Nonplanar high-k dielectric thickness measurements using CD-SAXS

Non-planar transistor architectures, such as tri-gates or "FinFETs", have evolved into important solutions to the severe challenges emerging in thermal and power efficiency requirements at the sub-32 nm technology nodes. These architectures strain traditional dimensional metrology solutions due to their complex topology, small dimensions, and number of materials. In this study, measurements of the average dielectric layer thickness are reported for a series of structures that mimic non-planar architectures. The structures are line/space patterns (≈ 20 nm linewidth) with a conformal layer of sub-15 nm thick high-k dielectric. Dimensions are measured using a transmission X-ray scattering technique, critical dimension small angle X-ray scattering (CD-SAXS). Our test results indicate that CD-SAXS can provide high precision dimensional data on average CD, pitch, and high-k dielectric layer thickness. CD-SAXS results are compared with analogous data from both top-down scanning electron microscopy and cross-sectional transmission electron microscopy. In addition, we demonstrate the capability of CD-SAXS to quantify a periodic deviation in pitch induced by an imperfection in the phase shift mask.