S.D. Phillips

Georgia Institute of Technology, Atlanta, Georgia, United States

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Publications (28)30.56 Total impact

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    ABSTRACT: Electronics in space-based systems are in the process of a paradigm shift moving from centralized, heavily shielded, temperature-controlled warm boxes to distributed, minimally shielded sensing and control nodes. SiGe BiCMOS technology is one of the enablers of this move with its ability to withstand extremely wide variations in temperature and high radiation doses. This article has presented two SiGe BiCMOS wireline transceivers designed to be a part of the new system perspective by creating a means of control and communication across vehicle-wide buses. Both the RS-485 and ISO 11898 transceivers have been shown to work robustly from 90 K to 390 K, with consistent rise/fall times, propagation delays, and output amplitudes. Additionally, the ISO 11898 transceiver is TID tolerant to 2 Mrad, and the transmitter is hardened to single-event effects.
    IEEE Aerospace and Electronic Systems Magazine 01/2014; 29(3):32-41. · 0.34 Impact Factor
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    ABSTRACT: The single-event effect sensitivity of fourth-generation, 90 nm SiGe HBTs is investigated. Inverse-mode, $ geq 1.0~hbox{Gbps}$ SiGe digital logic using standard, unoptimized, fourth-generation SiGe HBTs is demonstrated and the inverse-mode shift register exhibited a reduction in bit-error cross section across all ion-strike LETs. Ion-strike simulations on dc calibrated, 3-D TCAD SiGe HBT models show a reduction in peak current transient magnitude and a reduction in overall transient duration for bulk SiGe HBTs operating in inverse mode. These improvements in device-level SETs are attributed to the electrical isolation of the physical emitter from the subcollector-substrate junction and the high doping in the SiGe HBT base and emitter, suggesting that SiGe BiCMOS technology scaling will drive further improvements in inverse-mode device and circuit-level SEE. Two-photon absorption experiments at NRL support the transient mechanisms described in the device-level TCAD simulations. Fully-coupled mixed-mode simulations predict large improvements in circuit-level SEU for inverse-mode SiGe HBTs in multi-Gbps, inverse-mode digital logic.
    IEEE Transactions on Nuclear Science 01/2013; 60(6):4175-4183. · 1.22 Impact Factor
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    ABSTRACT: Single-event transient simulations are performed on a Gb/s SiGe BiCMOS master/slave D flip-flop circuit, employing both a decoupled current-injection SET modeling technique and a fully-coupled mixed-mode TCAD technique to model heavy-ion strikes to the storage and input cells. New insights are provided into the physical mechanisms underlying the SEU sensitivity of high-speed SiGe digital latches and shift registers. A close analysis of the transient circuit behavior identifies the limitations of the current-injection approach in predicting SEU in fast SiGe digital logic. Finally, the physical ion track LET is varied to establish the threshold LET for SEU using each simulation technique, further highlighting the SEU prediction error inherent to conventional decoupled modeling approaches.
    RADECS; 09/2012
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    ABSTRACT: The total ionizing dose and laser-induced transient response of a new 4th generation 90 nm IBM SiGe 9HP technology are investigated. Total dose testing was performed with 63.3 MeV protons at the Crocker Nuclear Laboratory at the University of California, Davis. Transient testing was performed on the two-photon absorption system at Naval Research Laboratory. Results show that the SiGe HBTs are dose-tolerant up to 3 Mrad(SiO2) and exhibit reduced single event transients compared to earlier SiGe generations.
    Radiation Effects Data Workshop (REDW), 2012 IEEE; 01/2012
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    ABSTRACT: The single-event effect sensitivity of inverse-mode biased SiGe HBTs in both bulk and SOI technology platforms are investigated, for the first time, using digital circuits and stand-alone device test structures. Comparisons of heavy-ion broad beam data of shift register circuits constructed with forward-mode and inverse-mode biased SiGe HBTs from a first-generation, complementary SOI SiGe BiCMOS process, reveal an improvement in SEU mitigation for the inverse-mode shift register architecture. Full 3D TCAD simulations highlight the differences in transient current origination between forward and inverse-mode biased devices, illustrating the impact of doping profiles on ion-induced shunt duration. To extend the analysis to a bulk platform, new fourth-generation npn , SiGe HBTs were biased in both the forward and inverse-mode and irradiated at NRL using the two photon absorption measurement system. These measurements support the analysis of transient origination using 3D TCAD simulations. Furthermore, the isolation of the output terminal from the sensitive subcollector-substrate junction is experimentally demonstrated for the inverse-mode bias. Fully coupled mixed-mode simulations predict a significant reduction in sensitive area for inverse-mode shift registers built in a bulk SiGe platform.
    IEEE Transactions on Nuclear Science 01/2012; 59(6):2682-2690. · 1.22 Impact Factor
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    ABSTRACT: Single-event transient (SET) simulations of a Gb/s SiGe BiCMOS master/slave D flip-flop circuit are performed, employing both a decoupled current-injection SET modeling technique and a fully-coupled mixed-mode TCAD technique to model heavy-ion strikes to the storage and input cells. New insights are provided into the physical mechanisms underlying the single-event upset (SEU) sensitivity of high-speed SiGe digital latches and shift registers. A close analysis of the transient circuit behavior identifies the limitations of the current-injection approach in predicting SEU in fast SiGe digital logic. Furthermore, the physical ion track linear energy transfer (LET) is varied to establish the threshold LET for SEU using each simulation technique, further highlighting the SEU prediction error inherent to conventional decoupled modeling approaches. Finally, clocked mixed-mode circuit simulations are used to explain the fundamental SEU mechanisms and relate them to corresponding regions of the device-level SET.
    IEEE Transactions on Nuclear Science 01/2012; 59(4):958-964. · 1.22 Impact Factor
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    ABSTRACT: An analysis of charge pump design for improved radiation tolerance of phase locked loops is presented. Two radiation-hardened-by-design approaches are considered to mitigate the total ionizing dose damage of the circuit, and a thick-film SOI SiGe process technology has been used to reduce charge collection of single event strikes. The results show that a modified design approach to implement the charge pump using SiGe HBTs can provide advantages in radiation tolerance to improve tri-state leakage performance, particularly for missions expecting large accumulated doses.
    IEEE Transactions on Nuclear Science 01/2011; 58(6):3038-3045. · 1.22 Impact Factor
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    ABSTRACT: A theory of the circuit-based response to SET phenomena in resonant tank oscillators is presented. Transients are shown to be caused by a change in the voltage state of the circuit's characteristic differential equation. The SET amplitude and phase response is derived for arbitrary strike waveforms and shown to be time-variant based on the strike time relative to the period of oscillation. Measurements in the time-domain are used to support the theory, while the frequency-domain is used to gauge potential impact on system performance. A design-oriented analysis of the relevant trade-offs is also presented.
    IEEE Transactions on Nuclear Science 01/2011; · 1.22 Impact Factor
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    ABSTRACT: We report on the design and measured results of a new SiGe HBT radiation hardening by design technique called the “inverse-mode cascode” (IMC). A third-generation SiGe HBT IMC device was tested in a time resolved ion beam induced charge collection (TRIBICC) system, and was found to have over a 75% reduction in peak current transients with the use of an n-Tiedown on the IMC sub-collector node. Digital shift registers in a 1st-generation SiGe HBT technology were designed and measured under a heavy-ion beam, and shown to increase the LET threshold over standard npn only shift registers. Using the CREME96 tool, the expected orbital bit-errors/day were simulated to be approximately 70% lower with the IMC shift register. These measured results help demonstrate the efficacy of using the IMC device as a low-cost means for improving the SEE radiation hardness of SiGe HBT technology without increasing area or power.
    IEEE Transactions on Nuclear Science 01/2011; · 1.22 Impact Factor
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    ABSTRACT: We investigate the efficacy of mitigating radiation-based single event effects (SEE) within circuits incorporating SiGe heterojunction bipolar transistors (HBTs) built with an N-Ring, a transistor-level layout-based radiation hardened by design (RHBD) technique. Previous work of single-device ion-beam induced charge collection (IBICC) studies has demonstrated significant reductions in peak collector charge collection and sensitive area for charge collection; however, few circuit studies using this technique have been performed. Transient studies performed with Sandia National Laboratory's (SNL) 36 MeV <sup>16</sup>O microbeam on voltage references built with N-Ring SiGe HBTs have shown mixed results, with reductions in the number of large voltage disruptions in addition to new sensitive areas of low-level output voltage disturbances. Similar discrepancies between device-level IBICC results and circuit measurements are found for the case of digital shift registers implemented with N-Ring SiGe HBTs irradiated in a broadbeam environment at Texas A&M's Cyclotron Institute. The error cross-section curve of the N-Ring based register is found to be larger at larger ion LETs than the standard SiGe register, which is clearly counter-intuitive. We have worked to resolve the discrepancy between the measured circuit results and the device-level IBICC measurements, by re-measuring single-device N-Ring SiGe HBTs using a time-resolved ion beam induced charge (TRIBIC) set-up that allows direct capture of nodal transients. Coupling these measurements with full 3-D TCAD simulations provides complete insight into the origin of transient currents in an N-Ring SiGe HBT. The detailed structure of these transients and their bias dependencies are discussed, together with the ramifications for the design of space-borne analog and digital circuits using SiGe HBTs.
    IEEE Transactions on Nuclear Science 01/2011; · 1.22 Impact Factor
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    ABSTRACT: We investigate the single-event transient (SET) response of T-body and notched-body contacted MOSFETs from a commercial 45 nm SOI RF-CMOS technology. Although body-contacted devices suffer from reduced RF performance compared to floating body devices, previous work on 65 nm and 90 nm MOSFETs has shown that the presence of a body-contact significantly mitigates the total ionizing dose (TID) sensitivity that is exhibited in floating-body SOI MOSFETs. The influence of body-contacting schemes on the single-event effect (SEE) sensitivity is examined here through time-resolved measurements of laser and microbeam-induced transients from T-body and notched-body MOSFETs. Laser-induced transients demonstrate the reduced SEE sensitivity of the notched-body MOSFETs as compared to the T-body MOSFETs; this is evidenced by a uniform reduction in the peak transient magnitudes and collected charge for transients captured at the worst-case bias of V<sub>DS</sub> = 1.0 V, as well as with all terminals grounded. Microbeam-induced transient data are also presented to support the validity of the laser-induced transient data. Together, these data provide new insight into the RF versus TID versus SEE tradeoffs associated with body contacting schemes in nm-scale MOSFETs, an important concern for emerging space-based electronics applications.
    IEEE Transactions on Nuclear Science 01/2011; · 1.22 Impact Factor
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    ABSTRACT: We report heavy-ion microbeam and total dose data for a new complementary (npn + pnp) SiGe on thick-film SOI technology. Measured transient waveforms from heavy-ion strikes indicate a significantly shortened single-event-induced transient current, while maintaining the total dose robustness associated with SiGe devices. Heavy-ion broad-beam data confirm a reduced single event upset (SEU) cross-section in a high-speed shift register circuit.
    IEEE Transactions on Nuclear Science 01/2011; · 1.22 Impact Factor
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    ABSTRACT: We report new results from both broad-beam, heavy-ion and proton experiments for circuit-level RHBD techniques in SiGe digital logic. Redundant circuit elements within the latches are used to significantly reduce single-event upset rates in shift registers and clock paths, without resorting to TMR techniques.
    IEEE Transactions on Nuclear Science 09/2010; · 1.22 Impact Factor
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    ABSTRACT: We investigate a novel implementation of junction isolation to harden a 200 GHz SiGe:C HBT technology without deep trench isolation against single event effects. The inclusion of isolation is shown to have no effect on the dc or ac performance of the nominal device, and likewise does not reduce the HBTs inherent tolerance to TID radiation exposure on the order of a Mrad. A 69% reduction in total integrated charge collection across a slice through the center of the device was achieved. In addition, a 26% reduction in collected charge is reported for strikes to the center of the emitter. 3-D NanoTCAD simulations are performed on RHBD and control device models yielding a good match to measured results for strikes from the emitter center to 8 ¿m away. This result represents one of the most effective transistor layout-level RHBD approaches demonstrated to date in SiGe.
    IEEE Transactions on Nuclear Science 01/2010; · 1.22 Impact Factor
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    ABSTRACT: Silicon-germanium heterojunction bipolar transistor (SiGe HBT) heavy ion-induced current transients are measured using Sandia National Laboratories' microbeam and high- and low-energy broadbeam sources at the Grand Acce¿le¿rateur National d'Ions Lourds, Caen, France, and the University of Jyva¿skyla¿, Finland. The data were captured using a custom broadband IC package and real-time digital phosphor oscilloscopes with at least 16 GHz of analog bandwidth. These data provide detailed insight into the effects of ion strike location, range, and LET.
    IEEE Transactions on Nuclear Science 01/2010; · 1.22 Impact Factor
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    ABSTRACT: We investigate, for the first time, the potential for SEE mitigation of a newly-developed device architecture in a 3rd generation high-speed SiGe platform. This new device architecture is termed the ¿inverse-mode cascode SiGe HBT¿ and is comprised of two standard devices sharing a buried subcollector and operated in a cascode configuration. Verification of the TID immunity is demonstrated using 10 keV X-rays, while an investigation of the SEE susceptibility is performed using a 36 MeV <sup>16</sup>O ion. IBICC results show strong sensitivities to device bias with only marginal improvement when compared to a standard device; however, by providing a conductive path from the buried subcollector (C-Tap) to a voltage potential, almost all collected charge is induced on the C-Tap terminal instead of the collector terminal. These results are confirmed using full 3-D TCAD simulations which also provides insight into the physics of this new RHBD device architecture. The implications of biasing the C-Tap terminal in a circuit context are also addressed.
    IEEE Transactions on Nuclear Science 01/2010; · 1.22 Impact Factor
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    ABSTRACT: We investigate the single-event transient (SET) response of bandgap voltage references (BGRs) implemented in SiGe BiCMOS technology through heavy ion microbeam experiments. The SiGe BGR circuit is used to provide the input reference voltage to a voltage regulator. SiGe HBTs in the BGR circuit are struck with 36-MeV oxygen ions, and the subsequent transient responses are captured at the output of the regulator. Sensitive devices responsible for generating transients with large peak magnitudes (more than 5% of the dc output voltage) are identified. To determine the effectiveness of a transistor-layout-based radiation hardened by design (RHBD) technique with respect to immunity to SETs at the circuit level, the BGR circuit implemented with HBTs surrounded by an alternate reverse-biased pn junction (n-ring RHBD) is also bombarded with oxygen ions, and subsequent SETs are captured. Experimental results indicate that the number of events causing transients with peak magnitude more than 5% above the dc level have been reduced in the RHBD version; however, with the inclusion of the n-ring RHBD, new locations for the occurrence of transients (albeit with smaller peak magnitude) are created. Transients at the transistor-level are also independently captured and are presented. It is demonstrated that while the transients are short at the transistor level (ns duration), relatively long transients are obtained at the circuit level (hundreds of nanoseconds). In addition, the impact of the SET response of the BGR on the performance of an ultra-high-speed 3-bit SiGe analog-to-digital converter (ADC) is investigated through simulation. It is shown that ion-induced transients in the reference voltage could eventually lead to data corruption at the output of the ADC.
    IEEE Transactions on Nuclear Science 01/2010; · 1.22 Impact Factor
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    ABSTRACT: SiGe HBTs are very attractive devices to be used in space communication applications. This technology combines the high speed of the III–V semiconductors with the well-established and easy manufacturing processes of silicon, which allows the manufacturing of RF, analog, and digital devices on the same wafer. In addition, SiGe HBTs were found to be extremely radiation hard in the context of total ionizing dose and displacement damage. However, it was shown through experiments and simulations that these devices are vulnerable to single event effects (SEEs). SEEs are changes in the normal operation of the device (its logical state, currents, transients, etc.) due to the induced currents in the electrodes by the movement of carriers created by the incident ions. We used four electrode (base, emitter, collector, and substrate) IBIC measurements at the Sandia Heavy Ion Nuclear Microprobe Facility. SiGe HBTs are usually designed using deep trench isolation (DTI) to minimize parasitic capacitances from the subcollector to the substrate (faster speed), as well as allow devices to be fabricated much closer together. It is an added bonus that the DTI does not let carriers from outside hits to diffuse into the junction and induce current. Our experiments and TCAD simulations showed that while the above goal was accomplished by this design, it increased the amount of induced charge for ion hits in the active area. Single event transients (SETs) were investigated in both standard and radiation hardened by design (RHBD) bandgap voltage reference (BGR) circuits.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2010; 268:2092-2098. · 1.27 Impact Factor
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    ABSTRACT: We present a novel device structure using an inverse-mode, cascoded (IMC) SiGe HBT for improved tolerance of heavy ion irradiation. The cascoded SiGe device consists of a forward-mode, common-emitter SiGe HBT cascoded with a common-base inverse-mode SiGe HBT, with the subcollector region of the two devices shared. The device was fabricated in both first and third-generation, commercially-available SiGe HBT technologies. The third-generation IMC device was measured to have over 20 dB of current gain and over 30 dB of power gain at 10 GHz. In addition, the measured total dose radiation response and simulated current transients are presented. These results demonstrate the potential use of these devices in high-speed circuits intended for operation in space or other extreme environments.
    Bipolar/BiCMOS Circuits and Technology Meeting, 2009. BCTM 2009. IEEE; 11/2009
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    ABSTRACT: The effects of 63 MeV proton irradiation on 65 nm Silicon-On-Insulator (SOI) CMOS technology are presented for the first time. The radiation response of the CMOS devices was investigated up to an equivalent total gamma dose of 4.1 Mrad (SiO<sub>2</sub>). We analyze the implications of proton irradiation on RF performance of these devices. The cut-off frequency is degraded due to post-irradiation degradation of device transconductance. High-frequency measurements show that the input and output matching conditions are not affected, up to a cumulative dose of 4.1 Mrad. The implications of proton irradiation on device design constraints, particularly device width and number of gate fingers, are discussed in the context of high performance RF CMOS technology. These results suggest that multi-finger CMOS devices with higher finger width are better-suited for the development of total-dose radiation tolerant analog and RF circuits without additional radiation hardening.
    IEEE Transactions on Nuclear Science 09/2009; · 1.22 Impact Factor