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
- layout. Layout geometry for patterning operations.
- cell. Cell structures used for three-dimensional solid modeling.
- recursive-tensor. Contain tensor product grids.
- boundary. Contains a boundary description of the simulation
domain.
- grid. Holds an unstructured grid of the simulation domain.
- dataset. This file type holds optional quantities that are
stored on a grid or boundary. A dataset file is only useful in
conjunction with a grid or a boundary file. Only scalar and
vector values are supported.
- property. Holds a material data base which is used by all ISE
tools.
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
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}}
\par\end{figure}](img14.png) |
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.
2003-03-27
