Optical proximity correction

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Image errors without OPC and improvement with OPC structures in the photo mask (scheme)

Optical proximity correction (OPC, English, German for example: optical short-range correction) isa methodin semiconductor technology for the correction or reduction of imaging errors in structures in photolithographic processes. It belongs to the group of resolution enhancement techniques (RET), which are used for structure sizes below the light wavelength (193 nm).


Additional structures

In the photolithographic imaging of a structure with dimensions in the range within and below the wavelength used, as has been the case for several years in microelectronics, imaging errors occur in particular due to wave-optical effects (e.g. diffraction ). The OPC tries to compensate for these effects, such as line end shortening, edge rounding or broadening of neighboring lines, with additional structures on the photo mask. These correction structures, which are also used in several stages, include:

  • extended line ends (ger .: line end extensions to correct) to line reductions
  • partially widened lines ( line end extensions ) for width correction
  • additional lines on the side ( subresolution scattering bar ) for latitude correction
  • T-shaped structures at the line ends ( hammerheads ) to correct rounded edges
  • additional or missing rectangular / square areas ( serifs ) to correct rounded edges
    • additional areas at the convex corners
    • negative (missing) areas at concave corners


Web links

  • Rolf Froböse: RET and OPC masks. In: Sharp thing: Mask technology. tecChannel, February 23, 2004, p. 4 , accessed on January 10, 2010 (picture of a DRAM structure in different stages of manufacture).