Chips are mounted on the wafer through a process called photolithography. Under this process, chemicals sensitive to ultraviolet light are used. When exposed to ultraviolet light, they can become “soft” or “hard”. So basically this process consists in blocking the ultraviolet light from the chemicals applied to the wafer using stencils (the masks created by the engineers), removing the “soft” parts, and then repeating the process again with another mask, until the chip is finished.

PhotolithographyFigure 2: How photolithography works.

Of course each mask has a different pattern and they tell how the transistors and wires inside the chip will be manufactured. The numbers of masks used vary depending on the project. A Pentium 4 processor, for example, uses 26 masks.

Let’s see exactly how this process is done.

Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.