A novel local illumination scheme for optical lithography is proposed. It is based on the excitation of a surface plasmon on a metal film incorporated into a polymer light coupling mask for contact lithography. The electromagnetic field associated with the surface plasmon generates illumination volumes in the photoresist which are not limited by the diffraction (or Rayleigh) limit. Computer simulations indicate that the replication of 20 nm features using 630 nm illumination wavelength can be achieved with this technique. (C) 2003 Elsevier Science B.V. All rights reserved.