Area Fill is designed to calculate the area within a window that is covered by metal -- to be more specific, the area that is digitized. Knowing this area can be useful for calculations related to plating and to planarization (CMP).
A window (demo6.gds, layer=8) from -2946,2551 to -2742,2696 um. Metal Density?
The program clips the desired data to the window extents, unionizes the data (so that overlapping polygons do not contribute to an incorrect calculation) and then sums up the area of the results.
The output is written as an ASCII table.
Boolean Layer Operations
Often, the metal pattern on the mask/wafer is defined not by a single GDSII data layer but rather by a combination of layers. Area Fill supports the union of layers, subtraction of one layer from another and reversal of layers.
Tiling Area Calculations
Often one needs to calculate a matrix of local area or densities. For example, one may have a total field area of 25 x 25 mm but needs to know the metal density in 50 um increments. Area Fill has a tile argument that allows the user to define the tile size in X and Y or the number of tiles to use in X and Y.
Same window as above but cut into small tiles. Each tile's area is calculated.
It may be of interest to get a measure of the "spatial frequency" of a particular tile. Two tiles might have the same area fill value but tile (a) might have a single fat rectangle and tile (b) might be composed of many tightly spaced narrow lines.
Both tile (a) and (b) have identical area but are signficantly different.
Area Fill can give an single value indication of the frequency by calculating and reporting the x/y components of the conductor perimeters.
Click on link to see how AreaFill calculates the perimeter along X and Y axis.
Because Area Fill is often used for massive IC layout databases, the program can subdivide the computations using multiple threads. Our users routinely run jobs on 16 CPU's in a 64 bit Linux environment.
Some users might like to produce a density "image." The utility afill2tiff can covert the density (and perimeter) data into a TIFF image.
Memory Footprint for OASIS files
When processing an OASIS file, user should have an idea how much RAM is needed in relation to the OASIS file size and nfork command line option. Details.
Example File and Script
This web page explains the sample batch file we include in our examples folder. Example Detail.
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