Integrated Thyristor Switch Structures for Capacitor Discharge Application

A thyristor switch circuit for capacitor discharge application, of which the equivalent circuit includes a resistor between cathode and gate of a reverse-conducting thyristor and an avalanche diode anti-parallel between its anode and gate to set thyristor tum-on voltage, is monolithically integrated by planar process with AVE double-implantation method. To ensure a lower breakdown voltage of the avalanche diode for thyristor tum-on than the break-over voltage of the thyristor, $p^+$ wells on thyristor p base layer are made by boron implantation/drive-in for a steeper doping profile with higher concentrations while rest p layers of thyristor and free-wheeling diode parts are formed with Al implantation/drive-in for a doping profile of lower steepness. The free-wheeling diode part is isolated from the thyristor part by formation of separated p-well emitter for suppressing commutation between them, which is achieved during the formation of thyristor p-base layer.