Z. J. Diggins

Technology Scaling Comparison of Flip-Flop Heavy-Ion Single-Event Upset Cross Sections

Heavy-ion experimental results from flip-flops in 180-nm to 28-nm bulk technologies are used to quantify single-event upset trends. The results show that as technologies scale, D flip-flop single-event upset cross sections decrease while redundant storage node flip-flops cross sections may stay the same or increase depending on the layout spacing of storage nodes. As technology feature sizes become smaller, D flip-flop single-event upset cross sections approach redundant storage node hardened flip-flops cross sections for particles with high linear energy transfer values. Experimental results show that redundant storage node designs provide > 100X improvement in single-event upset cross section over DFF for ion linear energy transfer values below 10 MeV-cm2/mg down to 28-nm feature sizes.

Estimation of hardened flip-flop neutron soft error rates using SRAM multiple-cell upset data in bulk CMOS

Experimental neutron single-event error rates of 28-and 40-nm bulk CMOS hardened flip-flops are compared to various hardened flip-flop designs in literature. Using published 45-nm SRAM multiple-cell upset data, it is shown that the error rate of hardened flip-flop designs can be estimated by using the minimum sensitive node spacing from the flip-flop layout. Experimental data show that regardless of circuit topology of a hardened flip-flop, the redundant storage node spacing dominates neutron soft-error rates.

Neutron- and alpha-particle induced soft-error rates for flip flops at a 40 nm technology node

Flip-flop designs fabricated in a 40 nm bulk technology node with a wide range of soft-error hardness, area, power, and speed have been tested for neutron and alpha single event upsets. Neutron results show that the error rates of flip-flop designs that were considered hardened at older technologies are comparable to that of the conventional D-flip-flop. The soft-error rates (SER) of all the flip-flops consistently increase with reduction in supply voltage and increase in ambient temperature.

Range-Finding Sensor Degradation in Gamma Radiation Environments

The effects of gamma radiation on common sensors used in robots intended for nuclear remediation scenarios are examined. Commercial rangefinders are chosen as an exemplar of the impact of gamma radiation on sensors and systems. This paper illustrates sensor radiation degradation not only in operational failure, but also in changes in the sensor transfer function. Three types of commercial range-finding sensors are considered [infrared (IR) triangulation using a position sensitive detector, sonar using time of flight, and laser rangefinder using triangulation and a CMOS camera]. Experimental results show significant changes in the IR sensors static sensitivity with dose, abrupt failure of the laser range finder at low dose, and degradation and abrupt failure for the sonar detector. The input-output relationship of the IR sensor showed further variation after a period of room-temperature annealing. Significant part-to-part variation in radiation response is shown for both the sonar and IR sensor. System level impacts due to sensor input-output relationship degradation and a technique to diagnose the degradation extendable to more complex sensor assemblies are presented.

Effect of threshold voltage implants on single-event error rates of D flip-flops in 28-nm bulk CMOS

To understand the effects of threshold voltage implants on soft-error rate of a D flip-flop, three different designs were created using low, standard, and high voltage threshold implants in a 28-nm bulk technology. Experimental results show that the error rate is nearly the same for the three D flip-flop designs. This work attributes small critical charge and process variations across the flip-flop arrays as the main cause for similar soft-error rate of the flip-flops regardless of the threshold voltage implant.

Impact of gamma radiation on range finding sensor performance

The effect of gamma radiation on common sensors in robots intended for nuclear remediation scenarios is examined. Rangefinders are chosen as an exemplar of the impact of gamma radiation on sensors and systems. This work extends previous work by calculating not just sensor failure point but changes in the sensor transfer function of three different types of commercial range-finding sensors (infrared (IR) triangulation using a position sensitive detector, sonar using time of flight, and laser range finder using triangulation and a CMOS camera) in response to gamma total radiation dose. Experimental results show significant changes in the IR sensors static sensitivity with dose, abrupt failure of the laser range finder at low dose, and degradation and abrupt failure for the sonar detector. The input-output relationship of the IR sensor showed further variation after a period of room-temperature annealing. Significant part-to-part variation in radiation response is shown for both the sonar and IR sensor.

Scalability of Capacitive Hardening for Flip-Flops in Advanced Technology Nodes

Capacitive radiation hardening by design (RHBD) techniques to reduce the single-event cross section of flip-flops are shown to be effective at highly scaled technology nodes, especially for the terrestrial environment. Test results for different values of RHBD capacitance for both 40 nm and 28 nm technology node designs show that small values of RHBD capacitance (<; 3 fF) are effective in reducing the single-event cross section for low LET particles, neutrons, and alpha particles. Reductions of 4x, 2.5x, and 14x respectively were observed for the 28 nm designs for low LET particles, neutrons, and alpha particles, and reductions of 2.4x and 2.1x were observed for the 40 nm designs for low LET particles and alpha particles. Experimental pulse width measurement results for Xenon are used to highlight operating regions where capacitive RHBD techniques are most effective.

Soft error rate comparison of various hardened and non-hardened flip-flops at 28-nm node

For flip-flop designs fabricated at advanced technology nodes, soft errors are expected to contribute significantly to the overall failure-in-time rates for electronic systems. Since the soft error rates are design and layout dependent, it is important to evaluate different flip-flop designs used in an electronic system. Alpha-particle, high-energy proton, neutron, and heavy-ion experimental results of 30 different flip-flop designed and manufactured in a 28-nm bulk CMOS process are presented in this paper. The results show the spectrum of soft error rates a system-level designer may see for hardened and non-hardened flip-flops at the 28-nm bulk CMOS technology node.

Angled flip-flop single-event cross sections for submicron bulk CMOS technologies

Experimental angled heavy-ion single-event cross sections for hardened and unhardened flip-flops for technology nodes ranging from 28-nm to 130-nm are compared. Results show that hardened flip-flop cross sections increase at a faster rate with increasing angle of incidence than unhardened designs as technology scales. Hardened flip-flop cross section approaches unhardened flip-flop cross section for high incidence angular strikes, and surpasses unhardened flip-flop cross sections at 28-nm feature sizes.

Effects of Temperature and Supply Voltage on SEU- and SET-Induced Errors in Bulk 40-nm Sequential Circuits

The single-event sensitivity of bulk 40-nm sequential circuits is investigated as a function of temperature and supply voltage. An overall increase in SEU cross section versus temperature is observed at relatively high supply voltages. However, at low supply voltages, there is a threshold temperature beyond which the SEU cross section decreases with further increases in temperature. Single-event transient induced errors in flip-flops also increase versus temperature at relatively high supply voltages and are more sensitive to temperature variation than those caused by single-event upsets.