Chip production today is based on photolithography.
Step : 1
In photolithography a high energy UV-light is shone through a mask onto a slice of silicon covered with a photosensitive film.
The mask describes the parts of the chip and the UV-light will only hit the areas not covered by the mask. When the film is developed, the areas hit by light are removed.
Now the chip has unprotected and protected areas forming a pattern that is the first step to the final components of the chip.
Step : 2
The unprotected areas are processed so their electrical properties change. A new layer of material is added, and the entire process is then repeated to build the circuit, layer by layer.
Step : 3
When all the components have been made and the circuit is complete a layer of metal is added. Just as before, a layer of photosensitive film is applied and exposed through a mask.
However, this time the mask used describes the layout of the wires connecting all the parts of the chip.
Step : 4
The film is developed and the unexposed parts are removed. Next, the metal not protected with film is removed to form the wires.
Finally, the chip is tested and packaged.
When making chips today, a process called "stepping" is often used. On a big wafer of silicon the chips are made one next to the other. The silicon wafer is moved in steps under the mask and the UV-light to expose the wafer. In this way, chip after chip can be made using the same mask each time.
