chemicals and light. Silicon, the second most abundant element on

Earth, is used extensively in transistors, integrated circuits, photoelectric devices, and other electronic devices. A pure crystal of silicon does not conduct electricity unless traces of other substances are diffused or doped onto it. Therefore silicon must be manufactured in a specific way in order for it to yield electrons for a current.

All manufacturing of silicon takes place in a "clean room" which is an area where each one foot cube of air must contain fewer than 1000 tiny specks of dust and zero humidity. The temperature is maintained at a constant 68 degrees Fahrenheit and all workers have to wear coats, gloves, masks, and overshoes. This is necessary because even one dust particle or water droplet can ruin a batch of chip production.

The base of the chip is next doped with small traces of boron. First the silicon base is coated with a layer of insulating silicon dioxide and photoresist, a light-sensitive material. This hardens only where ultraviolet light, projected through a mask, strikes it. The chip is immersed in solvent to wash away the soft resist shielded by the mask. Hot gases than etch away most of the dioxide, leaving a thin layer for insulation, and the rest of the resist is removed.

A layer of conducting polysilicon is now deposited, as well as a new layer of resist. A second exposure through a mask is made, and after washing the chip with solvent an L-shaped pattern remains on the chip. Etching removes the polysilicon not shielded by the resist as well as a thin layer of dioxide, exposing two wells of the silicon base. The rest of the resist is then removed, so the gate rises above the wells. Doping transforms the two wells of p-type into n-type silicon, which carri

Some common words found in the essay are:
, crystal silicon, rest resist removed, thin layer, resist removed, n-type silicon, silicon base, rest resist, manufacturing silicon,
Approximate Word count = 649
Approximate Pages = 3 (250 words per page double spaced)