STUDY OF INTERFACE TRAP GENERATION CAUSED BY DYNAMIC FOWLER-NORDHEIM (FN) STRESS ON nMOSFETs

In this work, gate dielectric degradation under dynamic Fowler-Nordheim (FN) stress is studied. A novel interface characterization technique, direct-current current-voltage (DCIV) technique, is used to measure the interface trap generation caused by dynamic FN stress. The dependence of interface trap generation on stress time is always found to follow a power-law, which is similar to the situation for DC stress. A suppression of interface trap generation is observed with the increase of nitrogen concentration in the nitrided gate oxide. For both positive unipolar and bipolar stresses, with the increase of the frequency of stress pulses interface trap generation increases and increase of nitrogen concentration could reduce this dependence of interface trap generation on the stress frequency. For negative unipolar stress, an abnormal phenomenon, i. e. a sharp increase in the DCIV current in the frequency range of about 1K-8KHz, is observed. This phenomenon is much more significant for lower nitrogen concentration. The reason of this phenomenon is still not clear yet. Key-Words: nitrided oxide, dynamic Fowler-Nordheim stress, interface trap generation, DCIV technique, power law behavior.