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The need to characterize line edge and line width roughness in patterns with sub‐50 nm critical dimensions challenges existing platforms based on electron microscopy and optical scatterometry. The development of x‐ray based metrology platforms provides a potential route to characterize a variety of parameters related to line edge roughness by analyzing the diffracted intensity from a periodic array of test patterns. In this study, data from a series of photoresist line/space patterns featuring programmed line width roughness are measured by critical dimension small angle x‐ray scattering (CD‐SAXS). For samples with designed periodic roughness, CD‐SAXS provides the wavelength and amplitude of the periodic roughness through satellite diffraction peaks. For real world applications, the rate of decay of intensity, termed an effective “Debye‐Waller” factor in CD‐SAXS, provides an overall measure of the defects of the patterns. CD‐SAXS data are compared to values obtained from critical dimension scanning electron microscopy (CD‐SEM). Correlations between the techniques exist, however significant differences are observed for the current samples. A tapered cross sectional profile provides a likely explanation for the observed differences between CD‐SEM and CD‐SAXS measurements.

In semiconductor electronics applications, line edge and linewidth roughness are generally measured using a root mean square (RMS) metric. The true value of RMS roughness depends upon the length of edge or line that is measured and the chosen sampling interval. Additionally, the true value is obscured by a number of measurement errors: Different finite‐length sections of line have randomly differing roughnesses, producing a sampling error, the expected magnitude of which depends upon the length of line that is sampled and details of its roughness power spectrum. Noise in the microscope images from which roughness is computed results in both a random measurement error and a non‐random measurement bias. These issues and proposed solutions in the literature are reviewed. It is also suggested that there may be a plausible role for non‐RMS metrics, for example estimation of the likelihood of width or edge position extremes based upon direct measurements of the roughness amplitude density function.