The new high voltage level up shifter for HVIC

A new high voltage level up shifter for high-voltage integrated circuits (HVIC) is presented that combines the optimized shape of a high doping concentration layer (N+ buried layer) and low doping isolation. In order to realize the high voltage level up shifter for HVIC, not only the P-doping level for isolation area but also the shape of N+ buried layer is very important. In P-doping level, it is hard to find the optimized condition. If the doping level is higher than proper condition, the breakdown voltage is lower than 600 V. In the opposite case, there is leakage currents between active to active area. After several experiments, one can find the optimized condition for P- isolation-around 8E12 ion/cm/sup 2/. Under the optimized Pisolation condition, the shape of the N+ buried layer decides the breakdown voltage of the level up shifter. According to experimental result, as the edge radius of the N+ buried layer increases from 0 /spl mu/m to 100 /spl mu/m, the breakdown voltage of the level up shifter increases from 355 V to 645 V under the same vertical structure and process conditions.