Multitechnique metrology methods for evaluating pitch walking in 14 nm and beyond FinFETs

Abstract

Integrated circuits from 22-nm node and beyond utilize many innovative techniques to achieve features that are well beyond the resolution limit of 193-nm immersion lithography. The introduction of complex three-dimensional structures in device design presents additional challenges that require more sophisticated metrology with high accuracy and precision. One such example is pitch walking induced by multiple-patterning techniques. Quantification of pitch walking has traditionally been a challenge. We present two ways of detecting pitch walking using optical and x-ray techniques. In scatterometry, this work investigates the feasibility of nonorthogonal azimuth angle spectroscopic reflectometry setups for fin pitch walking measurements, which is useful for in-line monitoring in 14-nm node microelectronics manufacturing. Simulations show a significant improvement in pitch walking sensitivity using 45-deg azimuth scan. Other relevant considerations for pitch walking modeling in scatterometry, such as parameter correlations, are also discussed. Another approach is using high-resolution x-ray diffraction (HRXRD) to measure the diffraction peaks from crystalline fins. The onset of pitch walking is determined by the appearance of a shifted subset of peaks in the diffraction spectrum. Information about the fin profiles, e.g., sidewall angle, critical dimension, height, and pitch walking, can be obtained from the resultant diffraction pattern. Note that in HRXRD measurements, each critical parameter is a unique element in the Reciprocal Space Map (RSM) and no correlations between parameters exist. We will discuss the results from measurements using the two techniques and how the combination of the two techniques can give complete information about the fins needed for in-line monitoring.