Soft Errors in Advanced Computer Systems

摘要

AS THE DIMENSIONS and operating voltages of computer electronics shrink to satisfy consumers' insatiable demand for higher density, greater functionality, and lower power consumption, sensitivity to radiation increases dramatically. In terrestrial applications, the predominant radiation issue is the soft error, whereby a single radiation event causes a data bit stored in a device to be corrupted until new data is written to that device. In the past two decades, researchers have discovered three key radiation mechanisms that cause soft errors in semiconductor devices at terrestrial altitudes. In the late 1970s, alpha particles emitted by trace uranium and thorium impurities in packaging materials proved to be the dominant cause of soft errors in DRAM devices. During the same era, researchers showed that high-energy (more than 1 million electron volts, or MeV) neutrons from cosmic radiation could induce soft errors in semiconductor devices via the secondary ions produced by the neutron reactions with silicon nuclei. In the mid-1990s, high-energy cosmic radiation proved to be the dominant source of soft errors in DRAM devices. Finally, researchers identified a third soft-error mechanism, induced by low-energy cosmic neutron interactions with the isotope boron-10 (~(10)B) in IC materials, specifically in borophosphosilicate glass (BPSG), used widely to form insulator layers in IC manufacturing. This recently proved to be the dominant source of soft errors in 0.25-and 0.18-(mu)m SRAM fabricated with BPSG.