Explosion Physics Laboratory
or to A.L.Kupershtokh Abstract of report at 1998 IEEE International Symposium on
Electrical Insulation, 7-10 June 1998, Washington, DC, USA. Full text of presentation.
There are two mechanisms of breakdown inception in liquids. The first one is the ionization mechanism and the second one is the "gas bubble". Competition of these two mechanisms in liquids complicates interpretation of experimental results. Solid amorphous layers are similar in properties to liquid dielectrics. At the same time, solid amorphous materials are more uniform than liquids and do not have impurities such as vapor bubbles. This fact allows one to use such films for investigation of possible breakdown mechanisms over a wide range of external conditions. One important characteristic indicating a physical mechanism of breakdown is the statistical lag time of its inception.
An experimental investigation of breakdown in metal-oxide-semiconductor (MOS) structures was carried out. MOS samples were composed of a silicon substrate, covered with a thin (about 100 nm) amorphous layer of thermal silicon oxide, on which many square Al electrodes (0.7x0.7 mm2) were deposited.
Constant voltage was applied to the sample and the statistical lag time of breakdown was measured. The electric field in the dielectric was up to 9·106 V/cm. The shift of the flat band voltage after several breakdowns was also measured. Positive charge accumulation in the dielectric film was found.
The results show that thin amorphous solid films and liquid dielectrics have many similar breakdown features.
This work was supported in part by the Russian Foundation for Basic Research under grant No. 97-02-18416.
Full text of presentation.