The mechanism of self-healing electrical breakdown in MOS structures

The mechanism of single-hole and propagating breakdown is investigated in metal-oxide-silicon capacitors with nonshorting breakdown, the substrate resistivity varying from 10^-3to 10³Ω-cm. Magnitude of destruction of single-hole breakdowns and duration of breakdown event depend strongly on polarity and resistivity of file substrate and the duration varies from nano- to microseconds. Average temperature of the metal on breakdown was found spectroscopically to be 4000 to 4500°K. Breakdown starts on electric field induced thermal instability at a flaw in the dielectric and a hole is evaporated through oxide and metal. In continuation, the capacitor discharges into the flaw, causing relatively large destruction in the metal. Duration of breakdown process could be estimated in samples in which, on breakdown, no impact ionization occurs in the silicon. Destruction is due to joule heat and arc action; current densities approaching 10¹⁰A/cm²were observed. Magnitude of destruction was calculated for varying voltages, polarities, and types of substrates, and reasonable agreement was found with observed magnitudes. Table VI summarizes variation of breakdown properties with substrate resistivity and polarity. Propagating breakdown occurs only at highest voltages. Relative to single-hole breakdown, the destruction is large and energy for destruction is supplied directly from source. Mechanisms of three types of propagating breakdowns are interpreted, those propagating at neighboring sites, those progressing by an arc, and those propagating by gas breakdown through existing breakdown holes.