Foreign Material
Foreign Material rejection criteria:
(Foreign material is defined as any material that does not originate from the microcircuit or any semiconductor material that is displaced from its original or intended position within the
microcircuit.)
Foreign particle(s) on the surface of the die that is (are) large enough to bridge the narrowest space between unglassivated operating material (metallization, bare silicon, etc...) The
narrowest space will be either (1) between bond pads (window edge to window edge) or (2) bond pad window edge to bare silicon (except for metal that is at the same potential as the
substrate), whichever is smallest.
Foreign material attached to or embedded in the die surface that appears to bridge the active circuit elements including metallization unless verified as only attached but not embedded
by high power dark field illumination.
Liquid droplets, chemical stains, ink, or photoresist on the die surface that appears to bridge any combination of unglassivated metallization or bare surface areas. Ink on the surface of
the die that covers > 25% of a bonding pad area is rejectable.
At left is an example of excess, unetched metal which bridges
across adjacent metal runs.
At right is an example of ink splatter. Because the ink does not bridge unglassivated metal
runs (this area is glassivated) this is not rejectable.
At left is a stringer of photoresist that is bridging across several
metallized and bare silicon areas.
Silicon dust on the surface of the bonding pad that covers > 25% of the bonding pad area.
Additional criteria (CMOS only):
Poly interconnects cannot be bridged by residual poly or foreign material (opaque or otherwise).
Metal interconnects cannot be bridged by residual metal or foreign material (opaque or otherwise).