The Photolithography is the process which forms the basis of ever-higher
logic densities found in today's computers.ICs are made by layering out the
patterns of metal on top of another.The layout of these patterns, composed
of either conductive or insulating material, builds the transistor that make
up the IC's logic gates.
Adding a new layer first involves covering the die with a photosensitive coating. A mask in the shape of the desired pattern blocks light from from reaching the coating, as shown in the figure.
Chemical processing etches off those sections of the coatoing that are exposed to the light. Logic gates thus build, step by step, in a cycle where another doped layer gets applied, followed by anothe coating, another mask exposure and more etching.