A wafer is a thin slice of semiconductor material, typically high-purity single-crystal silicon, that serves as the substrate for microelectronic devices. It's the foundational canvas upon which integrated circuits are fabricated through sophisticated manufacturing processes. Standard wafer diameters have evolved from 1 inch to the current mainstream 12-inch (300mm), with 18-inch wafers under development.

Wafer production begins with ultra-purification of silicon to 99.9999999% (9N) purity. Using the Czochralski method, cylindrical single-crystal silicon ingots are grown, then sliced into 0.5-0.7mm thick discs and polished to achieve atomic-level surface flatness. Even nanometer-scale defects can significantly impact chip yield.

In semiconductor fabs, wafers undergo hundreds of processing steps including photolithography, etching, ion implantation, and thin-film deposition to build multilayer circuitry. A 12-inch wafer can yield hundreds of chips, with more advanced process nodes (e.g., 7nm, 5nm) enabling higher integration density. After processing, wafers are diced into individual dies for testing and packaging.

Wafer technology directly determines semiconductor capabilities. Increasing wafer sizes and process advancements continue to drive Moore's Law. While China is rapidly building 12-inch wafer fabs, high-end silicon wafers still rely on imports, making breakthroughs in wafer manufacturing crucial for semiconductor self-sufficiency.