Randomizing gpf patterns inside a single field
If the e-beam system is not working quite right then you might find little glitches (such as tiny gaps) in your pattern. To wash away these errors, you can write the pattern multiple times, much like multi-pass writing to average out stitching errors. But in this case we cannot simply change the field boundaries, because this will not change the fractured shapes inside the field. To randomize the fractured shapes, you can convert the pattern with (say) three different subfield sizes, then recombine the pattern into one gpf file.
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Note that this trick is sometimes useful on the older ebpg 5000, which sometimes has glitchy patterning problems. The new ebpg 5200 does not have these problems. You should NOT waste your time reading this page if you are using the new system. |
Use Beamer (or Freebeam) to create three or four gpf files, each with a different subfield size (eg 4, 3, 2, 1.3 um). Then combine the gpf files with gpfmerge, so that the shapes are randomized. Be SURE to specify the largest subfield first:
gpfmerge biggest.gpf smaller.gpf evensmaller.gpf little.gpf
The resulting gpf file then has the header from the first file, and so the smaller shapes in the other files will not create problems. (ebeam trivia: the ebpg does not use a fixed grid of subfields, and so the entire concept of "subfields" is an artificial restriction inside Beamer.)
After merging the gpf files, the resulting file merged.gpf must be sorted with
gpfsort merged.gpf
to put the fields in a sensible order. By default, gpfsort uses "yellow brick road" sorting, which is probably going to work fine. Alternatively you could specify a path.
Next the file merged_sorted.gpf can be sorted again, so that the shapes inside each field will be exposed in a sensible order. (This is optional). For example,
ybrsort merged_sorted.gpf
will use "yellow brick road" sorting, which works well for snake-like patterns. If your pattern has rings, then you should specify a path for the sorting process; eg
ybrsort -path yourpath.txt merged_sorted.gpf
Type "ybrsort -h" or "gpfsort -h" to see the syntax of the path file. You can use Layout CAD to draw an exposure path, then you can use "extractpath" to create the path file. Type "extractpath -h" to see the syntax.
The resulting file merged_sorted_sorted.gpf can be renamed with
mv merged_sorted_sorted.gpf overlappy.gpf
You would have to use 1/4 (or 1/3) of the normal dose for this exposure. In cview you can confirm that there are overlapping shapes, by hovering the mouse over the pattern and pressing the [ctrl] key:
AFTER ALL THIS you will find that pattern glitches really do get smoothed out. It really works.