The best computer chips used presently can hold around 40 million transistors, each measuring around a micrometer (one-thousandth of a millimeter) or less. This is electronics on a microscale, and it is done using what is called a top-down approach. It involves taking material, usually silicon, and slicing it up into many wafers. Patterns (circuits consisting of many transistors) are drawn on light-sensitive films on the surface of each wafer. Using a light source, the unwanted material between the circuits is etched away with acid. The result is a finished product. This manufacturing approach is called top down because you start with something large, and then cut it down to a product you want. Most traditional chip manufacturers use top-down processes.
However, nanotechnology researchers are also looking at another completely new way of manufacturing transistors. The new way requires a bottom-up approach. In this process, molecules are created on the surface of a chip allowing the molecules to self-assemble into larger structures used to make transistors.
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