From Sand to Silicon: How CPUs Are Made Step by Step

Basic Materials

CPU manufacturing starts with silicon, the second most abundant element in the Earth’s crust, extracted from high‑purity quartz sand. Aluminum is used for internal components because its electromigration resistance is superior to copper at modern operating voltages. Additional chemicals are required for various process steps.

Preparation Stage

Silicon is chemically purified to electronic‑grade quality, melted, and poured into large quartz crucibles to form cylindrical ingots (typically 200 mm diameter, with 300 mm variants in advanced fabs). The ingots are sliced into thin wafers, polished to a mirror finish, and inspected for defects.

Photolithography

Each wafer is coated with a photoresist layer, spun to achieve uniform thickness. A mask containing the circuit pattern is exposed to ultraviolet light, hardening the exposed resist. Development removes the soluble regions, leaving a precise pattern that protects underlying silicon during subsequent etching.

Doping (Ion Implantation)

Ion implantation introduces dopant atoms into the exposed silicon regions, altering its conductivity to create n‑type and p‑type areas essential for transistor operation. After implantation, the remaining photoresist is stripped.

Repeating the Process

The sequence of photoresist coating, exposure, development, etching, and doping is repeated multiple times, building up a multilayer three‑dimensional structure. Metal layers (often copper) are deposited and patterned to interconnect transistors, forming the complex circuitry of a modern processor.

Testing and Packaging

Wafers undergo extensive electrical testing to identify functional dies. Defective dies are discarded. Good dies are cut from the wafer, packaged with a substrate and heat spreader, and subjected to final performance and reliability tests that determine their market tier (e.g., Core i7‑975 Extreme vs. lower‑end models).

Final Steps

Packaged CPUs are sorted by performance tier, boxed, and shipped to OEMs or retail channels.