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Using MRED to Screen Multiple-Node Charge-Collection Mitigated SOI Layouts

IEEE Transactions on Nuclear Science

Black, Jeffrey B.; Dame, Jeff A.; Black, Dolores A.; Dodd, Paul E.; Shaneyfelt, Marty R.; Teifel, John T.; Salas, Joseph G.; Steinbach, Robert; Davis, Matthew; Reed, Robert A.; Weller, Robert A.; Trippe, James M.; Warren, Kevin M.; Tonigan, Andrew M.; Schrimpf, Ronald D.; Marquez, Richard S.

Silicon-on-insulator latch designs and layouts that are robust to multiple-node charge collection are introduced. A general Monte Carlo radiative energy deposition (MRED) approach is used to identify potential single-event susceptibilities associated with different layouts prior to fabrication. MRED is also applied to bound single-event testing responses of standard and dual interlocked cell latch designs. Heavy ion single-event testing results validate new latch designs and demonstrate bounds for standard latch layouts.

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Understanding the Implications of a LINAC's Microstructure on Devices and Photocurrent Models

IEEE Transactions on Nuclear Science

McLain, Michael L.; McDonald, Joseph K.; Hembree, Charles E.; Sheridan, Timothy J.; Weingartner, Thomas A.; Dodd, Paul E.; Shaneyfelt, Marty R.; Hartman, Elmer F.; Black, Dolores A.

The effect of a linear accelerator's (LINAC's) microstructure (i.e., train of narrow pulses) on devices and the associated transient photocurrent models are investigated. The data indicate that the photocurrent response of Si-based RF bipolar junction transistors and RF p-i-n diodes is considerably higher when taking into account the microstructure effects. Similarly, the response of diamond, SiO2, and GaAs photoconductive detectors (standard radiation diagnostics) is higher when taking into account the microstructure. This has obvious hardness assurance implications when assessing the transient response of devices because the measured photocurrent and dose rate levels could be underestimated if microstructure effects are not captured. Indeed, the rate the energy is deposited in a material during the microstructure peaks is much higher than the filtered rate which is traditionally measured. In addition, photocurrent models developed with filtered LINAC data may be inherently inaccurate if a device is able to respond to the microstructure.

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Upsets in Erased Floating Gate Cells with High-Energy Protons

IEEE Transactions on Nuclear Science

Gerardin, S.; Bagatin, M.; Paccagnella, A.; Visconti, A.; Bonanomi, M.; Calabrese, M.; Chiavarone, L.; Ferlet-Cavrois, V.; Schwank, J.R.; Shaneyfelt, Marty R.; Dodds, N.; Trinczek, M.; Blackmore, E.

We discuss upsets in erased floating gate cells, due to large threshold voltage shifts, using statistical distributions collected on a large number of memory cells. The spread in the neutral threshold voltage appears to be too low to quantitatively explain the experimental observations in terms of simple charge loss, at least in SLC devices. The possibility that memories exposed to high energy protons and heavy ions exhibit negative charge transfer between programmed and erased cells is investigated, although the analysis does not provide conclusive support to this hypothesis.

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Analysis of TID Process, Geometry, and Bias Condition Dependence in 14-nm FinFETs and Implications for RF and SRAM Performance

IEEE Transactions on Nuclear Science

King, M.P.; Wu, X.; Eller, M.; Samavedam, S.; Shaneyfelt, Marty R.; Silva, A.I.; Draper, Bruce L.; Rice, W.C.; Meisenheimer, Timothy L.; Felix, J.A.; Zhang, E.X.; Haeffner, T.D.; Ball, D.R.; Shetler, K.J.; Alles, M.L.; Kauppila, J.S.; Massengill, Lloyd W.

Total ionizing dose results are provided, showing the effects of different threshold adjust implant processes and irradiation bias conditions of 14-nm FinFETs. Minimal radiation-induced threshold voltage shift across a variety of transistor types is observed. Off-state leakage current of nMOSFET transistors exhibits a strong gate bias dependence, indicating electrostatic gate control of the sub-fin region and the corresponding parasitic conduction path are the largest concern for radiation hardness in FinFET technology. The high-Vth transistors exhibit the best irradiation performance across all bias conditions, showing a reasonably small change in off-state leakage current and Vth, while the low-Vth transistors exhibit a larger change in off-state leakage current. The "worst-case" bias condition during irradiation for both pull-down and pass-gate nMOSFETs in static random access memory is determined to be the on-state (Vgs = Vdd). We find the nMOSFET pull-down and pass-gate transistors of the SRAM bit-cell show less radiation-induced degradation due to transistor geometry and channel doping differences than the low-Vth transistor. Near-threshold operation is presented as a methodology for reducing radiation-induced increases in off-state device leakage current. In a 14-nm FinFET technology, the modeling indicates devices with high channel stop doping show the most robust response to TID allowing stable operation of ring oscillators and the SRAM bit-cell with minimal shift in critical operating characteristics.

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Outstanding Conference Paper Award: 2015 IEEE Nuclear and Space Radiation Effects Conference

IEEE Transactions on Nuclear Science

Dodds, Nathaniel A.; Martinez, Marino M.; Dodd, Paul E.; Shaneyfelt, Marty R.; Sexton, Frederick W.; Black, Jeffrey B.; Lee, David S.; Swanson, Scot E.; Bhuva, B.L.; Warren, K.W.; Reed, R.A.; Trippe, J.M.; Sierawski, B.D.; Weller, R.A.; Mahatme, N.M.; Gaspard, N.G.; Assis, T.A.; Austin, R.A.; Weeden-Wright, S.L.; Massengill, L.M.; Swift, G.S.; Wirthlin, M.W.; Cannon, M.C.; Liu, R.L.; Chen, L.C.; Kelly, A.K.; Marshall, P.W.; Trinczek, M.C.; Blackmore, E.W.; Wen, S.-J.W.; Wong, R.W.; Narasimham, B.N.; Pellish, J.A.; Puchner, H.P.

This conference presents the recipients of the Outstanding Conference Paper Award from the 2015 IEEE Nuclear and Space Radiation Effects Conference.

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The Contribution of Low-Energy Protons to the Total On-Orbit SEU Rate

IEEE Transactions on Nuclear Science

Dodds, N.A.; Martinez, Marino M.; Dodd, Paul E.; Shaneyfelt, Marty R.; Sexton, Frederick W.; Black, J.D.; Lee, David S.; Swanson, Scot E.; Bhuva, B.L.; Warren, K.M.; Reed, R.A.; Trippe, J.; Sierawski, B.D.; Weller, R.A.; Mahatme, N.; Gaspard, N.J.; Assis, T.; Austin, R.; Weeden-Wright, S.L.; Massengill, L.W.; Swift, G.; Wirthlin, M.; Cannon, M.; Liu, R.; Chen, L.; Kelly, A.T.; Marshall, P.W.; Trinczek, M.; Blackmore, E.W.; Wen, S.J.; Wong, R.; Narasimham, B.; Pellish, J.A.; Puchner, H.

Low-and high-energy proton experimental data and error rate predictions are presented for many bulk Si and SOI circuits from the 20-90 nm technology nodes to quantify how much low-energy protons (LEPs) can contribute to the total on-orbit single-event upset (SEU) rate. Every effort was made to predict LEP error rates that are conservatively high; even secondary protons generated in the spacecraft shielding have been included in the analysis. Across all the environments and circuits investigated, and when operating within 10% of the nominal operating voltage, LEPs were found to increase the total SEU rate to up to 4.3 times as high as it would have been in the absence of LEPs. Therefore, the best approach to account for LEP effects may be to calculate the total error rate from high-energy protons and heavy ions, and then multiply it by a safety margin of 5. If that error rate can be tolerated then our findings suggest that it is justified to waive LEP tests in certain situations. Trends were observed in the LEP angular responses of the circuits tested. Grazing angles were the worst case for the SOI circuits, whereas the worst-case angle was at or near normal incidence for the bulk circuits.

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New Insights Gained on Mechanisms of Low-Energy Proton-Induced SEUs by Minimizing Energy Straggle

IEEE Transactions on Nuclear Science

Dodds, N.A.; Dodd, Paul E.; Shaneyfelt, Marty R.; Sexton, Frederick W.; Martinez, Marino M.; Black, J.D.; Marshall, P.W.; Reed, R.A.; McCurdy, M.W.; Weller, R.A.; Pellish, J.A.; Rodbell, K.P.; Gordon, M.S.

We present low-energy proton single-event upset (SEU) data on a 65 nm SOI SRAM whose substrate has been completely removed. Since the protons only had to penetrate a very thin buried oxide layer, these measurements were affected by far less energy loss, energy straggle, flux attrition, and angular scattering than previous datasets. The minimization of these common sources of experimental interference allows more direct interpretation of the data and deeper insight into SEU mechanisms. The results show a strong angular dependence, demonstrate that energy straggle, flux attrition, and angular scattering affect the measured SEU cross sections, and prove that proton direct ionization is the dominant mechanism for low-energy proton-induced SEUs in these circuits.

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New insights gained on mechanisms of low-energy proton-induced SEUs by minimizing energy straggle

IEEE Transactions on Nuclear Science

Dodds, Nathaniel A.; Dodd, Paul E.; Shaneyfelt, Marty R.; Sexton, Frederick W.; Martinez, Marino M.; Black, Jeffrey B.; Marshall, P.W.; Reed, R.A.; McCurdy, M.M.; Weller, R.A.; Pellish, J.A.; Rodbell, K.P.; Gordon, M.G.

In this study, we present low-energy proton single-event upset (SEU) data on a 65 nm SOI SRAM whose substrate has been completely removed. Since the protons only had to penetrate a very thin buried oxide layer, these measurements were affected by far less energy loss, energy straggle, flux attrition, and angular scattering than previous datasets. The minimization of these common sources of experimental interference allows more direct interpretation of the data and deeper insight into SEU mechanisms. The results show a strong angular dependence, demonstrate that energy straggle, flux attrition, and angular scattering affect the measured SEU cross sections, and prove that proton direct ionization is the dominant mechanism for low-energy proton-induced SEUs in these circuits.

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The contribution of low-energy protons to the total on-orbit SEU rate

IEEE Transactions on Nuclear Science

Dodds, Nathaniel A.; Martinez, Marino M.; Dodd, Paul E.; Shaneyfelt, Marty R.; Sexton, Frederick W.; Black, Jeffrey B.; Lee, David S.; Swanson, Scot E.; Bhuva, B.L.; Warren, K.W.; Reed, R.A.; Trippe, J.M.; Sierawski, B.D.; Weller, R.A.; Mahatme, N.M.; Gaspard, N.G.; Assis, T.A.; Austin, R.A.; Massengill, L.M.; Swift, G.S.; Wirthlin, M.W.; Cannon, M.C.; Liu, R.L.; Chen, L.C.; Kelly, A.K.; Marshall, P.W.; Trinczek, M.C.; Blackmore, E.W.; Wen, S.-J.W.; Wong, R.W.; Narasimham, B.N.; Pellish, J.A.; Puchner, H.P.

Low- and high-energy proton experimental data and error rate predictions are presented for many bulk Si and SOI circuits from the 20-90 nm technology nodes to quantify how much low-energy protons (LEPs) can contribute to the total on-orbit single-event upset (SEU) rate. Every effort was made to predict LEP error rates that are conservatively high; even secondary protons generated in the spacecraft shielding have been included in the analysis. Across all the environments and circuits investigated, and when operating within 10% of the nominal operating voltage, LEPs were found to increase the total SEU rate to up to 4.3 times as high as it would have been in the absence of LEPs. Therefore, the best approach to account for LEP effects may be to calculate the total error rate from high-energy protons and heavy ions, and then multiply it by a safety margin of 5. If that error rate can be tolerated then our findings suggest that it is justified to waive LEP tests in certain situations. Trends were observed in the LEP angular responses of the circuits tested. As a result, grazing angles were the worst case for the SOI circuits, whereas the worst-case angle was at or near normal incidence for the bulk circuits.

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The contribution of low-energy protons to the total on-orbit SEU rate

Dodds, Nathaniel A.; Martinez, Marino M.; Dodd, Paul E.; Shaneyfelt, Marty R.; Sexton, Frederick W.; Black, Jeffrey B.; Lee, David S.; Swanson, Scot E.; Bhuva, B.L.; Warren, K.W.; Reed, R.A.; Trippe, J.M.; Sierawski, B.D.; Weller, R.A.; Mahatme, N.M.; Gaspard, N.G.; Assis, T.A.; Austin, R.A.; Massengill, L.M.; Swift, G.S.; Wirthlin, M.W.; Cannon, M.C.; Liu, R.L.; Chen, L.C.; Kelly, A.K.; Marshall, P.W.; Trinczek, M.C.; Blackmore, E.W.; Wen, S.-J.W.; Wong, R.W.; Narasimham, B.N.; Pellish, J.A.; Puchner, H.P.

Abstract not provided.

Outstanding conference paper award 2014 IEEE nuclear and space radiation effects conference

IEEE Transactions on Nuclear Science

Dodds, Nathaniel A.; Dodds, Nathaniel A.; Schwank, James R.; Schwank, James R.; Shaneyfelt, Marty R.; Shaneyfelt, Marty R.; Dodd, Paul E.; Dodd, Paul E.; Doyle, Barney L.; Doyle, Barney L.; Trinczek, M.C.; Trinczek, M.C.; Blackmore, E.W.; Blackmore, E.W.; Rodbell, K.P.; Rodbell, K.P.; Reed, R.A.; Reed, R.A.; Pellish, J.A.; Pellish, J.A.; LaBel, K.A.; LaBel, K.A.; Marshall, P.W.; Marshall, P.W.; Swanson, Scot E.; Swanson, Scot E.; Vizkelethy, Gyorgy V.; Vizkelethy, Gyorgy V.; Van Deusen, Stuart B.; Van Deusen, Stuart B.; Sexton, Frederick W.; Sexton, Frederick W.; Martinez, Marino M.; Martinez, Marino M.

The recipients of the 2014 NSREC Outstanding Conference Paper Award are Nathaniel A. Dodds, James R. Schwank, Marty R. Shaneyfelt, Paul E. Dodd, Barney L. Doyle, Michael Trinczek, Ewart W. Blackmore, Kenneth P. Rodbell, Michael S. Gordon, Robert A. Reed, Jonathan A. Pellish, Kenneth A. LaBel, Paul W. Marshall, Scot E. Swanson, Gyorgy Vizkelethy, Stuart Van Deusen, Frederick W. Sexton, and M. John Martinez, for their paper entitled "Hardness Assurance for Proton Direct Ionization-Induced SEEs Using a High-Energy Proton Beam." For older CMOS technologies, protons could only cause single-event effects (SEEs) through nuclear interactions. Numerous recent studies on 90 nm and newer CMOS technologies have shown that protons can also cause SEEs through direct ionization. Furthermore, this paper develops and demonstrates an accurate and practical method for predicting the error rate caused by proton direct ionization (PDI).

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Hardness assurance for proton direct ionization-induced SEEs using a high-energy proton beam

IEEE Transactions on Nuclear Science

Dodds, N.A.; Schwank, James R.; Shaneyfelt, Marty R.; Dodd, Paul E.; Doyle, Barney L.; Trinczek, M.; Blackmore, E.W.; Rodbell, K.P.; Gordon, M.S.; Reed, R.A.; Pellish, J.A.; LaBel, K.A.; Marshall, P.W.; Swanson, Scot E.; Vizkelethy, Gyorgy V.; Van Deusen, Stuart B.; Sexton, Frederick W.; Martinez, Marino M.

The low-energy proton energy spectra of all shielded space environments have the same shape. This shape is easily reproduced in the laboratory by degrading a high-energy proton beam, producing a high-fidelity test environment. We use this test environment to dramatically simplify rate prediction for proton direct ionization effects, allowing the work to be done at high-energy proton facilities, on encapsulated parts, without knowledge of the IC design, and with little or no computer simulations required. Proton direct ionization (PDI) is predicted to significantly contribute to the total error rate under the conditions investigated. Scaling effects are discussed using data from 65-nm, 45-nm, and 32-nm SOI SRAMs. These data also show that grazing-angle protons will dominate the PDI-induced error rate due to their higher effective LET, so PDI hardness assurance methods must account for angular effects to be conservative. We show that this angular dependence can be exploited to quickly assess whether an IC is susceptible to PDI.

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Mapping of radiation-induced resistance changes and multiple conduction channels in TaOx memristors

IEEE Transactions on Nuclear Science

Hughart, David R.; Pacheco, Jose L.; Lohn, Andrew L.; Mickel, Patrick R.; Bielejec, Edward S.; Vizkelethy, Gyorgy V.; Doyle, Barney L.; Wolfley, Steven L.; Dodd, Paul E.; Shaneyfelt, Marty R.; McLain, Michael L.; Marinella, Matthew J.

The locations of conductive regions in TaOx memristors are spatially mapped using a microbeam and Nanoimplanter by rastering an ion beam across each device while monitoring its resistance. Microbeam irradiation with 800 keV Si ions revealed multiple sensitive regions along the edges of the bottom electrode. The rest of the active device area was found to be insensitive to the ion beam. Nanoimplanter irradiation with 200 keV Si ions demonstrated the ability to more accurately map the size of a sensitive area with a beam spot size of 40 nm by 40 nm. Isolated single spot sensitive regions and a larger sensitive region that extends approximately 300 nm were observed.

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SEGR in SiO${}_2$ –Si$_3$ N$_4$ Stacks

IEEE Transactions on Nuclear Science

Schwank, James R.; Shaneyfelt, Marty R.

This work presents experimental SEGR data for MOS-devices, where the gate dielectrics are are made of stacked SiO2–Si3N4 structures. Also a semi-empirical model for predicting the critical gate voltage in these structures under heavy-ion exposure is proposed. Then statistical interrelationship between SEGR cross-section data and simulated energy deposition probabilities in thin dielectric layers is discussed.

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SOI substrate removal for SEE characterization: Techniques and applications

IEEE Transactions on Nuclear Science

Shaneyfelt, Marty R.; Schwank, James R.; Dodd, Paul E.; Stevens, Jeffrey S.; Vizkelethy, Gyorgy; Swanson, Scot E.; Dalton, Scott M.

Techniques for removing the back substrate of SOI devices are described for both packaged devices and devices at the die level. The use of these techniques for microbeam, heavy-ion, and laser testing are illustrated. © 2012 IEEE.

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Hardness assurance testing for proton direct ionization effects

Proceedings of the European Conference on Radiation and its Effects on Components and Systems, RADECS

Schwank, James R.; Shaneyfelt, Marty R.; Ferlet-Cavrois, Véronique; Dodd, Paul E.; Blackmore, Ewart W.; Pellish, Jonathan A.; Rodbell, Kenneth P.; Heidel, David F.; Marshall, Paul W.; LaBel, Kenneth A.; Gouker, Pascale M.; Tam, Nelson; Wong, Richard; Wen, Shi J.; Reed, Robert A.; Dalton, Scott M.; Swanson, Scot E.

The potential for using the degraded beam of high-energy proton radiation sources for proton hardness assurance testing for ICs that are sensitive to proton direct ionization effects are explored. SRAMs were irradiated using high energy proton radiation sources (∼67-70 MeV). The proton energy was degraded using plastic or Al degraders. Peaks in the SEU cross section due to direct ionization were observed. To best observe proton direct ionization effects, one needs to maximize the number of protons in the energy spectrum below the proton energy SEU threshold. SRIM simulations show that there is a tradeoff between increasing the fraction of protons in the energy spectrum with low energies by decreasing the peak energy and the reduction in the total number of protons as protons are stopped in the device as the proton energy is decreased. Two possible methods for increasing the number of low energy protons is to decrease the primary proton energy to reduce the amount of energy straggle and to place the degrader close to the DUT to minimize angular dispersion. These results suggest that high-energy proton radiation sources may be useful for identifying devices sensitive to proton direct ionization. © 2011 IEEE.

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Dosimetry experiments at the MEDUSA Facility (Little Mountain)

Harper-Slaboszewicz, V.H.; Hartman, Elmer F.; Shaneyfelt, Marty R.; Schwank, James R.; Sheridan, Timothy J.

A series of experiments on the MEDUSA linear accelerator radiation test facility were performed to evaluate the difference in dose measured using different methods. Significant differences in dosimeter-measured radiation dose were observed for the different dosimeter types for the same radiation environments, and the results are compared and discussed in this report.

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Effects of moisture on radiation-induced degradation in CMOS SOI transistors

IEEE Transactions on Nuclear Science

Shaneyfelt, Marty R.; Schwank, James R.; Dodd, Paul E.; Hill, Thomas A.; Dalton, Scott M.; Swanson, Scot E.

The effects of moisture on radiation-induced charge buildup in the oxides of a 0.35 μSOI technology are explored. Data show no observable effects of moisture-related aging on radiation hardness. These results are in contrast to those of previous work performed on bulk MOS technologies fabricated in the 1980s. The cause of these differences do not appear to be due to differences in final chip passivation layers. Instead, other processing variables (e.g., thicker overlayers) may account for these differences. In any case, the SOI technology results indicate that not all advanced technologies exposed to moisture are necessarily susceptible to enhanced radiation-induced degradation. © 2010 IEEE.

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Hardness assurance test guideline for qualifying devices for use in proton environments

IEEE Transactions on Nuclear Science

Schwank, James R.; Shaneyfelt, Marty R.; Dodd, Paul E.; Felix, James A.; Baggio, J.; Ferlet-Cavrois, V.; Paillet, P.; Label, K.A.; Pease, R.L.; Simons, M.; Cohn, L.M.

Proton-induced singl -event effects hardness assurance guidelines are developed to address issues raised by recent test results in advanced IC technologies for use in space environments. Specifically, guidelines are developed that address the effects of proton energy and angle of incidence on single-event latchup and the effects of total dose on single-event upset. The guidelines address both single-event upset (SEU), single-event latchup (SEL), and combined SEU and total ionizing dose (TID) effects. © 2006 IEEE.

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Total ionizing dose effects in NOR and NAND flash memories

IEEE Transactions on Nuclear Science

Cellere, Giorgio; Paccagnella, Alessandro; Visconti, Angelo; Bonanomi, Mauro; Beltrami, S.; Schwank, James R.; Shaneyfelt, Marty R.; Paillet, Philippe

We irradiated floating gate (FG) memories with NOR and NAND architecture by using different TID sources, including 2 MeV, 98 MeV, and 105 MeV protons, X-rays, and γ-rays. Two classes of phenomena are responsible for charge loss from programmed FGs: the first is charge generation, recombination, and transport in the dielectrics, while the second is the emission of electrons above the oxide band. Charge loss from programmed FGs irradiated with protons of different energy closely tracks results from γ-rays, whereas the use of X-rays results in dose enhancement effects. © 2007 IEEE.

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Effects of total dose irradiation on single-event upset hardness

IEEE Transactions on Nuclear Science

Schwank, James R.; Shaneyfelt, Marty R.; Felix, James A.; Dodd, Paul E.; Baggio, J.; Ferlet-Cavrois, V.; Paillet, P.; Hash, Gerald L.; Flores, Richard S.; Massengill, L.W.; Blackmore, E.

The effect of total dose on SEU hardness is investigated as a function of temperature and power supply voltage to determine worst-case hardness assurance test conditions for space environments. SRAMs from six different vendors were characterized for single-event upset (SEU) hardness at proton energies from 20 to 500 MeV and at temperatures of 25 and 80°C after total dose irradiating the SRAMs with either protons, Co-60 gamma rays, or low-energy x-rays. It is shown that total dose irradiation and the memory pattern written to the memory array during total dose irradiation and SEU characterization can substantially affect SEU hardness for some SRAMs. For one SRAM, the memory pattern made more than two orders of magnitude difference in SEU cross section at the highest total dose level examined. For all SRAMs investigated, the memory pattern that led to the largest increase in SEU cross section was the same memory pattern that led to the maximum increase in total-dose induced power supply leakage current. In addition, it is shown that increasing the temperature during SEU characterization can also increase the effect of total dose on SEU hardness. As a result, worst-case SEU hardness assurance test conditions are the maximum total dose and temperature of the system environment, and the minimum operating voltage of the SRAM. Possible screens for determining whether or not the SEU cross section of an SRAM will vary with total dose, based on the magnitude of the increase in power supply leakage current with total dose or the variation in SEU cross section with power supply voltage, have been suggested. In contrast to previous works, our results using selective area x-ray irradiations show that the source of the effect of total dose on SEU hardness is radiation-induced leakage currents in the memory cells. The increase in SEU cross section with total dose appears to be consistent with radiation-induced currents originating in the memory cells affecting the output bias levels of bias level shift circuitry used to control the voltage levels to the memory cells and/or due to the lowering of the noise margin of individual memory cells caused by radiation-induced leakage currents. © 2006 IEEE.

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Elimination of enhanced low-dose-rate sensitivity in linear bipolar devices using silicon-carbide passivation

IEEE Transactions on Nuclear Science

Shaneyfelt, Marty R.; Maher, Michael C.; Camilletti, Robert C.; Schwank, James R.; Pease, Ronald L.; Russell, Brian A.; Dodd, Paul E.

The type of final chip passivation layer used to fabricate linear bipolar circuits can have a major impact on the total dose hardness of some circuits. It is demonstrated that National Semiconductor Corporation linear bipolar devices fabricated with only an amorphous silicon carbide passivation layer do not exhibit enhanced low-dose-rate sensitivity (ELDRS), while devices from the same production lot fabricated with other types of passivation layers are ELDRS sensitive. SiC passivation possesses mechanical, electrical and chemical properties that make it compatible with linear device fabrication processes. These properties of SiC passivation layers, combined with the excellent radiation response of devices passivated with SiC, make SiC passivation layers a very attractive choice for devices packaged in either ceramic or plastic-encapsulated packages for use in space environments. © 2006 IEEE.

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Effects of particle energy on proton-induced single-event latchup

IEEE Transactions on Nuclear Science

Schwank, James R.; Shaneyfelt, Marty R.; Baggio, J.; Dodd, Paul E.; Felix, James A.; Ferlet-Cavrois, V.; Paillet, P.; Lambert, D.; Sexton, Frederick W.; Hash, Gerald L.; Blackmore, E.

The effect of proton energy on single-event latchup (SEL) in present-day SRAMs is investigated over a wide range of proton energies and temperature. SRAMs from five different vendors were irradiated at proton energies from 20 to 500 MeV and at temperatures of 25° and 85°C. For the SRAMs and radiation conditions examined in this work, proton energy SEL thresholds varied from as low as 20 MeV to as high as 490 MeV. To gain insight into the observed effects, the heavy-ion SEL linear energy transfer (LET) thresholds of the SRAMs were measured and compared to high-energy transport calculations of proton interactions with different materials. For some SRAMs that showed proton-induced SEL, the heavy-ion SEL threshold LET was as high as 25 MeV-cm 2/mg. Proton interactions with Si cannot generate nuclear recoils with LETs this large. Our nuclear scattering calculations suggest that the nuclear recoils are generated by proton interactions with tungsten. Tungsten plugs are commonly used in most high-density ICs fabricated today, including SRAMs. These results demonstrate that for system applications where latchups cannot be tolerated, SEL hardness assurance testing should be performed at a proton energy at least as high as the highest proton energy present in the system environment. Moreover, the best procedure to ensure that ICs will be latchup free in proton environments may be to use a heavy-ion source with LETs ≥40 MeV-cm 2/mg. © 2005 IEEE.

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Radiation-induced off-state leakage current in commercial power MOSFETs

Proposed for publication in the IEEE Transactions on Nuclear Science.

Felix, James A.; Shaneyfelt, Marty R.; Dodd, Paul E.; Draper, Bruce L.; Schwank, James R.; Dalton, Scott D.

The total dose hardness of several commercial power MOSFET technologies is examined. After exposure to 20 krad(SiO{sub 2}) most of the n- and p-channel devices examined in this work show substantial (2 to 6 orders of magnitude) increases in off-state leakage current. For the n-channel devices, the increase in radiation-induced leakage current follows standard behavior for moderately thick gate oxides, i.e., the increase in leakage current is dominated by large negative threshold voltage shifts, which cause the transistor to be partially on even when no bias is applied to the gate electrode. N-channel devices biased during irradiation show a significantly larger leakage current increase than grounded devices. The increase in leakage current for the p-channel devices, however, was unexpected. For the p-channel devices, it is shown using electrical characterization and simulation that the radiation-induced leakage current increase is related to an increase in the reverse bias leakage characteristics of the gated diode which is formed by the drain epitaxial layer and the body. This mechanism does not significantly contribute to radiation-induced leakage current in typical p-channel MOS transistors. The p-channel leakage current increase is nearly identical for both biased and grounded irradiations and therefore has serious implications for long duration missions since even devices which are usually powered off could show significant degradation and potentially fail.

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Arsenic ion implant energy effects on CMOS gate oxide hardness

Proposed for publication in the IEEE Transactions on Nuclear Science.

Draper, Bruce L.; Shaneyfelt, Marty R.; Young, Ralph W.; Headley, Thomas J.; Dondero, Richard D.

Under conditions that were predicted as 'safe' by well-established TCAD packages, radiation hardness can still be significantly degraded by a few lucky arsenic ions reaching the gate oxide during self-aligned CMOS source/drain ion implantation. The most likely explanation is that both oxide traps and interface traps are created when ions penetrate and damage the gate oxide after channeling or traveling along polysilicon grain boundaries during the implantation process.

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Direct measurement of transient pulses induced by laser and heavy ion irradiation in deca-nanometer devices

Proposed for publication in the IEEE Transactions on Nuclear Science.

Schwank, James R.; Shaneyfelt, Marty R.

This paper investigates the transient response of 50-nm gate length fully and partially depleted SOI and bulk devices to pulsed laser and heavy ion microbeam irradiations. The measured transient signals on 50-nm fully depleted devices are very short, and the collected charge is small compared to older 0.25-{micro}m generation SOI and bulk devices. We analyze in detail the influence of the SOI architecture (fully or partially depleted) on the pulse duration and the amount of bipolar amplification. For bulk devices, the doping engineering is shown to have large effects on the duration of the transient signals and on the charge collection efficiency.

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Identification of radiation-induced parasitic leakage paths using light emission microscopy

IEEE Transactions on Nuclear Science

Shaneyfelt, Marty R.; Tangyunyong, Paiboon T.; Hill, Thomas A.; Soden, Jerry M.; Flores, Richard S.; Schwank, James R.; Dodd, Paul E.; Hash, Gerald L.

Eliminating radiation-induced parasitic leakage paths in integrated circuits (ICs) is key to improving their total dose hardness. Semiconductor manufacturers can use a combination of design and/or process techniques to eliminate known radiation-induced parasitic leakage paths. However, unknown or critical radiation-induced parasitic leakage may still exist on fully processed ICs and it is extremely difficult (if not impossible) to identify these leakage paths based on radiation induced parametric degradation. We show that light emission microscopy can be used to identify the location of radiation-induced parasitic leakage paths in ICs. This is illustrated by using light emission microscopy to find radiation-induced parasitic leakage paths in partially-depleted silicon on insulator static random-access memories (SRAMs). Once leakage paths were identified, modifications were made to the SRAM design to improve the total dose radiation hardness of the SRAMs. Light emission microscopy should prove to be an important tool for the development of future radiation hardened technologies and devices.

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Radiation effects microscopy for failure analysis of microelectronic devices

Doyle, Barney L.; Dodd, Paul E.; Shaneyfelt, Marty R.; Schwank, James R.

Microelectronic devices in satellites and spacecraft are exposed to high energy cosmic radiation. Furthermore, Earth-based electronics can be affected by terrestrial radiation. The radiation causes a variety of Single Event Effects (SEE) that can lead to failure of the devices. High energy heavy ion beams are being used to simulate both the cosmic and terrestrial radiation to study radiation effects and to ensure the reliability of electronic devices. Broad beam experiments can provide a measure of the radiation hardness of a device (SEE cross section) but they are unable to pinpoint the failing components in the circuit. A nuclear microbeam is an ideal tool to map SEE on a microscopic scale and find the circuit elements (transistors, capacitors, etc.) that are responsible for the failure of the device. In this paper a review of the latest radiation effects microscopy (REM) work at Sandia will be given. Different SEE mechanisms (Single Event Upset, Single Event Transient, etc.) and the methods to study them (Ion Beam Induced Charge (IBIC), Single Event Upset mapping, etc.) will be discussed. Several examples of using REM to study the basic effects of radiation in electronic devices and failure analysis of integrated circuits will be given.

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Generation of metastable electron traps in the near interfacial region of SOI buried oxides by ion implantation and their effect on device properties

Microelectronic Engineering

Schwank, James R.; Fleetwood, D.M.; Xiong, H.D.; Shaneyfelt, Marty R.; Draper, Bruce L.

Implanting the buried oxide of silicon-on-insulator technologies can create electron traps throughout the buried oxide that can compensate the buildup of radiation-induced positive charge. These can be used as an effective method for total-dose hardening buried oxides in SOI devices. In this work, we show that implanting buried oxides can also create thermally activated metastable electron traps near the top Si/SiO2 border. These metastable electron traps can produce significant bias instabilities in the back-gate transistor characteristics and lead to threshold voltage instabilities in fully-depleted devices. © 2004 Elsevier B.V. All rights reserved.

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Charge Collection by Capacitive Influence Through Isolation Oxides

IEEE Transactions on Nuclear Science

Ferlet-Cavrois, V.; Paillet, P.; Schwank, James R.; Vizkelethy, G.; Shaneyfelt, Marty R.; Baggio, J.; Torres, A.; Flament, O.

This paper analyzes the collected charge in heavy ion irradiated MOS structures. The charge generated in the substrate induces a displacement effect which strongly depends on the capacitor structure. Networks of capacitors are particularly sensitive to charge sharing effects. This has important implications for the reliability of SOI and DRAMs which use isolation oxides as a key elementary structure. The buried oxide of presentday and future SOI technologies is thick enough to avoid a significant collection from displacement effects. On the other hand, the retention capacitors of trench DRAMs are particularly sensitive to charge release in the substrate. Charge collection on retention capacitors participate to the MBU sensitivity of DRAM.

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Improved capabilities for proton and neutron irradiations at TRIUMF

Shaneyfelt, Marty R.; Dodd, Paul E.; Shaneyfelt, Marty R.

Improvements have been made at TRIUMF to permit higher proton intensities of up to 10{sup 10} cm{sup -2}s{sup -1} over the energy range 20-500 MeV. This improved capability enables the study of displacement damage effects that require higher fluence irradiations. In addition, a high energy neutron irradiation capability has been developed for terrestrial cosmic ray soft error rate (SER) characterization of integrated circuits. The neutron beam characteristics of this facility are similar to those currently available at the Los Alamos National Laboratory WNR test facility. SER data measured on several SRAMs using the TRIUMF neutron beam are in good agreement with the results obtained on the same devices using the WNR facility. The TRIUMF neutron beam also contains thermal neutrons that can be easily removed by a sheet of cadmium. The ability to choose whether thermal neutrons are present is a useful attribute not possible at the WNR.

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Mechanisms for radiation dose-rate sensitivity of bipolar transistors

Hjalmarson, Harold P.; Hjalmarson, Harold P.; Shaneyfelt, Marty R.; Schwank, James R.; Edwards, Arthur H.; Hembree, Charles E.; Mattsson, Thomas M.

Mechanisms for enhanced low-dose-rate sensitivity are described. In these mechanisms, bimolecular reactions dominate the kinetics at high dose rates thereby causing a sub-linear dependence on total dose, and this leads to a dose-rate dependence. These bimolecular mechanisms include electron-hole recombination, hydrogen recapture at hydrogen source sites, and hydrogen dimerization to form hydrogen molecules. The essence of each of these mechanisms is the dominance of the bimolecular reactions over the radiolysis reaction at high dose rates. However, at low dose rates, the radiolysis reaction dominates leading to a maximum effect of the radiation.

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Radiation-induced charge trapping in thin Al2O3/SiOxNy/Si(100) gate dielectric stacks

Proposed for publication in IEEE Transactions on Nuclear Science.

Felix, James A.; Shaneyfelt, Marty R.; Meisenheimer, Timothy L.; Schwank, James R.; Dodd, Paul E.

We examine the total-dose radiation response of capacitors and transistors with stacked Al{sub 2}O{sub 3} on oxynitride gate dielectrics with Al and poly-Si gates after irradiation with 10 keV X-rays. The midgap voltage shift increases monotonically with dose and depends strongly on both Al{sub 2}O{sub 3} and SiO{sub x}N{sub y} thickness. The thinnest dielectrics, of most interest to industry, are extremely hard to ionizing irradiation, exhibiting only {approx}50 mV of shift at a total dose of 10 Mrad(SiO{sub 2}) for the worst case bias condition. Oxygen anneals are found to improve the total dose radiation response by {approx}50% and induce a small amount of capacitance-voltage hysteresis. Al{sub 2}O{sub 3}/SiO{sub x}N{sub y} dielectrics which receive a {approx}1000 C dopant activation anneal trap {approx}12% more of the initial charge than films annealed at 550 C. Charge pumping measurements show that the interface trap density decreases with dose up to 500 krad(SiO{sub 2}). This surprising result is discussed with respect to hydrogen effects in alternative dielectric materials, and may be the result of radiation-induced hydrogen passivation of some of the near-interfacial defects in these gate dielectrics.

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Passivation layers for reduced total dose effects and ELDRS in linear bipolar devices

Proposed for publication in IEEE Transactions on Nuclear Science.

Shaneyfelt, Marty R.; Schwank, James R.; Dodd, Paul E.; Riewe, Leonard C.

It is shown that final chip passivation layers can have a significant impact on total dose hardness. A number of final chip passivation layers are evaluated to identify films that mitigate enhanced low-dose-rate sensitivity (ELDRS) in National Semiconductor Corporation's linear bipolar technologies. It is shown that devices fabricated with either a low temperature oxide or a tetraethyl ortho silicate passivation do not exhibit significant ELDRS effects up to 100 krad(SiO{sub 2}). Passivation studies on CMOS SRAMs suggest that it is unlikely that the passivation layers (or processing tools) are acting as a new source of hydrogen, which could drift or diffuse into the oxide and increase ELDRS sensitivity. Instead, it is possible that the passivation layers affect the mechanical stress in the oxide, which may affect oxide trap properties and possibly the release and mobility of hydrogen. Correlations between mechanical stress induced by the passivation layers and radiation degradation are discussed.

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Radiation effects in SOI technologies

IEEE Transactions on Nuclear Science

Schwank, James R.; Ferlet-Cavrois, V.; Shaneyfelt, Marty R.; Paillet, P.; Dodd, Paul E.

Silicon-on-insulator (SOI) technologies have been developed for radiation-hardened applications for many years and are rapidly becoming a main-stream commercial technology. The authors review the total dose, single-event effects, and dose rate hardness of SOI devices. The total dose response of SOI devices is more complex than for bulk-silicon devices due to the buried oxide. Radiation-induced trapped charge in the buried oxide can increase the leakage current of partially depleted transistors and decrease the threshold voltage and increase the leakage current of fully depleted transistors. Process techniques that reduce the net amount of radiation-induced positive charge trapped in the buried oxide and device design techniques that mitigate the effects of trapped charge in the buried oxide have been developed to harden SOI devices to bulk-silicon device levels. The sensitive volume for charge collection in SOI technologies is much smaller than for bulk-silicon devices potentially making SOI devices much harder to single-event upset (SEU). However, bipolar amplification caused by floating body effects can significantly reduce the SEU hardness of SOI devices. Body ties are used to reduce floating body effects and improve SEU hardness. SOI ICs are completely immune to classic four-layer p-n-p-n single-event latchup; however, floating body effects make SOI ICs susceptible to single-event snapback (single transistor latch). The sensitive volume for dose rate effects is typically two orders of magnitude lower for SOI devices than for bulk-silicon devices. By using body ties to reduce bipolar amplification, much higher dose rate upset levels can be achieved for SOI devices than for bulk-silicon devices.

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Long-term reliability degradation of ultrathin dielectric films due to heavy-ion irradiation

IEEE Transactions on Nuclear Science

Schwank, James R.; Shaneyfelt, Marty R.; Meisenheimer, Timothy L.; Dodd, Paul E.

High-energy ion-irradiated 3.3-nm oxynitride film and 2.2-nm SiO2-film MOS capacitors show premature breakdown during subsequent electrical stress. This degradation in breakdown increases with increasing ion linear energy transfer (LET), increasing ion fluence, and decreasing oxide thickness. We explain the reliability degradation due to high-energy ion-induced latent defects by a simple percolation model of conduction through SiO2 layers with irradiation and/or electrical stress-induced defects. Monitoring the gate-leakage current reveals the presence of latent defects in the dielectric films. Finally, our results may be significant to future single-event effects and single-event gate rupture tests for MOS devices and ICs with ultrathin gate oxides.

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Investigation of body-tie effects on ion beam induced charge collection in silicon-on-insulator FETs using the Sandia nuclear microprobe

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

Walsh, David S.; Dodd, Paul E.; Shaneyfelt, Marty R.; Schwank, James R.

Silicon-on-insulator (SOI) technology exhibits three main advantages over bulk silicon technology for use in radiation environments. (1) SOI devices are immune to latchup, (2) the volume of the sensitive region (body) and hence total charge collection per transient irradiation is much reduced in SOI devices and (3) the insulating layer blocks charge collection from the substrate (i.e., no funneling effect). This effectively raises the single event upset (SEU) threshold for the SOI device. However, despite their small active volume SOI devices are still vulnerable to single event effects (SEE). Inherent in the SOI transistor design is a parasitic npn bipolar junction transistor (BJT), where the source-body-drain acts as an emitter-base-collector BJT. An ion strike to a floating (not referenced to a specific potential) body creates a condition where the excess minority carriers in the drain-body cause the parasitic BJT to turn on and inject more charge into the drain than was deposited in the device by the ion. In extreme cases the floating body effect (FBE) can trigger a high-current state called single-event snapback (SES) where channel conduction is sustained indefinitely through regenerative electron-impact ionization near the drain junction. Tying the body to the source limits the emitter-base current and reduces the sensitivity of the device to single ion strikes. Unfortunately, the body-tie loses effectiveness with distance due to resistivity, and in regions far enough from the tie the BJT is still in effect. Using the Sandia nuclear microprobe we have created charge collection maps on Sandia CMOS6rs SOI FETs of varying channel widths. These devices have body ties at both ends of the channel region. Results clearly demonstrate that distance of the ion strike from the body tie has an inverse effect upon charge collection and SES sensitivity due to the resistivity of the channel. Experimental results compare well with DAVINCI simulations and electrically induced snapback thresholds. In addition, an intere sting saturation effect of SES versus the amount of injected charge is observed. © 2001 Elsevier Science B.V. All rights reserved.

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Origins of total-dose response variability in linear bipolar microcircuits

IEEE Transactions on Nuclear Science

Barnaby, H.J.; Cirba, C.R.; Schrimpf, R.D.; Fleetwood, D.M.; Pease, R.L.; Shaneyfelt, Marty R.; Turflinger, T.; Krieg, J.F.; Maher, M.C.

LM111 voltage comparators exhibit a wide range of total-dose-induced degradation. Simulations show this variability may be a natural consequence of the low base doping of the substrate PNP (SPNP) input transistors. Low base doping increases the SPNPs collector to base breakdown voltage, current gain, and densities. The build-up of oxide trapped charge (N OT) and interface traps (N IT) is shown to be a function of pre-irradiation bakes. Experimental data indicate that, despite its structural similarities to the LM111, irradiated input transistors of the LM124 operational amplifier do not exhibit the same sensitivity to variations in pre-irradiation thermal cycles. Further disparities in LM111 and LM124 responses may result from a difference in the oxide defect build-up in the two part types. Variations in processing, packaging, and circuit effects are suggested as potential explanations.

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Worst-case bias during total dose irradiation of SOI transistors

IEEE Transactions on Nuclear Science

Ferlet-Cavrois, V.; Colladant, T.; Paillet, P.; Leray, J.L.; Musseau, O.; Schwank, James R.; Shaneyfelt, Marty R.; Pelloie, J.L.; Du Port De Poncharra, J.

The worst case bias during total dose irradiation of partially depleted SOI transistors from two technologies is correlated to the device architecture. Experiments and simulations are used to analyze SOI back transistor threshold voltage shift and charge trapping in the buried oxide.

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Single-Event Upset and Snapback in Silicon-on-Insulator Devices and Integrated Circuits

IEEE Transactions on Nuclear Science

Dodd, Paul E.; Shaneyfelt, Marty R.; Walsh, David S.; Schwank, James R.; Hash, Gerald L.; Jones, Rhonda L.; Draper, Bruce L.; Winokur, Peter S.

The characteristics Of ion-induced charge collection and single-event upset are studied in SOI transistors and circuits with various body tie structures. Impact ionization effects including single-event snapback are shown to be very important. Focused ion microbeam experiments are used to find single-event snapback drain voltage thresholds in n-channel SOI transistors as a function of device width. Three-Dimensional device simulations are used to determine single-event upset and snapback thresholds in SOI SRAMS, and to study design tradeoffs for various body-tie structures. A window of vulnerability to single-event snapback is shown to exist below the single-event upset threshold. The presence of single-event snapback in commercial SOI SRAMS is confirmed through broadbeam ion testing, and implications for hardness assurance testing of SOI integrated circuits are discussed.

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Field Dependent Dopant Deactivation in Bipolar Devices at Elevated irradiation Temperatures

IEEE Transactions on Nuclear Science

Witczak, Steven C.; Shaneyfelt, Marty R.; Schwank, James R.; Winokur, Peter S.

Metal-oxide-silicon capacitors fabricated in a bi-polar process were examined for densities of oxide trapped charge, interface traps and deactivated substrate acceptors following high-dose-rate irradiation at 100 C. Acceptor neutralization near the Si surface occurs most efficiently for small irradiation biases in depletion. The bias dependence is consistent with compensation and passivation mechanisms involving the drift of H{sup +} ions in the oxide and Si layers and the availability of holes in the Si depletion region. Capacitor data from unbiased irradiations were used to simulate the impact of acceptor neutralization on the current gain of an npn bipolar transistor. Neutralized acceptors near the base surface enhance current gain degradation associated with radiation-induced oxide trapped charge and interface traps by increasing base recombination. The additional recombination results from the convergence of carrier concentrations in the base and increased sensitivity of the base to oxide trapped charge. The enhanced gain degradation is moderated by increased electron injection from the emitter. These results suggest that acceptor neutralization may enhance radiation-induced degradation of linear circuits at elevated temperatures.

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Correlation between Co-60 and x-ray exposures on radiation-induced charge buildup in silicon-on-insulator buried oxides

Schwank, James R.; Shaneyfelt, Marty R.; Jones, Rhonda L.; Draper, Bruce L.; Dodd, Paul E.; Witczak, Steven C.; Riewe, Leonard C.

Large differences in charge buildup in SOI buried oxides can result between x-ray and Co-60 irradiations. The effects of bias configuration and substrate type on charge buildup and hardness assurance issues are explored.

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LDRD Final Report - Investigations of the impact of the process integration of deposited magnetic films for magnetic memory technologies on radiation-hardened CMOS devices and circuits - LDRD Project (FY99)

Myers, David R.; Jessing, Jeffrey R.; Spahn, Olga B.; Shaneyfelt, Marty R.

This project represented a coordinated LLNL-SNL collaboration to investigate the feasibility of developing radiation-hardened magnetic non-volatile memories using giant magnetoresistance (GMR) materials. The intent of this limited-duration study was to investigate whether giant magnetoresistance (GMR) materials similar to those used for magnetic tunnel junctions (MTJs) were process compatible with functioning CMOS circuits. Sandia's work on this project demonstrated that deposition of GMR materials did not affect the operation nor the radiation hardness of Sandia's rad-hard CMOS technology, nor did the integration of GMR materials and exposure to ionizing radiation affect the magnetic properties of the GMR films. Thus, following deposition of GMR films on rad-hard integrated circuits, both the circuits and the films survived ionizing radiation levels consistent with DOE mission requirements. Furthermore, Sandia developed techniques to pattern deposited GMR films without degrading the completed integrated circuits upon which they were deposited. The present feasibility study demonstrated all the necessary processing elements to allow fabrication of the non-volatile memory elements onto an existing CMOS chip, and even allow the use of embedded (on-chip) non-volatile memories for system-on-a-chip applications, even in demanding radiation environments. However, funding agencies DTRA, AIM, and DARPA did not have any funds available to support the required follow-on technology development projects that would have been required to develop functioning prototype circuits, nor were such funds available from LDRD nor from other DOE program funds.

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127 Results
127 Results