chip

A chip is a single block of material, typically silicon or gallium arsenide, onto which thousands to billions of transistors, resistors, capacitors and other components are fabricated in layers. The finished chip, often just a few millimetres square and under a millimetre thick, is mounted into a package with leads or balls that connect it to a circuit board. The term covers everything from simple logic gates to complex processors, memory devices and application-specific integrated circuits (ASICs).

The chip itself is the product of photolithography. A wafer of silicon, often 200 or 300 millimetres in diameter, is coated with a light-sensitive resist. A mask is used to project circuit patterns onto the resist, which is then developed to expose parts of the underlying material. Through repeated cycles of oxidation, dopant implantation, deposition and etching, the patterns build up into a functional 3D structure. Modern processes operate at feature sizes of 5 nanometres or smaller, meaning individual transistors are vastly smaller than a human cell.

The finished wafer contains dozens or hundreds of identical chips arranged in a grid. Each chip is then separated by sawing, tested, and mounted into a package: plastic or ceramic with metal leads, ball grid arrays (BGAs) with hundreds of solder balls underneath, or flip chips bonded directly to a substrate. The package provides mechanical protection, thermal management and electrical connectivity to the outside world.

Variants and failure modes

Analogue chips amplify or filter signals and are sensitive to noise and temperature drift. Digital chips switch between voltage levels representing 0 and 1, and are more robust to interference but very sensitive to power supply glitches. Memory chips store data and demand precise voltage and timing. Power chips handle large currents and dissipate significant heat; thermal management through heatsinks, thermal vias and substrate materials becomes critical. Defects introduced during fabrication, mechanical stress during mounting, electrostatic discharge (ESD) during handling, or thermal cycling during operation can all render a chip non-functional or cause it to fail prematurely.

The word chip derives from the fact that individual dies are literally chipped away from the wafer. In the early days of integrated circuits in the 1960s, the term distinguished them from discrete components (individual transistors, resistors and capacitors soldered together by hand). Today chip and integrated circuit are used interchangeably, though chip is the colloquial standard across the industry.