LineCommand

LINE

line - Specify a mesh line location

Synopsis

line

(x | y | z)
location = <value>
[spacing = <value>]
[tag = <string>]

Description

This statement is used to specify the position and spacing of mesh lines. All line statements should come before region statements, which should in turn be followed by an initialize statement.

Only flat structures can be specified with line and region statements.

FLOO* has the following coordinate system. X is the direction normal to the wafer with positive x oriented into the bulk of wafer. Y is perpindicular to the x direction and lies along the wafer surface. Y is the normal masking direction. This is not the same as SUPREM-IV or PISCES-II. This was done to simplify computation of one- and two-dimensional structures. In both one and two dimensions, X is vertical and positive into the wafer.

x | y | z

This allows specification of the orientation of the mesh line. Specifying x places a mesh line at a constant x value. A series of line x commands would be specify the vertical grid locations during the simulation

location

The location along the chosen axis, in microns.

spacing

The local grid spacing, in microns. Each mesh line has a characteristic desired spacing. Lines will be graded from one spacing to the next over the interval. The default is a spacing equal to the largest interval between the neighboring lines. The algorithm used in the same employed in SUPREM-IV.

tag

Lines can be labeled for later reference by region statements. The label is any word you like.

Examples

line x loc=0 spa=0.02 tag=surf
line x loc=3 spa=0.5 tag=back
line y loc=0 spa=1 tag=left
line y loc=1 spa=0.1
line y loc=2 spa=1 tag=right

There are 3 user-specified y lines and 2 user x lines. Taking the y lines for illustration, there is finer spacing in the center than at the edges. After processing, FLOO* produces a mesh with x lines at 0.0, 0.42, 0.69, 0.88, 1.0, 1.12, 1.31, 1.58, 2.0. Around the center, the spacing is 0.12, approximately what was requested. At the edge, the spacing is 0.42, because that was as coarse as it could get without having an interval ratio greater than 1.5. If the interval ratio was allowed to be 9, say, then we would have got one interval of 0.9 and one interval of 0.1 on each side. In this example, specifying a spacing of 1 at the edges was redundant, because that's what the spacing of the user lines was anyway.

Bugs and Missing Features

It's hard to guess how many lines are going to be generated in each interval.

Coarse spacings are sometimes rounded down by the smoothing algorithm in an undesirable way, creating too many grid points.