Patents Represented by Attorney Michael A. Flehr, Hohbach, Test, Albritton & Herbert Kaufman
  • Patent number: 5638006
    Abstract: An IC wafer containing thin oxide is fabricated to include at least two differentially-sized plate areas that may be upper plates of capacitors, or gates of associated MOS transistors. Before testing, the thin gate oxide underlying these plate areas is intentionally stressed by applying a stress current between these plates and the substrate. The stress current magnitude is scaled to the plate area such that each plate sees a substantially constant current density. Because weak oxide defects occur somewhat uniformly throughout the thin oxide, a larger plate or gate will overlie more weak oxide defects than will a plate or gate. If wafer test leakage current between the larger plate or gate and substrate exceeds leakage current between the smaller plate or gate and substrate, weak oxide is indicated because the defect is area dependent. By contrast, charge-induced damage is substantially independent of the areas of the plates or gates, due to the scaling of the stress-inducing currents.
    Type: Grant
    Filed: May 30, 1995
    Date of Patent: June 10, 1997
    Assignee: VLSI Technology, Inc.
    Inventors: Subhash R. Nariani, Calvin T. Gabriel