| << Chapter < Page | Chapter >> Page > |
| Coupled Method | Uncoupled (sequential) method |
| Generalization of Newton method | Basis of Gummel’s method |
| Large memory required | Memory efficient |
| Converges rapidly | May converge rapidly at low DC bias |
| Initial guess is critical | Converges slowly at large DC bias |
There are three physically-based simulation. These are:
• It is predictive.
• It provides insight.
• It conveniently captures and visualizes theoretical knowledge.
Physically-based simulation is different from empirical modelling. The goal of empirical modelling is to obtain analytic formulae that approximate existing data with good accuracy and minimum complexity. Empirical models provide efficient approximation and interpolation. They do not provide insight, or predictive capabilities, or encapsulation of theoretical knowledge.
Physically-based simulation has become very important for two reasons. One, it is almost always much quicker and cheaper than performing experiments. Two, it provides information that is difficult or impossible to measure.
The drawbacks of physically-based simulation are that all the relevant physics must be incorporated into a simulator, and numerical procedures must be implemented to solve the associated equations. These tasks have been taken care of for users of ATLAS.
Those who use physically-based device simulation tools must specify the problem to be simulated. In ATLAS, specify device simulation problems by defining:
• The physical structure to be simulated.
• The physical models to be used.
• The bias conditions for which electrical characteristics are to be simulated.
7.3. Application of ATLAS.
Figure 7.1. ATLAS INPUTS AND OUTPUTS.
Figure 7.1 shows the types of information that flow in and out of ATLAS. Most ATLAS simulations use two input files. The first input file is a text file that contains commands for ATLAS to execute. The second input file is a structure file that defines the structure that will be simulated.
ATLAS produces three types of output files. The first type of output file is the run-time output, which gives you the progress and the error and warning messages as the simulation proceeds. The second type of output file is the log file, which stores all terminal voltages and currents from the device analysis. The third type of output file is the solution file, which stores 2D and 3D data relating to the values of solution variables within the device at a given bias point.
7.3.1: Modes of Operation
ATLAS is normally used in conjunction with the DECKBUILD run-time environment, which supports both interactive and batch mode operation. We strongly recommend that you always run ATLAS within DECKBUILD. In this section, we present the basic information you need to run ATLAS in DECKBUILD.
7.3.1.1: Interactive Mode With DeckBuild
To start ATLAS in DECKBUILD, type:
deckbuild - as
at the UNIX system command prompt. The command line option, -as , instructs DECKBUILD to start ATLAS as the default simulator.
If you want to start from an existing input file, start DECKBUILD by typing:
deckbuild - as<input filename>
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