MICROCHIP FABRICATION occurs as a cycle of steps carried out as many as 20 times. Many chips are made simultaneously on a silicon wafer, to which has been applied a light-sensitive coating.

(1). Each cycle starts with a different pattern, which is projected repeatedly onto the wafer
(2). In each place where the image falls, a chip is made. The photosensitive coating is removed
(3) ,and the light-exposed areas are etched by gases
(4). These areas are then showered with ions (or "doped"), creating transistors
(5). The transistors are then connected as successive cycles add layers of metal and insulator
(6).
 

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