Analysis of Single Event Upsets Based on Digital Cameras with Very Small Pixels

Abstract

Digital Imagers provide advantages over ICs when studying Soft Errors (SEUs); when cosmic ray particles hit a pixel, the pixel stores the deposited charge for later readout, providing both their time/area occurrence rate and the area distribution of the charge spread. SEUs are detected within an imager by taking a time sequence of long exposure dark field images, and identifying events that occur only in one image and then disappear. For pixels in the $4-7 \ \mu \mathbf{m}$ range (high end DSLRs) the native noise level is low enough, allowing simple detection of SEUs. However, as pixels shrink to the $1\ \mu \mathbf{m}$ range (cell phone pixels) they become more sensitive to deposited charges (i.e., weaker SEUs) but the background noise rises substantially making it difficult to distinguish between SEUs and noise. Noise in these imagers has a pattern dependent on the pixel's location on the imager. We developed statistical methods that use near neighbor pixels to determine the local noise distribution characteristics and distinguish the SEU events from the noise. We observed that the number of SEU events/area is substantially higher for $1.3 \ \mu \mathbf{m}$ pixels than that experienced by bigger pixels, yet SEUs are still confined to a single pixel indicating that the charge spread is well under $1\ \mu \mathbf{m}$. We also present a statistical analysis of the charge distribution and SEU events and their dependence on the pixel size.