The Boundary between Hard- and Soft-Breakdown in Ultra-Thin Silicon Dioxide Films
- PDF / 1,040,937 Bytes
- 7 Pages / 415.8 x 637.2 pts Page_size
- 43 Downloads / 143 Views
ABSTRACT The dielectric breakdown is an irreversible and transient process, and it is difficult to understand its dynamic characteristics. We notice that the post-breakdown electrical properties of silicon dioxide films may include much information on the dielectric breakdown mechanism. First, the resistance of silicon dioxide films after the dielectric breakdown is statistically investigated, and then this analysis is applied to differentiate the hard- from the soft-breakdown. In particular, we discuss the critical dependence of the boundary between the hard- and softbreakdown on the discharging time constant as well as the discharging energy at the breakdown, concerning the formation of the conductive filament in the insulator silicon dioxide films. It should be noted that the ratio of the soft- to the hard-breakdown changes in terms of the statistical distribution in the case that the growth parameters and the measurement conditions are changed. In partcular, the external inductance effect to modify the discharging time constant in the MOS circuit is discussed. The thickness limitation of the silicon dioxide film in the roadmap is in this transition region, and this fact will be of essential importance in the assessment of the reliability and the process control of silicon device fabrication in sub-5nm silicon dioxide regime.
INTRODUCTION
The gate insulator thickness has been thinned to the atomic scale [1], according to the scaling rule, or more recently to the "Roadmap" [2]. Many papers have reported the microscopic mechanisms of SiO 2 deterioration. In many cases, the mechanism describes the distribution center of failures. However, the reliability should be described in terms of the statistics, because the reliability behaves intrinsically in a statistical sense. In the thin oxide region, it is characteristic that the soft-breakdown, in which the oxide breakdown does not show a significant jump of conductance, appears and that both hard- and soft-breakdown coexist. To understand the difference of hard- and soft-breakdown, we noted the statistics of the postbreakdown resistance, Rbd, for the first time, as well as Qbd. We think that the resistance of oxide after the breakdown might be determined by the filament size of the conduction path in SiO 2, which is not the conductive spot connection but is a filament formed by the power injection just at the breakdown. From this point, we think that the difference between hard- and soft-breakdown may be related to the energy dissipation process at the dielectric breakdown. Consequently, we experimentally demonstrate that the discharging energy and the time constant of the energy dissipation in the MOS structure should be considered in the thin oxide breakdown. This analysis will also facilitate the understanding of the SiO 2 dielectric breakdown mechanism by providing a new set of information on that.
323
Mat. Res. Soc. Symp. Proc. Vol. 592 © 2000 Materials Research Society
EXPERIMENTAL RESULTS AND DISCUSSION The devices used in this study were n+poly-Si capaci
Data Loading...
