For a recent replacement metal gate (RMG) technology using a SOI substrate, residue from the dummy gate formed a defect that affected the RMG formation. In this FINFET technology, the high aspect ratio of the gate makes removing the dummy gate very difficult. Residue is left behind, especially in multi-fin structures. This residue was poorly detected by existing Broad-Band-Plasma inspection and thus required Electron Beam Inspection. However, this physical inspection is challenging due to high aspect ratio of the gate and an insulating wafer surface. The defect was verified using TEM, and careful sample prep is shown to be critical to verify the defect. The high aspect ratio and insulating sample in a charged-particle inspection is investigated with Monte-Carlo (MC) simulations.

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