When Jack Kilby invented the integrated circuit in 1958, he had no notion that microchips would one day become foundational to our everyday lives. Today, everything from mobile phones to microwaves runs under the direction of integrated circuits.
Microchips are manufactured in fabrication facilities (known in the industry as ‘fabs’). Although the manufacturing process varies depending on the purpose and complexity of the item, it typically involves the following steps.
Refining the Silicon
Silicon, the basic elemental building in sand, is the starting point for making integrating circuits. Silicon is a semiconductor, meaning it conducts electricity in some circumstances and acts as an insulator in others; this property of ‘on/off’ conductivity makes it the perfect material for transistors.
Transistors are simple devices used to amplify electrical signals or act as switches that control the flow of electricity. Multiple transistors can work in combination to represent the Boolean operators “and”, “or” and “not”, which form the basic computer operating language.
However, silicon is only useable in microchip manufacturing in its purest form. Therefore, fabrication facilities must first refine the silicon sand to produce 99.9% pure silicon ingots. The manufacturers heat silicon to a melting point, then plant a pure silicon ‘seed’ into the molten mixture. The molten silicon forms a chemical bond to the seed and mimics its properties. The resulting ingot pulled from the mixture has the same characteristics as the perfect seed and can be used in manufacturing circuitry.
Forming Silicon Wafers
The pure silicon ingots are then slice into ‘wafers’ of a specific thickness and diameter. Typically, the wafers are cut to the thickness of a dime and a diameter of 8 to 12 inches. These wafers are then polished. Each wafer can be used to build multiple microchips.
Depositing Conducting and Non-Conducting Layers
Each chip is covered in alternating layers of conducting and non-conducting material. The first layer, a non-conducting film, is deposited directly onto the silicon base. The number and order of subsequent layers varies depending on the chip being produced.
Individual layers are overlaid with a photosensitive chemical called photoresist, which creates a mask that covers certain areas and exposes others. The exposed areas can be etched to varying depths to create a complex landscape of circuit pathways.
Layers of metal are deposited to create conducting paths between the etched components. These metal film layers are created using deposition processes such as radio frequency (RF) magnetron sputtering. RF magnetron sputtering can be used to produce extremely thin metal films such as aluminum, silicon or tantalum.
Once the steps are complete, the manufacturer deposits a final protective layer over the whole of the chip.