Fracture

Fracture is the slicing of drawn outlines into the primitive flashes a plate-writing machine can shoot: trapezoids, rectangles, or beam shots.

One run is broken into rectangles. A thin sliver sits in one of the seams.

A photomask machine does not take a 200-point polygon as finished art. It wants a pile of simple figures, and fracture is that translation. A circle becomes hundreds of trapezoids. All-angle jogs that come from OPC become still more slivers. Write time and cost follow the sliver count. In a mask-prep view a smooth inductor appears as a mosaic of trapezoids. A 10 micrometer circle might become 64 wedges, then twice that number after correction.

E-beam writers fracture the pattern into shots. Optical writers fracture it into the figure set their tool accepts. Either way, vertices have to stay on the grid, or the fracture step invents off-grid junk. Shops quote mask time from fractured figure counts, not from how calm the editor looks. A waveguide bend can cost more than a city of Manhattan rectangles. Ask for a figure report before a plate is blessed. If two fracture runs of the same cell differ by millions of slivers, someone changed the OPC or the grid, not the circuit.

Editing the fractured output does not repair the mask. The next run rebuilds the figures from the design. Fix the source cell, then fracture again.

The accounts are mask fracture in one sitting, what a photomask is, and e-beam writes one shape at a time.