Geography Of Computers

Making Silicon

The first topic I will cover in my blog is silicon chips. I will first be covering how silicon chips are made for computers.

Silicon is the 2nd most abundant material on earth but only found in bonded states and I'm going to explain how it is purified.

MAKING SAND INTO SILICON

Sand has silica (silicon dioxide). That is why it is the starting material for making silicon chips. But no ordinary sand from the beach will work. They use a purer form of sand called silica sand. This sand is gotten from quarries.

The sand needs further purification by removing the oxygen from the silica in order to made silicon. They do this by mixing silica and carbon and put it in a special furnace called the electric arc furnace and heat it till over 2000°C. The oxygen reacts with the the carbon to form carbon dioxide. The silicon then settles to the bottom of the furnace. Next the silicon is treated with oxygen to remove any calcium and aluminium from the silicon. Now the silicon is of a metallurgical grade and is up to 99% pure. This is still not pure another for the silicon chips.

The silicon is ground to a fine dust which is reacted with gaseous hydrogen chloride in a fluidised bed reactor which is heated to 300°C which make a liquid form of silicon called trichlorosilane. The impure material reacts into their chloride which is then removed through a process of fractional distillation. The trichlorosilane is vaporized and reacted with hydrogen gas at 1100°C so they can change it back to silicon. The silicon is poured over an ultra pure silicon rod to make a silicon ingot of electronic grade which is 99.999999% pure.