Critical dimension measurement: from synchrotron small angle x-ray scattering to industrial optical scatterometry techniques

Abstract

Critical Dimension (CD) control is essential in the semiconductor industry and becomes more challenging as photolithography limits keep getting pushed to reach technological nodes smaller than 10 nm. To ensure quality and control of the processes, it becomes necessary to explore new metrology techniques. In this sense, Critical Dimension Small-Angle X-ray Scattering (CDSAXS) has been identified as a potential candidate to determine the average shape of a line grating with a sub-nanometric precision. In this paper we benchmark the CDSAXS results to Optical Critical Dimension (OCD), Critical Dimension Scanning Electron Microscopy (CDSEM) and Transmission Electron Microscopy (TEM) measurements previously collected from industrial metrology tools at manufacturing line and in characterization laboratory. Emphasis is placed on the model used for CDSAXS and how to improve it. We discuss the differences between all these multi-scale and multi-physics techniques, and question our capacity to compare them.