New Superjunction LDMOS Breaking Silicon Limit by Electric Field Modulation of Buffered Step Doping

TLDR: In this article, a step doping buffered layer under the super junction LDMOS was proposed to obtain the low loss for the highvoltage region, which improved the breakdown voltage (BV) and average lateral electric field.

Abstract: A new superjunction LDMOS (SJ-LDMOS) is proposed with the step doping buffered layer under the SJ layer to obtain the low loss for the high-voltage region. The substrate-assisted depletion effect, which results from the p-type substrate for the n-channel SJ-LDMOS, has been eliminated by the step doping buffer layer. By the effect of the electric field modulation, a more uniform lateral electric filed is obtained due to the new high-electric field peaks introduced by the buffered step doping, which improves the breakdown voltage (BV) and average lateral electric field. Using ISE simulation, the BV of proposed SJ-LDMOST is increased by $\sim 50$ % than that of the conventional LDMOS, and improved by $\sim 32$ % than that of buffered SJ-LDMOS. The lateral average electric field is increased to 19 V/ $\mu $ m in the high-voltage region The experimental ${R} _{\mathbf {\mathrm{{\scriptstyle ON}},{\textrm sp}}}$ of the proposed SJ-LDMOS is 241 m $\Omega \,\cdot $ $\mathrm{cm}^{\mathrm {\mathbf {2}}}$ with a BV of 368 V, breaking the silicon limit relationship for ${R} _{\mathrm{{\scriptstyle ON}},\textrm {sp}}$ of 71.8 m $\Omega ~\cdot ~\mathrm{cm}^{\mathrm {\mathbf {2}}}$ with the BV of 242 V in the conventional LDMOS with the same drift region length The merit of BV/ $R _{\mathrm{{\scriptstyle ON}},\textrm {sp}}$ is 15.3 for the proposed SJ-LDMOS compared with that of 3.4 for the conventional LDMOS.