Photolithography: definition · Chip Field Guide

Beginner

Printing a pattern onto a chip with light. Light shines through a stencil onto a coating that changes where the light hits it.

Novice

The patterning step repeated for every layer of a chip: coat the wafer with photoresist (a light-sensitive coating), shine light through the mask so the pattern lands on the resist, wash away the exposed or unexposed resist, then etch or add material where the resist has gone, and strip what’s left.

Expert

The smallest printable feature scales as $k_1 \lambda / \mathrm{NA}$ : wavelength $\lambda$ divided by the lens’s numerical aperture NA, times a process factor $k_1$ . Depth of focus shrinks faster, as $\lambda / \mathrm{NA}^2$ . Production machines (scanners) move mask and wafer together past a slit of light, then step to the next chip-sized field on the wafer.