Dielectric breakdown prediction and dielectric breakdown life-time prediction using iterative voltage step stressing
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorMikihiro Kimura
Life of this patent
Estimating the term…
Abstract
An accurate dielectric breakdown prediction method and a prediction method in which accurate time dependent dielectric breakdown (TDDB) characteristics can be obtained on the basis of dielectric breakdown prediction by a step stress method are provided. In this method, dielectric breakdown is predicted on the basis of a plurality of reference currents in accordance with an applied voltage, or a reference current I.sub.cr is varied as the function of the applied voltage. In the step stress TDDB prediction, a Chen-Holland-Hu model or improved Chen-Holland-Hu model is employed. Since TDDB characteristics can be obtained from only dielectric breakdown prediction, this method is advantageous for early reliability prediction.
Claims4
A dielectric breakdown life-time prediction apparatus comprising:
- a pair of electrodes placed across a specimen;
- a step voltage applying apparatus for applying an electric-field intensity E.sub.i to said pair of electrodes for a step time .DELTA.t.sub.i ;
- a current meter for measuring electric current I flowing through said specimen;
- a reference current generator for generating a dielectric breakdown reference current I.sub.cr whose value varies as a function of a voltage applied to the specimen;
- a current comparator for comparing the value of current flowing through said specimen with the value of said dielectric breakdown reference current;
- and
- a counter for counting the number of steps N until said specimen breaks down;
- and
- a dielectric breakdown life-time calculation apparatus for determining the dielectric breakdown life-time t.sub.BD from the following equation (1) when there is one type of acceleration factor G in the entire area of the electric-field intensity E.sub.G :
- ##EQU10##
A dielectric breakdown prediction method comprising the steps of:
- applying an electric-field intensity E.sub.i across a specimen for a step time .DELTA.t.sub.i ;
- measuring electric current I flowing through said specimen;
- generating a dielectric breakdown reference current I.sub.cr whose value varies as a function of a voltage applied to the specimen;
- comparing the value of current flowing through said specimen with the value of said dielectric breakdown reference current;
- counting the number of steps N until said specimen breaks down;
- and
- determining an acceleration factor G and a dielectric breakdown life-time t.sub.BD from the following equation (1) when there is an acceleration factor G in the entire area of the electric-field intensity E.sub.G :
- ##EQU11##
Dependencies are inferred from the claim text.