Grades 9–12 · Computing
How do engineers make the tiny patterns on a computer chip?
A computer chip is made by building and shaping thin layers on a wafer. The layers form semiconductor devices and the conductors and insulators connecting them. To place a pattern accurately, manufacturers use lithography: light changes selected parts of a light-sensitive coating called resist.
In the diagramLight patterns a temporary protective coatingOne positive-resist pattern-transfer exampleExposeResist changesDevelopOpenings appearEtchFilm is removedGold: resist • blue: film • gray: waferRepeat aligned layers • not to scale • resist later removed
The coating acts as a temporary patterning material. In the positive-resist example shown here, exposure changes the regions that a developer later removes. The remaining resist covers other areas. An etching process can then remove an underlying film through the openings while covered regions are protected. Light has prepared the pattern; it has not carved a complete computer into bare silicon in one flash.
After this step, the remaining resist can be stripped away. Further operations deposit material, change semiconductor properties or form additional connections. Patterning is repeated, with each new layer aligned to the features already present. The exact order and materials depend on the chip and the layer being made.
The astonishing result comes from precise repetition. Optical systems, controlled chemistry and careful measurement create many copies of small features across a wafer. Inspection catches errors in their size or alignment. Finally, the wafer is divided into individual chips and the working devices are packaged.
About this explanation
Starting knowledge: Understand light-sensitive materials, thin layers, conductors and insulators.
Sources
- ASML — How microchips are made
- ASML — Lithography principles