A 4-Mb Non-volatile Chalcogenide Random Access Memory designed for space applications: Project status update

BAE Systems, under contract to the US Air Force Research Labs, has been developing a 4Mb Non-Volatile Chalcogenide Random Access Memory (C-RAM¿) optimized for the radiation environments encountered in spacecraft applications. C-RAM is a phase change memory with a unique combination of features that collectively provide a high-density, low-power, non-volatile memory solution that is radiation hardened and meets rigorous reliability requirements. The device is now undergoing QML qualification in preparation for being flight production ready in early 2009. Flight qualified C- RAM will serve the critical need for rad hard non-volatile RAM in strategic space and military applications. Initial space radiation effects testing (heavy ion induced upset rates) demonstrate the robust nature of the device. No memory cell upsets were recorded and the majority of the observed upsets were soft errors (SE) induced in the sense amp circuits which are easily correctable with common error correcting code (ECC) algorithms. During the product development phase potential failure mechanisms associated with phase change memories such as proximity disturbs and drill-in effects were evaluated to determine whether they were legitimate concerns for C-RAM. These tests and other tests involving second order radiation effects, such as the effect of heavy ion radiation exposure on data retention lifetime were conducted. The results of these investigations further demonstrate the full capacity of the product technology. This paper will describe the C-RAM design and operation, and the results of the test and characterization of C-RAM devices.