A general method for predicting the avalanche breakdown voltage of negative bevelled devices

Abstract

In this paper, the concept of an effective negative bevel angle is introduced. It is shown that the fraction of the ideal breakdown voltage that is attained for virtually any negatively bevelled diffused junction device is a single function of this effective bevel angle. These results can be used to calculate the breakdown voltage for diffused junction devices over the range of commonly used negative bevels. The effective bevel angle is shown to be the product of the actual bevel angle and the square of the ratio of the depletion width on the lightly and heavily doped sides of the junction for the ideal device at breakdown. Consideration is also given to abrupt junction devices. In the final section, an approximate means for correcting these results for variations in the passivant dielectric constant and the introduction of surface charge is presented.