Location of interconnect defects using focused ion beam (FIB) induced voltage contrast and subsequent auger electron analysis of in-situ FIB cross sections in the physical electronics 200/300-mm SMART-tool

It is shown that the focused ion beam in the Physical Electronics SMART-Tool can be used to create the conditions needed to locate interconnect defects by voltage-contrast analysis. The SMART-Tool is designed for the analysis of small defects on full wafers by Auger electron spectroscopy. These defects are typically located using a defect coordinate map from a light-scattering based inspection tool. The SMART-Tool can be equipped with a focused ion beam for cross-sectioning defects. Stand-alone focused ion beam tools have been used to locate defects by voltagecontrast analysis. Unlike stand-alone tools, the ion beam in the SMART-Tool is situated off the surface normal. This does not hinder its ability to ground interconnect parts to the substrate, creating the conditions for passive voltagecontrast imaging. A defective via chain, identified by high resistivity on parametric test, was grounded to the substrate by focused ion beam milling in the SMART-Tool. The defective via was then identified by voltage contrast in images. The defect was marked and cross-sectioned by the focused ion beam and analyzed by Auger electron spectroscopy, all in the SMART-Tool without breaking or repositioning the wafer. Studies suggest that unbroken wafers can be returned to the manufacturing line to complete processing after focused ion beam milling without compromising unaffected die. Thus, this type of interconnect defect analysis can be performed on defective die without sacrificing non-defective die on the same wafer.