1.1.2 DF-ISE

DF-ISE [10] is the file format of the TCAD suite of the ISE software company [11]. As with PIF a binary and an ASCII representation is available although the binary representation is only capable of storing floating point and integer values respectively. Not all of the data are stored in a single file, instead DF-ISE distinguishes several different file types. These file types are

Depending on the application at hand only a sub-set of the data is retrieved from file. Data in a DF-ISE file are organized in a sequence of blocks which in turn can contain other blocks. A restriction of the DF-ISE file format is that a grid file may contain only one global grid that comprises the whole simulation domain. Interfaces between different simulation regions (e.g. semiconductor $ \leftrightarrow$ oxide) must be boundary conforming. Fig. 1.5(b) and Fig. 1.5(a) depict the different conformities.
Figure 1.5: Different interface types. A schematic device with with a simulation domain comprised of four regions is shown. The regions are outlined by red solid lines. The blue dotted lines depict the mesh. Fig. 1.5(a) depicts an interface conforming mesh of the regions. All lines and points on an interface are part of all adjoining meshes. Fig. 1.5(b) depicts the case for a non-conforming mesh. Such grids are not suitable for device or diffusion simulations.
\begin{figure}\centering\subfigure[Conforming grids] {\psfig{file=pics/confGrid,...
...\psfig{file=pics/nonConfGrid, angle=-90, width=0.47\linewidth}}

In the grid depicted in Fig. 1.5(b) some points at the interfaces are only present in one region, as opposed to the grid shown in Fig. 1.5(a), where all points at the interfaces are part of all adjoining regions. This restriction enforces a view of the data that is suitable for device and diffusion simulations but does not very well support topography steps. If several topography steps are to be computed in sequence then the generation of this view after every step clearly imposes an unnecessary overhead on the simulator or the tool that generates the grid based data.

The starting geometry and the photo lithography data (masks) are stored in a layout file. This file is required as input for the process simulator (DIOS).

Access to the data of DF-ISE files is performed via libraries that provide the developer with read and write functions.