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All nanometer sized electronic components are made using a process called lithography. Alois Senefelder of Munich discovered the basic principle of lithography, “printing on stone”, around 1798. It is based upon the notion that oil and water do not mix. Photolithography involves using energy (e.g., light or electrons) to change the solubility of a material. Photolithography literally means light-stone-writing in Greek. An image can be produced on a surface by drawing with light or electrons much the same way that you might scratch away the crayon on a scratch board.
In nanotechnology we use photolithography to transfer a pattern from a ‘mask’ to a surface. We apply a special chemical called ‘photoresist’, which is sensitive to light, onto the surface that we want to pattern. The mask is a stencil which allows the light energy to pass through only certain regions. So a pattern on a mask can be transferred to a surface by passing light or electrons through the mask. When the light or the electrons reach the photoresist on the surface, the solubility of the photoresist changes making it easier or harder to wash away. What is left after washing is the three-dimensional pattern that was originally on the mask. It is transferred to the photoresist. Scientists use photolithography to make computer chips and other devices that have very small features, as small as 100 nanometers.

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