480. How does an integrated circuit store so much information?
An integrated circuit is formed by using photographic techniques to sculpt the surface of a silicon crystal, to add chemicals to the silicon, and to deposit layers of other materials on top of the silicon. As part of this sculpting and coating process, a typical computer chip will have tiny memory cells formed on it. These cells usually consist of a tiny pad of aluminum on which a small amount of electric charge can be stored. To store one piece of information, a "bit", on one of these pads, electronic devices called MOSFETs—built right into the silicon surface—are used to control the flow of charge onto the pad. The amount of charge on the pad determines the bit's value. The charge remains on the pad, thus storing the bit, until it's time to recall the bit. At that time, the MOSFETs allow the charge to flow off the pad and into electronic devices that determine what the stored value is.