Early detection of electrical defects in deep trench capacitors using voltage contrast inspection

Abstract

Improvement of learning cycle time and mean time to detect issues is integral to keeping up with the increasing pace needed in semiconductor technology development. Use of electron beam voltage contrast inspection as an early assessment of electrical defectivity of embedded dynamic random access memory in IBM's deep trench capacitor technology allows for detection of all major initial processing electrical defects months before conventional techniques. Product-like and specially designed on chip diagnostic structures are inspected as soon as active layer patterning and isolation is complete. This enables much earlier identification of electrical defectivity. Examples discussed include electrically open single connections, electrical short circuits to neighboring cells in an array, and cells that have short circuits to the silicon substrate. Physical failure analysis and correlation to other in-line measurement and electrical test signals were performed to verify the voltage contrast inspection results. Robust and reliable results enable regular use of this technique to assess electrical health of critical structures earlyin the process sequence on and to facilitate increased yield improvement learning cycles beyond what is otherwise possible.

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

“…Previously, a methodology for detecting EDRAM failure mechanisms using test structures and voltage contrast (VC) inspection was described for a planar technology [3]. FINFET technology presents a number of major new complexities including a) the risk of DT to DT shorts due to EPI growth on the fins which occurs after formation of the gates and, b) less spacing between elements.…”