Via

Via is a small vertical plug that joins two conducting sheets, drawn as a cut and the conductors that sandwich it.

A chip is a layer cake. A wire on metal 1 does not meet a wire on metal 2 unless a via stands between them. A missing via is an open that DRC may not catch if both metals are legal. A via that sits too close to an edge fails enclosure. On the drawing the plug is a tiny square, often 0.15 micrometer on a side, between two larger metal covers. A via array of 4 by 4 squares carries more current than a single cut.

Two straps cross. The square at the crossing is the plug that joins them.

A contact is the cousin that joins the first metal down to silicon, to active or to poly. People say “via” for metal-to-metal and “contact” for metal-to-device, then mix the words by Friday. Both need a layer for the cut. Drawing only the cut leaves the factory short. The metals that the plug touches are required too. A cut in empty space is a hole to nowhere.

The plug, the rim, and the sheet are covered in vias and contacts, enclosure, and what a layer is for.