Metal

Metal is a conducting film in the process stack, drawn as shapes that become wires, shields, and landings after the factory plates or cuts it.

Most of the visible drawing is metal after the first few device sheets. Metal 1 is usually the finest. Upper metals grow thicker and wider. A 0.14 micrometer minimum on metal 1 might become 0.4 micrometer on metal 4. Power likes the thick layers. Signals start low and climb with via stacks. On screen the sheets are colored rectangles named M1, M2, and M3. Turn the other sheets off and the chip still looks busy. A pin lives on a metal. A pad is a large metal with a passivation opening.

Two straps of conducting film, one turning a corner, before any factory step plates them.

On a board the cousin is copper. In the file, metal is a layer number, not a photograph of shine. Width and spacing rules are written per metal. A wire drawn on the wrong metal because the color was pretty sits on the wrong process step. Color is local to the editor. The number is the process step, which is why what a layer is for starts with the sheet and not the paint. How two metals meet is vias and contacts. The board cousin of the same stack is a PCB stackup.