Semiconductor structure with controlled breakdown protection

Abstract

A power semiconductor device having internal circuits characterized by an electrical breakdown during one mode of operation is implemented with a protective circuit. The electrical breakdown is controllably induced to occur at the protective circuit thereby diverting any breakdown in the active circuits. In the preferred embodiment, the power device is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) in which the protective circuit is deposited as an annular diffusion ring having a shallow portion and a deep portion. The deep portion is higher in doping concentration than the shallow portion and includes a radius of curvature larger than the shallow portion. The radius of curvature of the deep portion can be adjusted to induce breakdown at or above the rated value of the MOSFET. The predetermined doping concentration of the deep portion can abort the breakdown prematurely to occur at the deep region instead of at the active circuits. Electrical contacts are tied to the annular diffusion ring to gravitate any charge carriers generated during the electrical breakdown so as to prevent the charge carriers from reaching the active circuits, thereby further ensuing no breakdown at the internal circuits.