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| Moore's law, optical lithography and the search for alternatives. Computer chips (and the silicon based transistors within them) are rapidly shrinking according to a predictable formula (by a factor of 4 every 3 years - Moore's Law). According to the Semiconductor Industry Association's extrapolation of formulas such as this one (SIA roadmap), it is expected that the sizes of circuits within our chips will reach the size of only a few atoms in about 20 years. Since almost all of our modern computers are made from silicon semiconductor transistors patterned and carved by light (photolithography), the shrinking of circuits predicted by the SIA may not be the most economical method for the future. An enormous amount of money has been invested in the semiconductor industry in order to consistently shrink and improve our semiconductor electronics. Smaller circuits require less energy, operate more quickly and, of course, take up less space. Thus, Moore's law has been adhered to since computers first became commercially available. However, this simple shrinking of components can not continue for much longer. As transistors such as the Metal-Oxide Semiconductor Field Effect Transistor (MOSFET - one of the primary components used in integrated circuits) is made smaller, both its properties and manufacturing expense change with the scale. Currently, Ultraviolet light is used to create the silicon circuits with a lateral resolution around 200 nm (the wavelength of ultraviolet light). As the circuits shrink below 100 nm new fabrication methods must be created, resulting in increasing costs. Furthermore, once the circuit size reaches only a few nanometers, quantum effects such as tunneling begin to become important, which drastically changes the ability for the computers to function normally. Thus, novel methods for computer chip fabrication have been and are being intensely sought by microchip manufactures. |
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