Engineering topics
Publications and source records attributed to Phan, Anthony.
We show heavy ion test results of a commercial production-level ReRAM. The memory array is robust to bit upsets. However the ReRAM system is vulnerable to SEFIs due to upsets in peripheral circuits, including the sense amplifier.
Finite state-machines (FSMs) are used to control operational flow in application specific integrated circuits (ASICs) and field programmable gate array (FPGA) devices. Because of their ease of interpretation, FSMs simplify the design and verification process and consequently are significant components in a synchronous design.
In this presentation, we provide a brief glimpse at preliminary single event test results taken from two years of testing of the Xilinx V5QV Field Programmable Gate Array (FPGA). This presentation includes an overview of test philosophy and implementation.
We show examples of single event functional interrupt and destructive failure in modern POL devices. The increasing complexity and diversity of the design and process introduce hard SEE modes that are triggered by various mechanisms.
We present results on the effects on ELDRS at dose rates of 10, 5, 1, and 0.5 mrad(Si)/s for a variety of radiation hardened and commercial devices. We observed low dose rate enhancement below 10 mrad(Si)/s in several different parts. The magnitudes of the dose rate effects vary. The TL750L, a commercial voltage regulator, showed dose rate dependence in the functional failures, with initial failures occurring after 10 krad(Si) for the parts irradiated at 0.5 mrad(Si)/s. The RH1021 showed an increase in low dose rate enhancement by 2x at 5 mrad(Si)/s relative to 8 mrad(Si)/s and high dose rate, and parametric failure after 100 krad(Si). Additionally the ELDRS-free devices, such as the LM158 and LM117, showed evidence of dose rate sensitivity in parametric degradations. Several other parts also displayed dose rate enhancement, with relatively lower degradations up to approx.15 to 20 krad(Si). The magnitudes of the dose rate enhancement will likely increase in significance at higher total dose levels.
We have presented results of ultra-low dose rate irradiations (< or = 10 mrad(Si)/s) for a variety of radiation hardened and commercial linear bipolar devices. We observed low dose rate enhancement factors exceeding 1.5 in several parts. The worst case of dose rate enhancement resulted in functional failures, which occurred after 10 and 60 krad(Si), for devices irradiated at 0.5 and 10 mrad(Si)/s, respectively. Devices fabricated with radiation hardened processes and designs also displayed dose rate enhancement at below 10 mrad(Si)/s. Furthermore, the data indicated that these devices have not reached the damage saturation point. Therefore the degradation will likely continue to increase with increasing total dose, and the low dose rate enhancement will further magnify. The cases presented here, in addition to previous examples, illustrate the significance and pervasiveness of low dose rate enhancement at dose rates lower than 10 mrad(Si). These results present further challenges for radiation hardness assurance of bipolar linear circuits, and raise the question of whether the current standard test dose rate is conservative enough to bound degradations due to ELDRS.
We present results on heavy-ion and proton irradiations for commercial SiGe BiCMOS operational amplifiers: LTC6400-20 from Linear Technology and THS4304 from Texas Instruments. We found that the devices are susceptible to heavy-ion-induced SETs. The SET cross-sections increase with increasing operating frequency. The LTC6400 exhibits a LET(sub th) < 7.4 MeV·sq cm/mg for frequencies ranging from 10 to 1000 MHz. The THS4304 exhibits a LET(sub th) < 4.4 MeV·sq cm/mg at 200 MHz; the LET(sub th) decreases with increasing frequency. The significance of the SETs also increases with frequency. The SETs at 1000 MHz can erase several signal cycles. We al.so found that the LTC6400 is relatively robust against 198 and 54 MeV protons. We did not observe angular sensitivity from the proton irradiations.
We present results of ultra-low dose-rate irradiations on a variety of commercial and radiation hardened bipolar circuits. We observed enhanced degradations at dose rates lower than 10 mrad(Si)/s in some devices.
Single-event gate rupture (SEGR) is a potentially catastrophic failure mechanism of power MOSFETs biased in the off-state. In part due to the severity of-SEGR consequences and in part due to the difficulty of accurated SEGR rate estimation, SEGR mitigation me1hodologies emphasize risk avoidance, using heavy-ion accelerator testing to define safe operating conditions for a surface-incident linear energy transfer {LET). This "safe-operating area" (SOA) within which the device may be biased without experiencing SEGR is then often derated by a prescribed factor to ensure low risk of SEGR. Although research in 1996 indicated that such LET-based SEGR hardness requiremen1s could provide false assurance of safe operation unless one also considered· ion energy], most mission SEGR requirements are still specified in terms of surface-incident LET. Moreover, terrestrial SEGR tests at a given surface-incident LET are limited by the small number of ion species and energies available at heavy-ion accelerators. In comparison, the on-orbit radiation environment is composed of all of the naturally-occurring elements with peak fluxes at nearly GeV/nucleon energies. The primary objective of this study is to examine whether typical derating of high-energy heavy-ion accelerator test data bounds the risk for SEGR from higher-energy on-orbit ions with the mission LET requirement.
Use of low-energy protons and high-energy light ions is becoming necessary to investigate current-generation SEU thresholds. Systematic errors can dominate measurements made with low-energy protons. Range and energy straggling contribute to systematic error. Low-energy proton testing is not a step-and-repeat process. Low-energy protons and high-energy light ions can be used to measure SEU cross section of single sensitive features; important for simulation.
As with other bipolar analog devices, voltage regulators are known to be sensitive to single event transients (SET). In typical applications, large output capacitors are used to provide noise immunity. Therefore, since SET amplitude and duration are generally small, they are often of secondary importance due to this capacitance filtering. In low voltage applications, however, even small SET are a concern. Over-voltages may cause destructive conditions. Under-voltages may cause functional interrupts and may also trigger electrical latchup conditions. In addition, internal protection circuits which are affected by load as well as internal thermal effects can also be triggered from heavy ions, causing dropouts or shutdown ranging from milliseconds to seconds. In the case of FPGA power supplies applications, SETS are critical. For example, in the case of Actel FPGA RTAX family, core power supply voltage is 1.5V. Manufacturer specifies an absolute maximum rating of 1.6V and recommended operating conditions between 1.425V and 1.575V. Therefore, according to the manufacturer, any transient of amplitude greater than 75 mV can disrupt normal circuit functions, and overvoltages greater than 100 mV may damage the FPGA. We tested five low dropout voltage regulators for SET sensitivity under a large range of circuit application conditions.
We present radiation data, Total Ionizing Dose and Single Event Effects, on the LSI Logic 0.11 micron commercial process and two modified versions of this process. Modified versions include a buried layer to guarantee Single Event Latchup immunity.