Trends in the ultimate breakdown strength of high dielectric-constant materials

The ultimate breakdown strength E/sub bd/ of a dielectric material is found to decrease as the dielectric-constant k increases. A thermochemical description of the ultimate breakdown strength of high-k dielectrics suggests that E/sub bd/ should reduce approximately as (k)/sup -1/2/ over a wide range of dielectric materials while the field-acceleration parameter /spl gamma/ should increase in similar but inverse manner. New time-dependent dielectric breakdown (TDDB) data are presented over a wide range of dielectric materials and E/sub bd/ was found to decrease as (k)/sup -0.65/ while /spl gamma/ increases as (k)/sup 0.66/. The good agreement between thermochemical theory and high-k TDDB observations suggests that the very high local electric field (Lorentz-relation/Mossotti-field) in high-k dielectrics tends to distort/weaken the polar molecular bonds making them more susceptible to bond breakage by standard Boltzmann processes and/or by hole-capture and thus lowers the breakdown strength.