary (nuclear) Reactions • Probabilistic effects • Track Size as Large as the Critical Region • Spatial effects • Circuit Speed on the order of Collection Dynamics • Temporal effects 10 May 2005

  10. Secondary (Nuclear) Effects Issue: • Unable to explain upsets at very low LET in TCAD • Upset cross section too small to be intra-cell variation TCAD Prediction TCAD with average LET ion does not explain low LET upsets Approximate Ion Track Area (intra-cell Limit) Ultra Low s (follow-on at BNL) 10 May 2005

  11. Secondary (Nuclear) EffectsHypotheses • Nuclear reaction events can increase the effective LET to +/- 8x the incident LET for this simulation • In scaled technologies, the low probability of occurrence offset by: - high number of sensitive volumes (4 Mbit SRAM) - elimination of lower-LET sensitivity via hardening 523 MeV Neon LET = 1.79 MeV/mg/cm2 10 May 2005

  12. Secondary (Nuclear) EffectsPreliminary Analysis * W MRED used for preliminary investigation of potential event sources: • Conceptually simple relative energy deposition experiment • 1x108 Monte-Carlo type simulations • Reactions in the interconnect materials result in charge deposition from secondary species in the sensitive volume Oxide Only Oxide and Metallization * Warren et al., “The Contribution of Nuclear Reactions to Single Event Upset Cross-Section Measurements in a High-Density SEU Hardened SRAM Technology” accepted to the 2005 NSREC 10 May 2005

  13. Secondary (Nuclear) EffectsPreliminary MRED Results *Nuclear events only (in 1x108 simulations) Primary LET High Energy Events • Nuclear Reactions can produce products greater than 8x in energy deposition than the primary LET • Effect is exacerbated with inter-connect materials (tungsten, aluminum, etc…) 10 May 2005

  14. Secondary (Nuclear) EffectsOn-Going Work • Integration of multiple tools • Layout • TCAD modules • MRED (nuclear) • Accurate spatial relationship between sensitive regions and materials • Interconnect material affects the probability of extreme value events • Events must occur near the sensitive region to upset the cell • A step closer to developing a predictive tool 10 May 2005

  15. Scaling and SEUs “Unconventional” SEE Mechanisms in Technology Nodes Below 100nm: • Charge Sharing • Distributed effects • Secondary (nuclear) Reactions • Probabilistic effects • Track Size as Large as the Critical Region • Spatial effects • Circuit Speed on the order of Collection Dynamics • Temporal effects 10 May 2005

  16. Track Size Issue: • Device dimensions becoming smaller than • Commonly assumed radial dimensions for SE charge generation tracks • Minority carrier diffusion lengths (even in Drain/Source regions) • Device topology has implications for charge deposition (1) (2) M. L. Alles, et. al. , “Considerations for Single Event Effects in Non-Planar Multi-Gate SOI FETs”, submitted for presentation at the 2005 IEEE International SOI Conference. R. Chau et. al., “Advanced Depleted-Substrate Transistors: Single-Gate, Double-Gate, Tri-Gate”, 2002 International Conference on Solid State Devices and Materials (SSDM 2002), Nagoya, Japan. 10 May 2005

  17. Track Size Hit to Channel Preliminary Simulations: • Simulation of an ion hit using 3D TCAD • (Alpha Particle, LET=2.4 MeV/mg-cm2) • Normal incidence • Three locations (Body, Drain, Source) • Response shows much longer time profile vs. direct collection; • Potential profile indicates bipolar action M. L. Alles, et. al. , “Considerations for Single Event Effects in Non-Planar Multi-Gate SOI FETs”, submitted for presentation at the 2005 IEEE International SOI Conference. Simulated Tri-gate device based on: J Choi et. al., IEDM Technical Digest, 647 (2004). 10 May 2005

  18. Track Size Preliminary Findings: • Hits to Drain (and Source) can lead to notable charge collection • Implication for sensitive area • Drain and source contribution found to depend on contact placement and size • Energy deposition process in such small devices unclear • Convention LET concept may break down • We will study this with detailed simulations (MRED) • Accurate TCAD modeling (FLOODS) M. L. Alles, et. al. , “Considerations for Single Event Effects in Non-Planar Multi-Gate SOI FETs”, submitted for presentation at the 2005 IEEE International SOI Conference. 10 May 2005

  19. Scaling and SEUs “Unconventional” SEE Mechanisms in Technology Nodes Below 100nm: • Charge Sharing • Distributed effects • Secondary (nuclear) Reactions • Probabilistic effects • Track Size as Large as the Critical Region • Spatial effects • Circuit Speed on the order of Collection Dynamics • Temporal effects 10 May 2005

  20. Circuit Speed Issue: • GHz circuitry have response dynamics on the same order as charge collection transient profiles • In these cases, SE transients are indistinguishable from legitimate signals • Some hardening techniques are ineffective • Dynamic modeling required • Detailed SE charge collection profiles are needed 10 May 2005

  21. Conclusions An understanding of SEE in emerging, scaled technologies (SiGe, ultra-small CMOS and 3-d SOI) constructed with novel materials systems (strained Si, alternative dielectrics, new metallizations) requires: • Improved physical models for ion interaction with materials other than Si • Detailed SE track structure models • Improved understanding of nuclear reaction effects • Improved device physics for mixed-mode modeling • Improved understanding of parasitic charge collection 10 May 2005

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