Semiconductors

Monday, October 16, 2006

Wafer Fabrication

The first step in wafer production is the fabrication of a silicon single crystal. A small crystal, called the seed crystal, is rotated and slowly withdrawn from the molten hyper-pure silicon to give a cylindrical crystal. The silicon crystal is sliced to obtain thin disks, known as wafers on which chips are made, hundreds at a time, during the following processing. After slicing, the wafers are finely ground, mirror-smooth polished and cleaned.
The most common semiconductor material used today is silicon. In addition to silicon, numerous other materials have been studied, and gallium arsenide (GaAs) is used instead of silicon in some applications at present (e.g. high-frequency devices).
All processes require extremely clean rooms with filtered air to have a low concentration of particles of dust or other contaminants so that a high chip yield can be attained.

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