Diamond-shaped body contact for on-state breakdown voltage improvement of SOI LDMOSFET

Abstract

In this paper, we report a diamond-shaped body contact (DSBC) for silicon-on-insulator (SOI) LDMOSFET. Several DSBC devices along with conventional body contact (CBC) structures are laid out using 0.35μm SOI MOSFET foundry process. The DSBC device is designed using the same standard layers as in the CBC structure and the contact layout is adapted to process design rules. Experimental characterization of the CBC and DSBC devices in terms of off-state breakdown voltage (BVoff), on-state breakdown voltage (BVon), on-resistance (Ron) and device foot print showed 19% improvement in BVon compared DSBC device with that of the CBC structure. BVoff and Ron of both of the devices are identical. The device foot print is smaller in DSBC device by 11% compared with that of the CBC structure leading to enhanced “On-resistance×Area” figure of merit where smaller high voltage SOI LDMOSEFT reduces the area and cost of power integrated circuits. In order to explain BVon improvement of DSBC structures, three-dimensional (3-D) device simulation is carried out to clarify the lateral BJT action and breakdown mechanism. It is demonstrated that the number of P+ diffusions in DSBC device can be increased to improve BVon without increasing “On-resistance×Area”. The on-state breakdown voltage improvement and area efficiency of the diamond-shaped body contact proposes it as a promising candidate for reliable operation of SOI LDMOSFET.