The intricate patterns on today's computer chips are made by a technique known as photolithography. First, a film of photosensitive material, or photoresist, is applied onto a silicon wafer. Exposure to a pattern of intense light causes the photoresist to harden into a protective mask. The wafer is then washed in chemical baths, which etches the unprotected areas. This process can be repeated many times to etch complex and tiny circuit patterns onto the silicon wafer.
The limits of photolithography are set by the wavelength of light. By using ultraviolet light and superlenses capable of subwavelength imaging, scientists say they can push the photolithography boundary down to about 20 nanometers. To get beyond that resolution, researchers are investigating plasmonic lenses, illustrated here, that use excited electrons to focus light into even shorter wavelengths; theoretically, this technique could be used to etch circuit features as small as 5 to 10 nanometers.