IMAGING PROFILES OF LIGHT-INTENSITY IN THE NEAR-FIELD - APPLICATIONS TO PHASE-SHIFT PHOTOLITHOGRAPHY

We describe a method of imaging the intensity profiles of light in nea r-field lithographic experiments directly by using a sensitive photore sist. This technique was applied to a detailed study of the irradiance distribution in the optical near field with contact-mode photolithogr aphy carried out by use of elastomeric phase masks. The experimental p atterns in the photoresist determined by scanning electron microscopy and atomic force microscopy were compared with the corresponding theor etical profiles of intensity calculated by use of a simple scalar anal ysis; the two correlate well. This comparison makes it possible to imp rove the theoretical models of irradiance distribution in the near fie ld. Analysis of the images highlights issues in the experimental desig n, provides a means for the optimization of this technique, and extend s its application to the successful fabrication of test structures wit h linewidths of similar to 50 nm. (C) 1998 Optical Society of America.