One in a billion. That is roughly how many foreign atoms Electronic Grade Silicon is allowed to contain, and it is where a processor’s life begins. A Fox News photo feature on how Intel makes a CPU walks through the steps from refined silicon to finished chip.
Silicon is purified in several stages until it hits that grade. A large single crystal is then grown out of the purified melt. The crystal is called an ingot.
Printing the circuits
The wafer is coated with photo resist and exposed to ultraviolet light. Where the light lands, the resist turns soluble. The feature compares the reaction to what happens to camera film when the shutter clicks.
Masks act as stencils, one for each layer of circuit pattern. A lens shrinks the mask image on the way down, so the pattern printed on the wafer is typically four times smaller in each direction than the pattern on the mask.
Hundreds of microprocessors usually share one wafer, but the feature zooms in on a single transistor, a switch that controls the flow of electrical current. Thirty million of them would fit on the head of a pin.
Ions, wiring and packaging
Next, the exposed areas of the wafer are bombarded with ions, a process called ion implantation. The ions change how the silicon in those areas conducts electricity. An electrical field drives them at the surface at more than 185,000 mph.
Metal layers then connect the transistors like wires. The architecture and design teams that define what the processor does decide how the connections run. A chip looks flat to the eye, yet it can hold more than 20 of these layers. Under magnification the result looks like a multi-layered highway system.
The last stage joins three parts into a finished processor. A green substrate forms the electrical and mechanical link to the rest of the PC. A silver heatspreader sits on top, and the cooling device attaches to that.
