MOS devices are susceptible to damage by ionizing radiation due to charge buildup in gate, field and SOI buried oxides. Under positive bias holes created in the gate oxide will transport to the 2 / SiO Si interface creating oxide-trapped charge. As a result of hole transport and trapping, hydrogen is liberated in the oxide which can create interface-trapped charge. The trapped charge will affect the threshold voltage and degrade the channel mobility. Neutralization of oxidetrapped charge by electron tunneling from the silicon and by thermal emission can take place over long periods of time. Neutralization of interface-trapped charge is not observed at room temperature. Analytical models are developed that account for the principal effects of total dose in MOS devices under different gate bias. The intent is to obtain closed-form solutions that can be used in circuit simulation. Expressions are derived for the aging effects of very low dose rate radiation over long time periods.
An analytical capability is being developed that can be used to predict the effect of corrosion on the performance of electrical circuits and systems. The availability of this "toolset" will dramatically improve our ability to influence device and circuit design, address and remediate field occurrences, and determine real limits for circuit service life. In pursuit of this objective, we have defined and adopted an iterative, statistical-based, top-down approach that will permit very formidable and real obstacles related to both the development and use of the toolset to be resolved as effectively as possible. An important component of this approach is the direct incorporation of expert opinion. Some of the complicating factors to be addressed involve the code/model complexity, the existence of large number of possible degradation processes, and an incompatibility between the length scales associated with device dimensions and the corrosion processes. Two of the key aspects of the desired predictive toolset are (1) a direct linkage of an electrical-system performance model with mechanistic-based, deterministic corrosion models, and (2) the explicit incorporation of a computational framework to quantify the effects of non-deterministic parameters (uncertainty). The selected approach and key elements of the toolset are first described in this paper. These descriptions are followed by some examples of how this toolset development process is being implemented.-4 -
The requirements in modeling and simulation are driven by two fundamental changes in the nuclear weapons landscape: (1) The Comprehensive Test Ban Treaty and (2) The Stockpile Life Extension Program which extends weapon lifetimes well beyond their originally anticipated field lifetimes. The move from confidence based on nuclear testing to confidence based on predictive simulation forces a profound change in the performance asked of codes. The scope of this document is to improve the confidence in the computational results by demonstration and documentation of the predictive capability of electrical circuit codes and the underlying conceptual, mathematical and numerical models as applied to a specific stockpile driver. This document describes the High Performance Electrical Modeling and Simulation software normal environment Verification and Validation Plan.5
This document describes the High Performance Electrical Modeling and Simulation (HPEMS) Global Verification Test Suite (VERTS). The VERTS is a regression test suite used for verification of the electrical circuit simulation codes currently being developed by the HPEMS code development team. This document contains descriptions of the Tier I test cases.
tronic Simulator has been written to support, in a rigorous manner, the simulation needs of the Sandia National Laboratories electrical designers. As such, the develfollowing areas: opment has focused on improving the capability over the current state-of-the-art in the W Capability to solve extremely large circuit problems by supporting large-scale parallel computing platforms (up to thousands of processors). Note that this includes support for most popular parallel and serial computers.Improved performance for all numerical kernels (e.g., time integrator, nonlinear and linear solvers) through state-of-the-art algorithms and novel techniques.W A client-server or multi-tiered operating model wherein the numerical kernel can operate independently of the graphical user interface (GUI).W Object-oriented code design and implementation using modern coding-practices that ensure that the Xyce Parallel Electronic Simulator will be maintainable and extensible far into the future.The code is a parallel code in the most general sense of the phrase -a message passing parallel implementation -which allows it to run efficiently on the widest possible number of computing platforms. These include serial, shared-memory and distributedmemory parallel as well as heterogeneous platforms. Furthermore, careful attention has been paid to the specific nature of circuit-simulation problems to ensure that optimal parallel efficiency is achieved even as the number of processors grows. 3XyceTM User's Guide specific to the needs of Sandia, to the code. To this end, the device package in the Another feature required by designers is the ability to add device models, many Xyce Parallel Electronic Simulator is designed to support a variety of device model and look-up tables. Combined with this flexible interface is an architectural design that inputs. These input formats include standard analytical models, behavioral models greatly simplifies the addition of circuit models.tional Laboratories is in providing a platform for computational research and developOne of the most important contribution Xyce makes to the designers at Sandia Na-"in-house" capability with which both new electrical (e.g., device model development) ment aimed specifically at the needs of the Laboratory With Xyce, Sandia now has an and algorithmic (e.g., faster time-integration methods) research and development can be performed. Furthermore, these capabilities will then be migrated to the end users.
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