3.1.1 PIF-Libraries

The two-dimensional version of Minimos-NT was based on the PIF (Profile Interchange Format) [75] file format which was introduced by Duvall in 1988. PIF is a hierarchical file format which has been designed to allow the storage of hierarchically structured data used in TCAD applications. Nevertheless, the storage format of PIF files is not defined in detail resulting in several valid formats used for different applications. Therefore, Minimos-NT uses a special PIF definition. This format is well suited for the description of devices of any dimensionality. The complete access to PIF files is accomplished by libraries [107] called PIF-Libraries.

The Geometry2DSupport library (G2S) supports simple functions for reading the geometry of a device from a PIF file, for performing some small simplifications, for analyzing the geometry, and for writing the geometry back to an output file. The most important functions used by Minimos-NT are g2sReadGeometry, g2sWriteGeometry and functions to analyze the geometry of a device. g2sReadGeometry is used to read the geometry and to initialize several handles. These handles are mainly used to initialize and to read the attributes stored in a PIF file. g2sWriteGeometry writes the geometry information back to the output file. Many other Geometry2DSupport library calls are used to build up the internal grid representation.

The GeometryAttributeSupport library (GAS) allows access to all quantities stored in a PIF file. It supports functions to read the quantities from the PIF file, to manipulate them, to create and delete quantities, and to write them back to the output file. The handle returned by g2sReadGeometry of the Geometry2DSupport library is used to initialize the AttributeSupport library. Both libraries are closely related as the Geometry2DSupport library stores the geometry the quantities are defined on.

The main purpose of the GridSupport library (GRS) is to support triangular and ortho-product grids and to offer manipulation functions as for interpolation of quantities defined on those grids.

All these three libraries are based on the PIFApplicationInterface library (PAI) which forms the lowest level. PAI is split into several layers with interfaces to each other. Each layer communicates only with its underlying layer. PAI stores an internal representation of PIF files read. The application interface consists of functions which allow access to the real files providing a caching algorithm to minimize disc access. Minimos-NT used these libraries to read and write the geometry- and grid-information and all necessary attributes from and to PIF file.

The general advantages of these libraries are:

• The PIF is well established.
• A set of functions exists which allows to query and manipulate data which emerge in TCAD applications.
• A powerful two-dimensional visualization tool called xpif2d exists which is used to analyze simulation results and geometries as well.
• Both an ASCII format and a more efficient binary format exist.

Some general disadvantages of these libraries are:

• The number of devices and the maximum size of a PIF file is limited. These limits are binary coded within the libraries. If the number of devices is increased, the maximum file size is reduced. Therefore, complex mixed mode simulations with many big devices are impossible.
• The handling of these libraries and the handling of attributes is rather awkward.