Pulsed-laser Testing Research Articles

The Inflection Point of Single Event Transient in SiGe HBT at a Cryogenic Temperature

Basing our findings on our previous pulsed laser testing results, we have experimentally demonstrated that there is an inflection point of a single event transient (SET) in the silicon-germanium heterojunction bipolar transistors (SiGe HBTs) with a decreasing temperature from +20 °C to −180 °C. Additionally, the changes in the parasitic resistivity of the carrier collection pathway due to incomplete ionization could play a key role. In this paper, we found that the incident-heavy ion’s parameters could also have an important impact on the SET inflection point by introducing the ion track structures generated by Geant4 simulation to the TCAD transient simulation. Heavy ion with a low linear energy transfer (LET) will not trigger the ion shunt effect of SiGe HBT and the inflection point will not occur until −200 °C. For high LET ions’ incidence, the high-density electron-hole pairs (EHPs) could significantly affect the parasitic resistivity on the pathway and lead to an earlier inflection point. The present results and methods could provide a new reference for the effective evaluation of single-event effects in bipolar transistors and circuits at cryogenic temperatures and provide new evidence of the SiGe technology’s potential for applications in extreme cryogenic environments.

Pulsed-Laser Testing to Quantitatively Evaluate Latchup Sensitivity in Mixed-Signal ASICs

Pulsed-laser testing is used to accurately determine single-event latchup (SEL) thresholds for static random-access memories (SRAMs) with different body-tie-to-drain spacings on a mixed-signal application-specific integrated circuit (ASIC), a study that could not be completed using only broad-beam heavy-ion testing. Two distinct approaches were employed with the first approach, an empirical correlation method, exploiting the complementary nature of broad-beam heavy-ion and laser testing. Various single- and dual-port SRAMs exhibited SEL thresholds ranging from 1 MeV-cm²/mg to over 100 MeV-cm²/mg, with a dual-port device possessing the smallest body-tie-to-drain spacing being latchup immune at the highest available test conditions (>300 MeV-cm²/mg). These results have been used to inform a follow-on ASIC design resulting in a significant improvement in chip-level SEL sensitivity. The second approach, a calculational method, uses pulsed-laser measurements and charge-deposition modeling to predict linear energy transfer (LET) thresholds without heavy-ion data. This calculational approach agrees with the empirical approach and therefore shows promise as a predictive tool for SEL threshold estimation, but further validation is required. Overall, these approaches can be effective tools for evaluating SEL susceptibilities and mitigation strategies.

A highly reliable radiation hardened 8T SRAM cell design

In this paper, a new Radiation Hardened By Design (RHBD) 8T SRAM cell is proposed that can tolerate single-event upset (SEU) in a radiation environment. According to the simulation results for 130 nm silicon-on-insulator (SOI) technology, the critical charge of the proposed 8T cell increases by 82.9% compared to the conventional 6T SRAM cell and by 62.5% compared to the other RHBD SRAM cell, the Soft-error-Tolerant-10T (ST-10T) cell. Pulsed laser testing was used for SEU sensitivity evaluation. Further, the energy threshold of the proposed cell increases by 122.3% and 90.8%, respectively, compared to the conventional 6T cell and the ST-10T cell. Moreover, the proposed cell has a lower leakage current, higher read current, and larger read static noise margin (RSNM) compared to the other two cells. The total ionizing dose (TID) effects on the proposed 8T SRAM cell were also studied, and the results show that the proposed cell is insensitive to TID.

Mapping the Spatial Dependence of Charge-Collection Efficiency in Semiconductor Devices Using Pulsed-Laser Testing

By scanning the charge-deposition profile produced by a pulsed laser throughout a device, the spatially dependent charge-collection efficiency (CCE) can be determined. This is demonstrated by extracting the depth-dependent CCE in two photodiodes. The resulting collection efficiency curves are found to be consistent with their device structures and the expected charge-collection mechanisms. By applying the efficiency curves to the charge-deposition curves for both heavy ions and pulsed X-rays, the calculated collected charge values show very good agreement with experimental results. This suggests that the profiles extracted using the laser can help predict charge-collection data from other excitation sources and could improve modeling efforts by determining sensitive volumes.

Design of a High-Performance Low-Cost Radiation-Hardened Phase-Locked Loop for Space Application

In the harsh space environment, the phase-locked loop (PLL) circuit is vulnerable to radiation effects, which will lead to performance degradation or even function interrupts. In this article, a rad-hard low-noise PLL is designed with low power and area overhead and verified in a 130-nm silicon-on-insulator process. Heavy ion test demonstrates that the proposed PLL is immune to the single-event effect up to 83.7 MeV·cm2/mg. Furthermore, its single-event sensitivity is characterized and compared with an unhardened PLL by the pulsed laser test. Finally, the gamma-ray radiation experiment confirms that it can provide >300 krad(Si) total ionizing dose assurance.

Using Bessel beams and two-photon absorption to predict radiation effects in microelectronics.

Pulsed-laser testing is an attractive tool for studying space-based radiation effects in microelectronics because it provides a high degree of spatial resolution and is more cost-effective than conventional accelerator-based testing. However, quantitatively predicting the effects of radiation is challenging for this optical method. A new approach to pulsed-laser testing is presented, which addresses these challenges by using a Bessel beam and carrier generation via two-photon absorption. By producing a carrier distribution in the device under test that is similar to that of a heavy ion, this optical approach aims to quantitatively predict the response of the device under heavy ion tests that represent space radiation. Furthermore, the carrier distribution can be accurately described using a single analytic expression thereby enabling the laser to be tuned to emulate a specific heavy ion. Herein, we describe the modifications made to an existing pulsed-laser setup to generate this carrier distribution, characterize this distribution using a novel method that provides sub-micron spatial resolution, and provide the equations that describe the distribution. Finally, we use this method to study a silicon photodiode and find that the transient response of the device shows strong agreement with the response generated using heavy ions.

Polarization Dependence of Pulsed Laser-Induced SEEs in SOI FinFETs

Pulsed, laser-induced, single-event current measurements on silicon-on-insulator (SOI) FinFETs at subbandgap wavelength (1260 nm) are affected by the polarization of the laser light used in the experimental testing setup. Such polarization dependence is not observed during pulsed laser, single-event effects testing on large-area silicon diodes, suggesting that polarization dependence arises due to the presence of the nanoscale fin. Plasmonic enhancement is proposed as a likely mechanism for the polarization effects due to the metal/dielectric interfaces in the fin region. The observed polarization dependence has ramifications for collection and interpretation of data acquired by pulsed laser testing. Device orientation of FinFETs and other nanoscale devices during pulsed laser testing should be considered in order to ensure consistent testing conditions and reproducible measurement results across multiple measurement campaigns.

Comparison of Single-Event Transients in SiGe HBTs on Bulk and Thick-Film SOI

A comparison of heavy-ion-induced single-event transients (SETs) in silicon–germanium heterojunction bipolar transistors (SiGe HBTs) fabricated on both bulk and silicon-on-insulator (SOI) substrates is presented. Experimental heavy-ion data show a reduction of sensitive volume of $\approx 350\times $ for the SiGe HBTs fabricated on SOI compared to those on a bulk substrate. Furthermore, the results indicate that the sensitive volume of the SOI SiGe HBTs is confined to the intrinsic device. These results have been confirmed using pulsed laser data and TCAD simulations. Limiting the charge collection depth of SiGe HBTs by fabricating them on SOI facilitates correlation of ion and laser results. The improved ease of correlation is a result of suppressing diffusive charge collection mechanisms that are difficult to replicate with the charge deposition profile generated by two-photon absorption using a tightly focused laser beam. However, a potential issue with pulsed laser testing is determining the loss of the pulse energy through the buried oxide, which requires detailed knowledge of the semiconductor platform. Overall, the reduction of sensitive volume for the SOI SiGe HBTs compared to those on a bulk substrate is a clear advantage from a single-event upset vulnerability perspective.

New Approach for Pulsed-Laser Testing That Mimics Heavy-Ion Charge Deposition Profiles

A novel approach for two-photon absorption (TPA) pulsed-laser testing produces extended charge deposition profiles that are analogous to those produced by heavy ions. In this approach, which utilizes an axicon rather than a spherical lens, the conventional Gaussian beam is replaced by a quasi-Bessel beam. The key feature of a quasi-Bessel beam, relevant to pulsed-laser single-event effects (PL-SEE) studies, is that its radial size ( $\sim 1~\mu \text{m}$ ) remains constant over the axial length of the beam (several 100 s of $\mu \text{m}$ ) resulting in a charge-deposition profile that more closely mimics that produced by a heavy ion. This elongated charge distribution directly lends itself to a simple and intuitive description in terms of linear-energy transfer (LET), facilitating laser/ion correlation studies. Experimental results comparing a conventional TPA PL-SEE focusing geometry and the axicon focusing geometry are presented for three different test vehicles: a 45-nm silicon-on-insulator (SOI) nFET, a bulk silicon photodiode, and an LM124 operational amplifier. By using the axicon approach, strong laser/ion correlation is observed in the silicon photodiode for single-event transients (SET) across a wide range of LETs. The correlation is achieved by “tuning” the laser to the desired LET rather than relying on preexisting heavy-ion data, and therefore, this approach holds promise as a predictive tool.

Single Events Induced By Heavy Ions and Laser Pulses in Silicon Schottky Diodes

This paper is dedicated to the investigation of single-event effects (SEEs) in different types of silicon Schottky diodes using heavy ions and laser pulses. The objectives are both to progress in heavy ions and laser correlations using simple devices and to further understand the impact of optical and electrical parameters on photogeneration in Schottky diodes to contribute to the use of pulsed lasers for single-event sensitivity studies. Heavy ion test results on planar and trenched commercial Schottky diodes are presented. Based on these results, pulsed laser tests and transient measurements were performed on the sensitive devices. Destructive single events were evidenced with both techniques. Significant parameters of the laser tests, such as backside aperture of the device, electrical and optical configuration are discussed. These investigations show the potential of laser testing for Schottky diode SEE sensitivity study.

Utilizing SiGe HBT Power Detectors for Sensing Single-Event Transients in RF Circuits

This paper demonstrates the use of an RF power detector to sense the occurrence of single-event transients (SETs) in RF circuits and systems. The detector was connected to a low-noise amplifier (LNA), and the relationship between the detector output and the LNA transients was investigated via two-photon absorption, pulsed-laser testing, together with mixed-mode TCAD simulations. The response of the detector shows a strong correlation with the RF power of the generated SET. An analytical expression for the detector output is derived and utilized to fit the data. The effects of parameters affecting circuit performance on the detector response to SETs are explored using calibrated TCAD mixed-mode simulations, and design tradeoffs are presented. Finally, a solution to distinguish between transients generated in the detector from those generated in the circuit being monitored is proposed and verified in simulation. The use of detectors to monitor SETs in RF systems could lead to judicious deployment of detection-driven SET mitigation techniques.

Analysis of TPA Pulsed-Laser-Induced Single-Event Latchup Sensitive-Area

Two-photon absorption (TPA) pulsed-laser testing is used to analyze the TPA-induced single-event latchup sensitive-area of a specially designed test structure. This method takes into account the existence of an onset region in which the probability of triggering latchup transits between 0 and 1 as the laser pulse energy increases. This variability is attributed to a combination of laser pulse-to-pulse variability and variations in local carrier density and temperature. For each spatial position, the latchup probability associated with a given energy is calculated. Calculation of latchup cross section at lower laser energies, relative to onset, is improved significantly by taking into account the full probability distribution. The transition from low probability of latchup to high probability is more abrupt near the source contacts than for surrounding areas.

DAMSEL—Dynamic and Applicative Measurement of Single Events in Logic

This paper describes a circuit called dynamic and applicative measurement of single events in logic (DAMSEL), which can individually measure the impact of single event upsets and single-event transients (SETs) in realistic, synchronous digital circuits. Heavy-ion and pulsed laser test results are presented. Both a simple digital and an analog simulation methodology are demonstrated to provide similar cross sections to those observed during the tests. Overall, the DAMSEL structure has many advantages over current circuits used for measuring SETs, including the ease with which test results can be extrapolated to real designs.

Analysis of Single-Event Effects in a Radiation-Hardened Low-Jitter PLL Under Heavy Ion and Pulsed Laser Irradiation

A radiation-hardened low-jitter phase-locked loop (PLL) with a low-mismatch charge pump and a robust voltage-controlled oscillator is designed in a 130 nm PD-SOI process. In order to evaluate the overall response to single-event effects, the accumulated phase jitter has been put forward, which can exclude the inherent noise floor and accumulate all the radiation-induced noise. Then the single-event sensitivity of the proposed PLL is comprehensively analyzed by heavy ion and pulsed laser tests.

Laser Shielding and Thermal Ablation Characteristics of Resorcinol Formaldehyde/Boron Nitride Composites for Thermal Protection Systems

Resorcinol formaldehyde (RF) composites were modified by incorporating different weight ratios of hexagonal boron nitride (h-BN) through a novel in situ polymerization technique. Temperature modulated SAXS was used to understand the changes in polymer network due to h-BN addition. The ablation performance of RF–BN composites was evaluated by pulsed laser and oxyacetylene torch tests. Linear ablation resistance under oxyacetylene conditions improved by 18%. Laser ablation resistance increased by 44%. The reasons for improved ablation resistance for RF–BN composites were studied using XRD, FTIR, and XPS methods which indicated that h-BN undergoes phase transformation at higher temperatures and also displays typical floral assimilation leading to significant energy consumption. This results in improved ablation resistance. These findings could lead to fabrication of RF–BN based thermal protection systems (TPS) having better protection capabilities.

Single-Event Transient Characterization of a Radiation-Tolerant Charge-Pump Phase-Locked Loop Fabricated in 130 nm PD-SOI Technology

In this paper, a radiation-tolerant phase-locked loop (PLL) is designed and fabricated with 130 nm PD-SOI technology. A current-based charge pump is hardened using a current compensation technique in combination with the differential charge cancellation (DCC) layout of the complementary switches. Besides, the stacked SOI transistors are employed to mitigate single-event effects of the voltage-controlled oscillator. The experimental results show that the proposed PLL has no significant jitter variations under heavy-ion experiments, compared with TMR-hardened PLL. Besides, pulsed-laser testing comprehensively characterizes the single-event transients of the PLL and demonstrates its radiation tolerant performance.

The investigation on sensitive mapping of memory cell in microprocessor

The single event effects of the sensitivity of a circuit are investigated on a 32-bit microprocessor with a five-stage instruction pipeline by pulsed laser test. The investigation on sensitive mapping of the memory cell is illustrated and then the comparison between the sensitive mapping and the layout of the circuit is made. A comparison result indicates that the area of the sensitive node in sensitive mapping is just the location of the drain in the layout. Therefore, SEE sensitivity in sensitive mapping fits well with that in the physical layout of functional units, which can directly and objectively indicate the size and distribution of sensitive areas. The investigation of sensitive mapping is a meaningful way to verify the hardened effect and provide a reference for improving hardened design by combining with the physical layout.

Development and testing of cost-effective, 6 cm×6 cm MCP-based photodetectors for fast timing applications

Micro-channel plate (MCP)-based photodetectors are capable of picosecond level time resolution and sub-mm level position resolution, which makes them a perfect candidate for the next generation large area photodetectors. The large-area picosecond photodetector (LAPPD) collaboration is developing new techniques for making large-area photodetectors based on new MCP fabrication and functionalization methods. A small single tube processing system (SmSTPS) was constructed at Argonne National Laboratory (ANL) for developing scalable, cost-effective, glass-body, 6cm×6cm, picosecond photodetectors based on MCPs functionalized by Atomic Layer Deposition (ALD). Recently, a number of fully processed and hermitically sealed prototypes made of MCPs with 20μm pores have been fabricated. This is a significant milestone for the LAPPD project. These prototypes were characterized with a pulsed laser test facility. Without optimization, the prototypes have shown excellent results: the time resolution is ~57ps for single photoelectron mode and ~15ps for multi-photoelectron mode; the best position resolution is ≤0.8mm for large pulses. In this paper, the tube processing system, the detector assembly, experimental setup, data analysis and the key performance will be presented.

Fault Simulation and Emulation Tools to Augment Radiation-Hardness Assurance Testing

As of 2013, the gold standard for assessing radiation-hardness assurance (RHA) for a system, subsystem, or a component is accelerated radiation testing and/or pulsed laser testing. Fault injection tools, which include both fault simulation and emulation tools, have become more common in the last 15 years. Fault simulation tools use analytical methods for assessing RHA, whereas fault emulation uses hardware methods. Both fault simulation and emulation allow designers to augment traditional RHA techniques to determine whether circuit designs, microarchitectures, components, and application-specific integrated circuits (ASICs) meet the requirements for a particular mission. Fault simulation and emulation can provide the designers the luxury of testing on the benchtop without the time and financial constraints of accelerated radiation testing. This paper explores how to design, implement, and validate a fault simulation or emulation system. The paper ends with several case studies of currently used fault simulation and emulation systems.

Correlation of Heavy-Ion and Laser Testing on a DC/DC PWM Controller

Pulsed laser and heavy-ion experiments were carried out on a commercial-off-the-shelf DC/DC pulse width modulation controller to study the equivalent laser Linear Energy Transfer (LET) at wavelengths of 750 nm, 800 nm, 850 nm and 920 nm. The laser experiments showed that the shorter wavelength laser has smaller threshold energy to generate single-event transient pulses. The cross-sections versus heavy-ion LET and laser energy per pulse were obtained and correlated. The heavy-ion and laser cross-sections fit well considering the effects of metal layers on the chip. The results of this research facilitate the future pulsed laser testing by providing explicit coefficients to evaluate the equivalent laser LET, which can be used to replace costly heavy-ion testing.