Influence of a shallow p+ offset region on a novel edge termination technique using lightly doped p-rings

In this paper, for the first time, a novel `volumetric´ edge termination structure using minimally sized lightly doped p-rings is presented. The addition of a shallow p⁺ region, offset from the centre of each well towards the main junction, reduces the peak electric field at the surface and provides immunity to interface oxide charges. An alternative structure with metal field plate contacted to a p region centred within the p-well enables the peak electric field at each ring to be further reduced. As a result 90% of the plane parallel breakdown voltage can be achieved by increasing the number of rings. The influence of oxide thickness and the interface charge on the breakdown voltage of all three edge terminations has been analysed in detail