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.