In-line Small-Spot X-Ray Fluorescence Assessment of Electroplating and Chemical Mechanical Polishing

In this work we assessed in-line copper thickness evolution on patterned wafers during electroplating (ECD) and chemical mechanical polishing (CMP) steps by means of a novel high-resolution technique based on small-spot X-ray fluorescence ( μ-XRF). Copper thickness on patterned structures, as measured by μ-XRF, provided excellent correlation with cross-sectional scanning electron microscopy (SEM) and electrical resistance data. In addition, measurements accurately captured process signatures and pattern dependencies from ECD and CMP processes. μ-XRF shows a great potential as an in-line back-end-of-line metrology for advanced technology nodes.