Layers upon Layers
The layering and masking processes are repeated, creating windows that allow for connections to be made between the layers.
Atoms of metal are deposited on the wafer, filling the windows. Another masking and etching stage leaves strips of the metal that make the electrical connections.
Roughly 20 layers are connected to form the microprocessor's circuitry in a 3-dimensional structure. The exact number of layers on a wafer depends on the design of the microprocessor.
