Submitted to NSREC 2014 1 Abstract— Mean and partial cross section concepts and their connections to multiplicity and statistics of MCU in highly-scaled memories are discussed. It was found that MCU may lead to quasi-linear dependence of cross sections on LET. Index Terms—SEE, SBU, MCU, memory cell, heavy ions, cross section, multiplicity, linear energy transfer. I. INTRODUCTION S process technology advances into deep nanometer ranges, digital memory reliability is becoming a major concern. Highly-scaled digital memories are sus- ceptible to particle-induced single event effect (SEE) because of their low signal charge and noise margin [1]. This circumstance creates new fundamental challenges in terms of modeling, testing, and soft error rate (SER) prediction. One of the main concerns is a problem of the multiple cell upsets (MCUs) in highly scaled memory arrays, CPU registers etc., which are defined as simulta- neous errors in more than one memory cell induced by a single event. The ratio of the MCUs to the single bit up- sets (SBUs) is observed to increase drastically in nano- scaled SRAMs due to physical mechanisms of single- event effects that result in multiple-node charge collec- tion [2]. The total memory area on the chip including inter-cell regions m A is a basic layout parameter. Let SBU N is a number of the single bit-flips after irradiation Manuscript received February 07, 2014. G. I. Zebrev, K. S. Zemtsov, G. S. Sheredeko, M. S. Gorbunov are with the Department of Micro- and Nanoelectronics of National Re- search Nuclear University MEPHI, Moscow, Russia (e-mail: gizebrev@mephi.ru). M. S. Gorbunov, V. E. Shunkov are with Scientific Research Insti- tute of System Analysis, Russian Academy of Sciences, Moscow. V. V. Emeliyanov, R. G. Useinov, A. I. Ozerov are with the Re- search Institute of Scientific Instruments, Lytkarino, Moscow, Russia. V. S. Anashin and A. S. Kozukov are with the JSC Institute of Space Device Engineering, Moscow, Russia. of the chip with heavy ion fluence . Then an experi- mental condition 1 SBU m N A   corresponds to the single bit upset mode with dominance of SBU. This ine- quality means that only a portion of the ions hitting into the memory region area A m leads to upsets. This allows introducing a concept of a separate sensitive volume fol- lowed by a use in standard procedures of soft error rate prediction [3]. An opposite condition 1 SBU m N A   be- comes typical for modern generations of highly scaled integrated memories. Some problems in traditional ap- proach in determination of multiple upset cross sections are noted in [2]. This report aims at discussing of the MCU character- ization and their role in dose-like behavior which was found in highly scaled memories under heavy ion irra- diation. II. PHYSICAL BACKGROUND A. Primitive cell concept Memory ICs are organized as rectangular 2D lattices with the “word lines” running horizontally through the rows, and “bit lines” running vertically connecting all cells in that column together. Following this analogy, a primitive memory cell concept can be defined like the primitive cell in the crystals [4]. More specifically, the smallest area in a memory array, which when repeated in two directions without overlapping, reproduces the com- plete crystal without leaving any void will be referred here as the primitive unit cell. A primitive cell may con- tain in itself one or several bit cells. It should be noted that the choice of the cell shape is not unique, but the cell area cell a is determined exclu- sively by the chip layout and it does not depend on the choice of the primitive cell’s shape. The density of the primitive unit cells per unit area referring here to as N m is defined by the relation 1 m cell Na  and it is also inde- pendent of choice of the primitive cell. Statistics and General Methodology of Multiple Cell Upset Characterization Under Heavy Ion Irradiation Gennady I. Zebrev , Maxim S. Gorbunov, Rustem G. Useinov, Vladimir V. Emeliyanov, Alexander I. Ozerov, Valeriy E. Shunkov, Vasily S. Anashin, Alexander S. Kozukov, Kirill S. Zemtsov, Galina S. Sheredeko A