The evolution of microchips

Since 1960, the number of elements that can be made into an integrated circuit has doubled every 18 months. The latest generation silicon chips in 1979 contained 29,000 transistors, but by 1996 this number had risen to 5.5 million. As each new generation of silicon chips packs more components into a circuit, electronic devices get smaller. When laptops first became commercially available, they were about the size of a suitcase. Now modern laptops are the size of an A4 notepad and have much larger processing and memory capabilities.

Some silicon chips only have one function. Memory chips in computers, for example, are created solely to store and retrieve information. Other silicon chips are feature rich and act as minicomputers in their own right. They are known as microprocessors or microchips and contain extremely complex integrated circuits.

Microchips can be taught or programmed to perform a variety of activities, including controlling the actions of other pieces of electrical equipment. In many modern cars, for example, microchips monitor engine temperature and pressure and adjust the amount of fuel injected into the engine accordingly. Typical silicon chips measure between five and seven square millimeters and are thin enough to fit through the eye of a needle. Each chip can include thousands of miniature circuits connected by tiny tracks of conductive aluminum, copper, or tungsten.

inside the chip

Pure silicon has a diamond-like crystal structure and is electrically insulating. However, if impurity atoms (dopants), for example phosphorus, are implanted into its crystalline structure, silicon becomes a semiconductor: it conducts small electrical currents. When silicon is doped, it is given a negative or positive charge, and is known as non-p-type silicon, depending on its charge. Transistors, capacitors, and resistors are made by combining stamped sections of this doped silicon with layers of conductive and insulating materials.

Each layer of material is built into particular places on the chip by masking sections of wafer that don’t need to be covered, in the same way that a decorator uses masking tape to protect glass from paint splatters. Integrated circuits include tens of thousands of different elements linked together by circuit tracks. Often at least 50 procedural steps are needed to manufacture a microprocessor, and manufacturing is known as Large Scale Integration (LSI).