The microchip or silicon chip has completely changed the colour of the electronic world by providing a new direction to it. It has led to the invention of electronic calculators, personal computers, digital watches, microwave ovens etc.
The silicon chips are tiny crystals of silicon which contain large number of electronic components. Silicon is the most abundant element on earth as the crust of the earth is largely made of silicon. But silicon is not found in a free state as it is always combined with one or more additional elements. In one sq. cm. chip, about one million electronic components can be squeezed. The size of a chip is smaller than our finger tips. They can be made to carry very small electrical circuits, called microcircuits. These are used in transistor radios, digital watches, calculators and computers. They can be used in small electronic devices as the chips are very small.
But how is silicon chips made? Silicon chips are made from a single crystal of silicon. Thin wafers of about 0.5 mm thick are sliced from a single crystal. One side of each wafer is first polished and then oxidized in a furnace: The disc is covered with a layer of photo resist material and then exposed to ultraviolet light through the clear sections of a mask. A light sensitive coating is developed and the exposed areas are dissolved away by the solvent. Unexposed areas are not affected so a pattern remains identical to the mask. The exposed areas are etched in hydrofluoric acid. Another solvent removes the resist. In a furnace, the wafer is exposed to chemicals which penetrate the silicon through the oxide gap to make transistors. The process is repeated several times. The wafer is coated with aluminium and a final layer of metals connects the components together. After careful inspection, chips are selected and released for use.
Nowadays microchips are being used in electronic sewing machines, washing machines, word processors, and so on.