<title>Light-scattering-based micrometrology</title>

Abstract

Optical scatterometry, defined as the characterization of surfaces via diffracted light analysis, has been shown to be an attractive tool for the metrology of microlithographic structures. To tackle the inverse scattering problem, advanced data analysis schemes have been developed. This paper illustrates the application of light scattering to characterize developed resist lines in terms of multi- parameter measurements. Additionally, the depth prediction and the width prediction of special silicon concentration profiles, embedded in a plane resist layer, are reported. Substantial accuracy gains have been achieved by using partial least squares (PLS) regression along with quasi- nonlinear data preparation techniques, including range splitting or enhanced quadratic and cubic approaches. Moreover, a combination of PLS and minimum mean square error methods enables rapid and nearly arbitrarily accurate measurements.