Throughout the 1980s and 1990s, as the semiconductor industry upheld Moore’s law and continuously shrank device feature sizes, the wavelength of the lithography source remained at or below the resolution limit of the minimum feature size. Since 2001, however, the light source has been the 193-nm ArF excimer laser. While the industry has managed to keep up with Moore’s law, shrinking feature sizes without reducing the lithographic wavelength has required extra innovations and steps that increase fabrication time, cost, and complexity. These innovations include immersion lithography and double patterning. Currently, the industry is at the 14-nm technology node. Thus, the minimum feature size is almost an order of magnitude below the exposure wavelength. For the 10-nm node, quadruple patterning has been proposed, causing potentially even more cost, fabrication time, and complexity.
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