Radiation Hardening Testing

SEREEL 2 Laser

The increasing use of microelectronics of ever diminishing feature size has resulted in systems becoming more susceptible to single event effects (SEE). These events are the result of interaction of heavy ions or neutrons. Such particles may arise from natural sources e.g. cosmic or solar particles, or as the result of longer-term weapon effects, or radioactive contamination. SEE range from “soft” errors involving both single and multiple bit upsets in digital devices that corrupt data stored in memory cells (until they are reset), to “hard” catastrophic errors that may lead to a destructive failure of the integrated circuit. The SEREEL 2 laser facility uses very short pulses of light from an ultra fast Ti-Sapphire laser system focused through a microscope objective onto the exposed surface of the device to provide an excellent simulation of single event particle transits in IC’s. This type of facility is potentially an order of magnitude cheaper than testing using conventional ion beams and high-energy neutron beams. It can identify specific susceptible locations over the face of the microchip, which is difficult to achieve with ion beams (micro-beam mapping). The level of controlled generation of SEE in devices using the SEREEL 2 facility also allows ‘closed loop’ type approval testing of error identification and self-recovery in systems.

The SEREEL 2 datasheet can be downloaded here.

Dose rate laser

The total dose and dose rate of X-ray, gamma ray and electron pulses can have an adverse effect on electronic circuits. Cumulative radiation dose causes the generation of electron hole pairs in insulation materials within an electronic device, charge becomes trapped. The trapped charge can then cause the performance of the semiconductor to be changed and the trapped charge effects are then seen as parametric degradation of parts.

X-rays, gamma rays and electrons cause transient electrical responses in semiconductor material in proportion to the incident dose rate. At higher dose rate the generation of electron hole pairs is at rates that influence the behaviour of the circuit function. Thus in very low current applications exposure to low dose rate can have significant behaviour effects and result in the early generation of spurious signals.

At the higher dose rates most parts will start to generate spurious electrical noise and signals; in intense short duration radiation pulses, spurious signals may include command signals, data corruption, change of status, lock-up, and latch-up; however larger devices may conduct so great a current that permanent damage of the part results.

Component testing

The analysis and prediction of radiation effects on electrical/electronic systems requires knowledge of the effects of radiation at component level. The Radiation Effects Group can carry out component trials using radiation effects simulators such as cyclotrons, synchrotrons, linear accelerators, flash X- rays, cobalt-60 sources and pulsed reactors. Procedures for radiation testing embrace internationally recognised test guidelines.

System testing

Performing component assessment/testing and analysis during the design phase minimizes the need for systems testing. When it is necessary to prove/verify system compliance by performing tests, simulators are available to perform a wide range of radiation trials on sub-systems and systems.