The differences between N‐ and N+ buried layers in improving the breakdown voltage of RESURF LDMOSFETs

Abstract

The differences between N-and N+ buried layers in improving the breakdown voltage of RESURF (reduced surface field) LDMOSFETs (lateral doublediffused metal-oxide-semiconductor field-effect transistors) are discussed in this paper. Two concise RESURF criteria for LDMOS with a low-doped fully depleted N-buried layer (NBL) and a highly doped nondepleted N+ floating layer (NFL) are developed by optimizing the lateral and vertical electric fields.The analytical solution quantitatively demonstrates the variation of the drift charge concentration and its dependence on the key NBL and NFL parameters. It also indicates that the NBL LDMOS achieves a superior tradeoff between specific on-resistance (R s,on )and breakdown voltage (BV) to the NFL LDMOS. The BV 2 /R s,on for NBL LDMOS is 3.1 MW/cm 2 , which is increased respectively by 93.8% and 40.9% compared with the single RESURF and NFL-LDMOS. K E Y W O R D Sbreakdown voltage, LDMOS, on resistance, RESURF