The History of the Integrated Circuit
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“The History of the Integrated Circuit”
In todays world integrated circuits are everywhere we turn. Many of them you will find in computers. For example the microprocessor is an integrated circuit that processes all information in the computer. It keeps track of what keys are pressed and if the mouse has been moved. It counts numbers and runs programs, games and the operating system.
Chip production today is based on photolithography. In photolithography a high energy is shone through a mask onto a slice of silicon covered with 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 the 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.
Just as in building a house, you need a construction plan to construct a chip. The construction plans for the chip are made and tested on a computer. From the construction plans, masks with the circuit pattern are made. Under precisely monitored conditions, a pure silicon crystal is grown. Circuit manufacturing demands the use of crystal with an extremely high grade of perfection.
The silicon is sawed into thin wafers with a diamond saw. The wafers are then polished in a number of steps until their surface has a perfect mirror-like finish. The silicon wafer is covered with a layer of insulating silicon oxide. A covering film of protective material is put on top of the insulating silicon oxide. This material, a bit like the film in any ordinary camera, is sensitive to light.
UV-light is shone through a mask and onto the chip. On the parts of the chip that are hit by light, the protective material breaks apart. The wafer is developed, rinsed and baked. The development process removes the parts of the protective material exposed to light.
The wafer is treated with chemicals in a process called “etching.” This removes the unprotected insulating material, creating a pattern of non-protected silicon wafer parts surrounded by areas protected by silicon oxide.