Abstract

Measurement of critical dimensions is accomplished by means of thresholding the intensity profile of an image. What we present here is an alternative technique that utilizes the spectrum of the intensity profile in order to perform these measurements. It is well known that as we move away from the object we lose important information that the evanescent modes contain (e.g., near field microscope). As feature sizes are reduced, limitation in the number of propagating modes that are gathered is a fundamental problem for classical optical microscopes. Utilizing the fact that the remaining frequency components still have valuable information, we performed simulations by utilizing a strip and a relief grating. The results obtained are very good even for submicrometric features in the case of the strip gratings. For the case of a 90° sidewall angle, results are very promising. Studies on structures that have side-wall angles that are different from 90° are under way.

© 1992 Optical Society of America