Detailed comparison of experiment and theory of passivation ring structures for power devices

This work shows that using a combination of tightly controlled diffusions and NTD silicon with small resistivity fluctuations passivation schemes using a series of rings (Kao´s rings) can yield significantly higher breakdown voltages than would be expected on the basis of the conventionally used ionisation coefficients of Overstraeten and de Man. By measuring breakdown conditions on a range of well defined structures it has been shown that the behaviour of such systems in the range 1200 to 1600V can be predicted using a combination of a 2D numerical analysis (using the general-purpose 1-3D off-state package TRIPOS (1)) and Lee´s (2) avalanche ionisation coefficients.