Experimental verification of high numerical aperture effects in photoresist

Abstract

Verification of the two-beam and three-beam models developed in Chapter IV has been shown through sets of experiments which use a unique decoration technique to examine cross-sections ofthe image within photoresist. The use of photoresist as a detector ofthe image record is explained through a simple photoresist development model that approximates the photoresist behavior. Two-beam interference experiments with plane waves at 0.85 NA show strong differences between the S and P polarizations. Experiments that use reflective underlayers show that S polarization produces elliptical features while P polarization gives rectangular features. Since these features depend on the extent of reflectivity of the z component, further experiments demonstrate the reduction ofthese features by minimizing the reflectivity. This is shown to agree with simulations. Three-beam interference experiments show that the vector effects present in the two-beam configuration are diminished. The polarization effects, due to the obliquity of the ±1st orders, are greatly reduced by the addition of a strong 0th order. These effects increase as the relative power of the 0th order is diminished. The effects of focus through the film are seen as an image inversion from the top surface to the bottom ofthe film.