Density window
Beginner
A square patch of the chip in which the factory checks how much of the area is covered with metal.
Novice
A square of fixed size over which a density rule is measured, such as “metal must cover 20% to 80% of every 50 µm window.” The checker steps the window across the whole chip, often in overlapping steps.
Expert
Checked over a fixed dissection: windows of size stepped by , so each window covers tiles. A larger comes closer to checking every possible window position, at more runtime.
Explained in GDS & tapeout (Design Flow).
See also: Metal fill (density fill), Chemical-mechanical polishing (CMP).