To characterize and understand the single event response of an SRAM cell, a large simulation matrix is designed. The matrix includes various ion-strike locations, linear energy transfer (LET) values, and incident ion angles, resulting in more than 100 simulations.
Figure 4 shows an example of a matrix of hit locations, where X indicates the area on the surface of the structure where an ion will impact the silicon.
«Fig. 4»Top view of six-transistor SRAM cell; X indicates the locations where heavy ions with varying LETs will strike the device.
The Sentaurus Workbench software package allows us to set up these complex matrices easily, to interface with the ACCRE computing cluster, and to utilize fully the available processing power. This permits many jobs to be run simultaneously, rather than one after another, greatly enhancing data collection and simulation performance.
Currently, all of the nodes on ACCRE consist of dual processors. Parallelization of the device solver allows the use of both processors and all the memory on a node, reducing the time for each simulation by up to 41%. Accounting for hit location, incident angle, ion species, and energy, characterization of the single event response of the SRAM cell may involve more than 100 simulations that take 4–5 days each to complete on a single processor; the time savings obtained by using the multiprocessor capability are significant.
Conclusion
The high level of integration associated with scaled devices requires multiple-device 3D simulations to characterize single event effects. Such simulation capabilities allow the prediction of the performance of design variants operating in different radiation environments. However, these simulations are very complicated and can demand significant amounts of computing power. TCAD Sentaurus Version Z-2007.03 gives users the ability to design and build these cells, and provides the flexibility needed to integrate into a high-performance computing cluster environment such as ACCRE, for a comprehensive characterization of complex physical phenomena such as single event effects.
About ISDE
ISDE is the applied research division of the Vanderbilt University School of Engineering Radiation Effects Group, which is the largest program of its kind in the United States. ISDE studies radiation effects in microelectronics equipment by leveraging a combination of experienced people, custom-developed software, commercially available software, and the Vanderbilt University ACCRE highperformance computing facility.
References
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