CONDUCTION MECHANISM IN SILICON DIOXIDE LAYERS PRODUCED AT LOW-TEMPERATURES

The electrical conductivity of pyrolytic silicon dioxide films produced in the temperature range 150-400-degrees-C on silicon is studied. The hole character of the dielectric conductivity is shown by direct measurements using the method of electron and hole current separation in an MOS-transistor. The electron barrier on the Si-SiO2 boundary is estimated from the injection current-voltage curve (CVC) from accumulation of injected carriers in traps in the SiO2 at T = 77 K. The barrier value decreases with decrease in synthesis temperature (T(s)) of the dielectric from 3 (T(s) = 400-degrees-C) to 2.7 eV (T(s) = 150-degrees-C). It follows from analysis of field and temperature dependences of current that the electrical conductivity of SiO2 layers obtained at low temperatures can be described quite well by a "jump" conductivity mechanism through localized states within the SiO2 forbidden zone with a local center concentration of congruent-to 10(21) cm-3.