Sand is an incredibly simple substance, while there is little in the world that is as complex as a computer chip. But simple silicon elements in the sand are the beginning point for the creation of integrated circuits which power all things today, like supercomputers to mobile phones and microwave ovens.
Turning sand into small devices with millions of components is a remarkable science and engineering achievement that seemed impossible when transistors were discovered at Bell Labs in 1947.
Silicon is a natural semiconductor. In some circumstances, it conducts electricity; in others, it behaves as an insulator. The electrical properties of silicon can be changed by the addition of impurities, a method known as ‘doping’. These properties make it the perfect material for producing transistors, which are basic devices that amplify electrical signals.
Several types of microchips are made today. A microprocessor is a logic chip that calculates on most commercial computers. A memory chip stores information. The digital signal processor converts between analog and digital signals and specific integrated circuits are special-purpose chips used in things such as cars and equipment.
Chips made at a multimillion-dollar fabrication plant called fab. Fabs melts and polish sand to produce 99.9% ingots of pure single crystal silicon. Chainsaws slice ingots into dime-sized wafers of a few inches in diameter. Wafers are given a clean and polish and each is used to build several chips. This takes place in a and “clean room” setting, where many precautions are taken to avoid contamination of dust and any other foreign substances. For the ultimate in ultrasonic cleaning, get a Large Ultrasonic Cleaner from https://www.hilsonic.co.uk/
Non-conductor silicon dioxide layers are grown or stored on the surface of the silicon wafer, and the layer is covered with photosensitive chemicals called photoresist.
Photoresis is exposed to ultraviolet light, which is irradiated through a patterned plate, which toughens the area exposed to light. Areas that have not been exposed are etched with a hot gas to reveal the base of silicon dioxide below. The base and the silicon layer below are further engraved to varying depths.
The photoresis that is hardened by the photolithography process is then stripped off, leaving a 3-D landscape on the chip that replicates the circuit design contained in the mask. The conductivity of specific parts of the chip can also be changed by doping them with chemicals in a heated and pressured environment. The process of photolithography can be followed by lots more etching and doping, hundreds of times on the same microchip, giving a much more complex circuit at every stage.
To make a connecting line between components carved into the chip, the entire chip is thinly coated with metal, normally aluminium and the etching method is used again to take away everything except the narrow conductive path. Sometimes several layers of conductor, separated by a glass insulator, are placed.
Each chip on the wafer is tested for correct performance and then separated from other chips on the wafer by a saw. The chips are well placed into a support package that allows them to be connected to the circuit board, and any chips that aren’t perfect are marked out and disposed of.
