Showing papers by "S.E. Holland published in 1985"

Electrical breakdown in thin gate and tunneling oxides

Abstract: The breakdown of thin oxides (7.9-32 nm) subjected to high-field current injection is investigated in this study. The physical mechanism of breakdown is found to be localized field enhancement at the cathode interface due to hole trapping. The source of this hole trapping is believed to be impact ionization in the SiO 2 . A quantitative model for oxide breakdown based on impact ionization and hole trapping at the cathode is presented and shown to agree well with the experimental J - t and time-to-breakdown, (t BD ) results. We observe that log t BD varies linearly with 1/ E rather than with E as commonly assumed. The field acceleration factor, i.e., the slope of the log t BD versus 1/ E plot, is approximately 140 decades per centimeter per megavolt for the 7.9 nm oxide, with approximately 25 percent of this coming from the field dependence of the impact ionization coefficient and the remainder from the Fowler-Nordheim current dependence on 1/ E . Based on this model, oxide wearout performance might be improved by process changes that reduce interface hole trapping, such as radiation-hard processing, in addition to the reduction of particulate contamination and crystal defects.

Electrical Breakdown in Thin Gate and Tunneling Oxides

Abstract: The breakdown of thin oxides (7.9-32 nm) subjected to high-field current injection is investigated in this study. The physical mechanism of breakdown is found to be localized field enhancement at the cathode interface due to hole trapping. The source of this hole trapping is believed to be impact ionization in the SiO/sub 2/. A quantitative model for oxide breakdown based on impact ionization and hole trapping at the cathode is presented and shown to agree well with the experimental J - t and time-to-breakdown, (t/sub BD/) results. We observe that log t/sub BD/ varies linearly with 1/E rather than with E as commonly assumed. The field acceleration factor, i.e., the slope of the log t/sub BD/ versus 1/E plot, is approximately 140 decades per centimeter per megavolt for the 7.9 nm oxide, with approximately 25 percent of this coming from the field dependence of the impact ionization coefficient and the remainder from the Fowler-Nordheim current dependence on 1/E. Based on this model, oxide wearout performance might be improved by process changes that reduce interface hole trapping, such as radiation-hard processing, in addition to the reduction of particulate contamination and crystal defects.

A quantitative physical model for time-dependent breakdown in SiO2

Abstract: A quantitative physical breakdown model for thin SiO2 is developed. The physical mechanism responsible fcor oxide breakdown has been reexamined and found to be hole trapping at localized areas. A quantitative model is built on this physical understanding of the wearout mechanism. Using this model, which considers electron injection, hole generation and charge trapping during electrical stresses and their effects on oxide I-V characteristics, all commonly used reliability tests can be simulated. Results are presented for constant-voltage, constant-current and ramp-voltage stress tests. One important result of the model is that log(tBD) of constant-voltage accelerated test is a linear function of 1/Eox, not Eox. The elctcric field dependence of log(QBD) is the same as that of the hole generation rate ?. The correlation between ramp-voltage stress and constant-voltage stress is treated in detail, and an analytical expression relating the two is presented. This correlation provides a method and a theoretical basis for substituting the time-consuming tBD test with the simple ramp-voltage breakdown test.