Step drift doping profile for high voltage DI lateral power devices

The cell pitch of high voltage lateral power devices determines many important device performance specifications such as the area of the chip, on-state voltage drop and the maximum controllable current. Since the cell pitch of lateral power devices is determined by the long drift region lengths required to support high voltages in accordance with the RESURF principle, it is desirable to have a uniform lateral electric field distribution in the drift region to minimize the drift region length for a device with a given breakdown voltage. It is generally assumed that the breakdown voltage of DI RESURF devices scales up linearly with increasing drift region length till a limit associated with vertical breakdown is reached. However, 2D numerical simulations of the breakdown of DI PIN diodes indicate non-ideal electric field distribution in the drift region. Two techniques have been studied for achieving a more uniform electric field distribution in the drift region for DI lateral power devices. One technique involves the use of a SIPOS field plate over the drift region to spread the electric field uniformly. The other technique involves tailoring the drift region doping profile, so that the drift region charge increases linearly from the anode end to the cathode end.