A. D. Touboul

Dose rate effects in bipolar oxides : Competition between trap filling and recombination

Predicting the low-dose-rate degradation of bipolar technologies is one of the main issues for circuits intended for use in the ionizing-radiation environment of space because of the enhanced low-dose-rate sensitivity (ELDRS). In this letter, ELDRS is shown to be related to competition between trapping and recombination of radiation-induced carriers in the oxide. The presented model is shown to be in good agreement with experimental data. It is also shown that this effect is strongly dependent on the oxide quality.

The Use of a Dose-Rate Switching Technique to Characterize Bipolar Devices

The enhanced radiation sensitivity exhibited at low dose rate by many bipolar devices remains one of the main concerns for spacecraft reliability. As an accelerated test technique, a new approach based on dose-rate switching experiments has been proposed to characterize bipolar devices. The foundations of this approach are detailed and guidelines for its use are given.

Discontinuous ion tracks on silicon oxide on silicon surfaces after grazing-angle heavy ion irradiation

Thin silicon oxide layers on silicon have been characterized by atomic force microscopy before and after swift heavy ion irradiation with 0.63MeV∕u Pb ions at grazing angle of incidence. In this letter, the authors report the observation of extended intermittent tracks at the silicon oxide (SiO2) surface. As a result, this raises the question of the discontinuous energy deposition at the nanometric scale. This experimental overlook is of major interest for nanostructuring and surface nanoprocessing as well as with regard to reliability of electronic components and systems.

Total dose effects on gate controlled lateral PNP bipolar junction transistors

A gate controlled lateral PNP bipolar device has been designed in a commercial BiCMOS process to investigate its sensitivity to radiation-induced degradation. New experimental and simulated results concerning total dose effects are presented. The improved radiation hardness of this device working in its accumulation mode is shown. The influence of the gate potential during irradiation is studied as well as the effect of the gate potential on the degraded current characteristics.

Effects of atmospheric neutrons and natural contamination on advanced microelectronic memories

We have investigated material susceptibilities to atmospheric neutrons by calculating nuclear cross sections for every natural element from carbon to bismuth. The alpha emitters that can be present in microelectronic devices have also been identified. To improve the performance of microelectronic devices, the semiconductor industry has introduced a number of chemical elements in the device process. These elements experience a natural flux of neutrons and can also contain natural radioactive isotopes. In both cases, device reliability can be compromised. We show that, at ground level, the introduction of an element may be more important than the effect of neutrons.

Growth of silicon bump induced by swift heavy ion at the silicon oxide-silicon interface

Thin silicon oxide layers on silicon substrates are investigated by scanning probe microscopy before and after irradiation with 210 MeV Au+ ions. After irradiation and complete chemical etching of the silicon oxide layer, silicon bumps grown on the silicon surface are observed. It is shown that each impinging ion induces one silicon bump at the interface. This observation is consistent with the thermal spike theory. Ion energy loss is transferred to the oxide and induces local melting. Silicon-bump formation is favored when the oxide and oxide-silicon interface are silicon rich.

Testing a Commercial MRAM Under Neutron and Alpha Radiation in Dynamic Mode

Academic and industrial research interest in terrestrial radiation effects of electronic devices has expanded over the last years from avionics and military applications to commercial applications as well. At the same time, the need for faster and more reliable memories has given growth to new memory technologies such as Magnetic (magneto-resistive) Random Access Memories (MRAM), a promising new non-volatile memory technology that will probably replace in the future the current SRAM and FLASH based memories. In this paper, we evaluate the soft error resilience of a commercial toggle MRAM in static and dynamic test mode, under neutron radiation with energies of 25, 50 and 80 MeV as well as under a Californium (Cf-252) alpha source.

Determining Realistic Parameters for the Double Exponential Law that Models Transient Current Pulses

We calculated Single Event Upset (SEU) cross-section as well as the neutron Soft Error Rate (SER) at ground level for three SRAMs (90 nm, 65 nm an 40 nm). For this purpose, we first investigate the transient current pulse induced at each drain electrode, by using the diffusion model for the transient current pulses. Then, we performed the same simulations by replacing each transient current by a simple double exponential law model, for which the parameters were set in order to keep the same fundamental parameters of the diffusion model such as total charge, maximum value of current and its corresponding occurrence time. Our results show a little systematic increase of the cross section while using the double exponential law. Moreover, we showed that only two parameters of the double exponential law are actually required to investigate Single Event Upsets. Finally, we provided for the 90-nm some analytical expression in order to estimate the distribution of parameters that appear in the double exponential law.

Contribution of Latent Defects Induced by High-Energy Heavy Ion Irradiation on the Gate Oxide Breakdown

From annealing and electrical stress experiments performed on irradiated MOS devices, swift energetic ions-induced morphological oxide defects are shown to act as a contributing part of the oxide breakdown occurring during post gate stress, without being possibly electrically detected before the onset of breakdown itself. A reduction of the charge to breakdown and an increase of the radiation-induced leakage current were first observed after irradiation. Then, leakage current has been shown to be fully removable using isochronal annealing while charge to breakdown was not increased back to its initial value.

High-Energy Heavy Ion Irradiation-Induced Structural Modifications: A Potential Physical Understanding of Latent Defects

From annealing experiments performed on both irradiated SiO2-Si structures and MOS devices, swift heavy ions-induced morphological oxide defects are proposed to possibly act as latent defects.