Leif Z. Scheick

TID, SEE and radiation induced failures in advanced flash memories

We report on TID and SEE tests of multi-level and higher density flash memories. Standby currents and functionality tests were used to characterize the response of radiation induced failures. The radiation-induced failures can be categorized as following: SEU read errors during irradiation, stuck-bit read errors verified post-irradiation, write errors, erase failures, multiple upsets, and single-event latch up.

Analysis of radiation effects on individual DRAM cells

A novel way to measure the radiation characteristics of DRAM memory cells is presented. Radiation exposure tends to drive retention times lower for cells. The change in retention time (the time period required for a cell to upset without refreshing) is used to measure the effect of irradiation on the DRAM cells. Both the radiation response of a single DRAM cell and the response of all cells as a statistical whole are analyzed.

Displacement damage-induced catastrophic second breakdown in silicon carbide Schottky power diodes

A novel catastrophic breakdown mode in reverse biased silicon carbide diodes has been seen for particles that are too low in LET to induce SEB, however SEB-like events were seen from particles of higher LET. The low LET breakdown mechanism correlates with second breakdown in diodes due to increased leakage and assisted charge injection from incident particles. Percolation theory was used to predict some basic responses of the devices.

Ion-induced stuck bits in 1T/1C SDRAM cells

Radiation exposure of certain types of devices tends to stick bits, causing them to not be read out correctly after programming. Evidence of a linear trend in stuck bits in SDRAM memory cells is presented. This trend makes a cross section, as traditionally defined for single-event effects, unambiguous. However, there are considerable part-to-part variations in the cross section.

SEU evaluation of SRAM memories for space applications

SEU cross-sections were obtained for three different SRAM memories. The 1 Mbit White Electronics WMS128k8, the 256 kbit Austin MT5C2564 and the 256 kbit Austin MT5C2568 SRAMs were tested. The SEU thresholds, respectively were 1 MeV cm/sup 2//mg, 1.4 MeV cm/sup 2//mg, and 1.8 MeV cm/sup 2//mg. SEL thresholds were also obtained. These were 37 MeV cm/sup 2//mg, 37 MeV cm/sup 2//mg and 59 MeV cm/sup 2//mg, respectively.

Radiation Effects in Power Systems: A Review

To guarantee mission success and minimize the risk of anomalies in space, current space-power architectures are designed conservatively and use electronics that are several generations behind the current state of the art. In parallel, the commercial industry is burgeoning with exciting new solutions for power management; however, their reliability and radiation robustness for space application have yet to be proven. The goal of this paper is to review common radiation issues related to power converters, which are the main design blocks of current space power system architectures. We first provide some background material and introduce the basic principles of power converter operation, as well as a brief introduction of common radiation effect that might damage these designs. Then, we explain common radiation-induced failure mechanisms (radiation-induced failure or instability) or temporary perturbations observed in various converter topologies. Their radiation hardness is compared based on simulation and experimental studies reported in the literature. Some radiation hardening by design solutions and mitigation techniques are also presented. Finally, we provide a status of emerging technologies under consideration for the next-generation of space power systems.

First failure predictions for EPROMs of the type flown on the MPTB satellite

Extreme value analysis applied to ground test data provides a new method for predicting the first cell to fail in an array of EPROM memory cells exposed to ionizing radiation. Which cell fails first is a function of the dose absorbed by each as well as the cell-to-cell variations in manufacturing with processing variations apparently dominating fluctuations in absorbed dose. The method is applied to the ground controls of UVPROMs flown on MPTB. These procedures can be used to screen devices for flight parts. Power-law dependence between the rate of electrons leaving the floating gate and the absorbed dose is observed, and it may explain the SEU immunity observed in EPROM memory cells flown in space.

SEE and TID of emerging non-volatile memories

We report on the SEE and TID (total ionizing dose) tests of higher density flash memories. Stand-by currents and functionality tests were used to characterize the response to radiation effects. Single event functional interrupt (SEFI) errors were observed indicating upsets from complex control circuitry.

Sensitivity to LET and Test Conditions for SEE Testing of Power MOSFETs

The results of recent Single Event Gate Rupture and Single Event Burnout testing on power MOSFETS are presented. The recent test data show a considerable drop in failure voltage in comparison to manufacturer data for device ratings over 130V. The effect of range is considered to account for this difference. The methods and practices for testing and data analyses that need to be used for adequate SEE testing of power MOSFETs are also presented. I. INTRODUCTION any space applications are demanding more power and higher voltages. Unfortunately, the technology behind high blocking voltages in discrete devices is susceptible to radiation effects. The large feature sizes and low-doped regions of silicon are the underlying liable areas of these devices to radiation. The application of power devices can be especially stressful when power or voltage requirements are demanding, or the mission environment is hostile. Most power solutions for design approaches in space employ the vertical power MOSFET, but these devices present limitations and trade challenges to projects that require high speed or very large power for high current applications. This work presents the results from various testing of power MOSFETs with rigorous test conditions. This study aims to refine the methodology for adequate hardness assurance of power MOSFETs for space missions.

Microdose analysis of ion strikes on SRAM cells

A method of measuring the effect from exposure to highly localized ionizing radiation on microstructures is described. The voltage at which a commercial SRAM cell cannot hold a programmed state changes with microdose. The microdose distribution across the array, in addition to the analysis of the occurrence of anomalous shifts in operating bias due to rare, large energy-deposition events is studied. The effect of multiple hits on a SRAM cell is presented. A general theory on multiple hits from which basic device parameters can be extracted is presented. SPICE, as well as analysis of basic device physics, is used to analyze the damage to individual transistors and the response of a SRAM cell.