High Quality Content by WIKIPEDIA articles! Elements of the circuit to be created on the IC are reproduced in a pattern of transparent and opaque areas on the surface of a quartz plate called a photomask or reticle. The stepper passes light through the reticle, forming an image of the reticle pattern. The image is focused and reduced by a lens, and projected onto the surface of a silicon wafer that is coated with a photosensitive material called photoresist. After exposure in the stepper, the coated wafer is developed like photographic film, causing the photoresist to dissolve in certain areas according to the amount of light the areas received during exposure. These areas of photoresist and no photoresist reproduce the pattern on the reticle. The developed wafer is then exposed to acids or other chemicals. The acid etches away the silicon in the parts of the wafer that are no longer protected by the photoresist coating. The other chemicals are used to change the electrical characteristics of the silicon in the bare areas.

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