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

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 ~50% than that of the conventional LDMOS, and improved by ~32% than that of buffered SJ-LDMOS. The lateral average electric field is increased to 19 V/μm in the high-voltage region The experimental RON,sp of the proposed SJ-LDMOS is 241 mΩ · cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with a BV of 368 V, breaking the silicon limit relationship for R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON,sp</sub> of 71.8 mΩ · cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with the BV of 242 V in the conventional LDMOS with the same drift region length The merit of BV/R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON,sp</sub> is 15.3 for the proposed SJ-LDMOS compared with that of 3.4 for the conventional LDMOS.