Optimization of Guard Ring Structures to Improve Latchup Immunity in an 18 V DDDMOS Process

The optimization of guard ring structures to improve latchup immunity in an 18 V double-diffused drain MOS (DDDMOS) process with the DDDMOS transistors has together been investigated in a silicon test chip. The layout parameters including the anode-to-cathode spacing and the guard ring width are also studied to seek their impacts on latchup immunity. The measurement results demonstrated that the test devices isolated with the specific guard ring structure of n-buried layer can highly improve the latchup immunity. The suggested guard ring structures can be applied to the high-voltage circuits in this 18 V DDDMOS process to meet the new Joint Electron Device Engineering Council standard (JESD78D) with the trigger current of over ±200 mA.