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Bandwidth, Illumination The range of wavelengths that is used to illuminate the mask, and thus to expose the resist.
Example: The illumination bandwidth for a typical g-line stepper is about 10nm FWHM.
BARC see Bottom Antireflective Coating
Bias see Mask Biasing
Binary Mask A mask made up of opaque and transparent regions (for example, one composed of chrome and glass) such that the transmittance of the mask is either 0 or 1. Also called a binary intensity mask.
Example: The needed resolution was not obtained using a conventional binary mask.
Birefringence A somewhat rare property of some materials (usually crystals) where the refractive index of the material is a function of the polarization of the light passing through the material.
Example: The discovery that calcium fluoride exhibits significant intrinsic birefringence caused considerable consternation during the development of 157-nm lithography.
Bleaching, Photoresist The decrease in optical absorption of a photoresist due to the chemical changes that occur upon exposure to light.
Example: Without photoresist bleaching, this resist could not be used effectively at thicknesses greater than about 2 micrometers.
Bossung Curves see Focus-Exposure Matrix (named after John Bossung, the engineer who first published these curves.)
Bottom Antireflective Coating (BARC) An antireflective coating placed just below the photoresist to reduce reflections from the substrate.
Example: The use of a bottom antireflective coating not only reduced the swing curve, but also nearly eliminated the effects of reflective notching.