"A New Tool for Modeling Single Event Upset Rates Produced by Nuclear Reactions of Space Radiation with Microelectronic Devices"

William J Atkinson and William A Seidler
The Boeing Company


Boeing has developed a tool using the Monte Carlo N-Particle Transport Code (MCNPX) to predict single-event upset (SEU) rates produced by nuclear reactions of space radiation with microelectronic device models. Products of these reactions include neutrons, recoiling ions, and delta rays (high speed electrons). The tool models  angular dependence of all reaction products, the transport of radiations across overlayers to the sensitive silicon volume, complex spatial variation of charge deposition throughout all components of the device, doping of the silicon volume, detailed device geometries (edge effects, isolation trenches, buried oxides), and recoiling ions with atomic number as high as 100.

Application of the tool to space based 4 Mbit SRAM hardened to ~ 1 pC indicated that nuclear reactions alone can produce charge depositions equal to the critical chare of 1 pC when exposed to peak solar flares, 0.6 pC in Galactic Cosmic Rays (GCR), and daily SEU occurrences in peak solar flares. These results are not predicted by off the shelf tools such as the 1996 version of Cosmic Ray Microelectronics Effects (CREME96) that neglect nuclear reactions as a contributor to charge deposition in microelectronic devices. The tool also predicts that neutrons produced in the atmosphere by bombarding space radiations (terrestrial neutrons) produce 12.0 upsets per day at an altitude of 60000 feet and 0.3 upsets per day at ground level in 4 Mbit RAM with a feature size of 85 nm.

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