Oxide layer
The thin, glass-like film of silicon dioxide that forms on silicon when it is heated. Impervious to impurities and electrically insulating, it became the foundation of chip manufacturing.
In the mid-1950s Carl Frosch and Lincoln Derick at Bell Labs found that the oxide on a silicon surface blocks impurities, and that opening a window in it lets impurities in only beneath the window[1]. In other words, what gets built where can be specified by the pattern in the film.
The film plays several roles: a protective skin over the devices, an insulator between wires, and the insulating layer under the gate of a MOS transistor. Being able to grow such a good oxide is a large part of why silicon, not germanium, came to dominate. Once scaling thinned the film to a few atoms it began to leak current, and in 2007 a different material replaced it under the gate.
Related terms
- MOS transistorA transistor built from a metal electrode, an oxide layer and a semiconductor, in which a voltage on the electrode alone opens and closes the channel. Most of today's chips are made of these.
- Integrated circuitA circuit in which transistors and other components, together with the wiring between them, are all built into a single piece of semiconductor — a chip.
- Gate dielectricThe thin insulating film between the gate electrode and the channel of a MOS transistor. The gate's voltage acts through this film to open and close the channel.