In-line characterization of EDRAM for a FINFET technology using VC inspection

An E-beam voltage contrast inspection methodology involving multiple inspection points has been created to support development of the EDRAM module for a recent FINFET technology. This methodology provides within-sector feedback for a wide range of defect types enabling fast turn-around of split experiments and early detection of process excursions. Most defectivity affecting EDRAM is buried and therefore not detectable with broad beam plasma inspection. The EDRAM module is first in the process sequence for this FINFET technology. Without E-beam inspection, the first opportunity for defectivity feedback would be metal 1 test, which is months later in the process sequence. While direct E-beam inspection of functional EDRAM is a key part of this methodology, many defect types cannot be detected directly on functional SRAM. Special voltage contrast test structures were designed to monitor these defect types. The key defect types and the strategy used to detect each of them is described in detail in this paper. Select split experiment and process excursion data are used to illustrate the impact of the methodology.